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Blood

Blood

Overview






Blood is a specialized bodily fluid in animal
Animal
Animals are a major group of multicellular, eukaryotic organisms of the kingdom Animalia or Metazoa. Their body plan eventually becomes fixed as they develop, although some undergo a process of metamorphosis later on in their life. Most animals are motile, meaning they can move spontaneously and...

s that delivers necessary substances such as nutrients and oxygen
Oxygen
Oxygen is the element with atomic number 8 and represented by the symbol O. Its name derives from the Greek roots ὀξύς and -γενής , because at the time of naming, it was mistakenly thought that all acids required oxygen in their composition...

 to the cell
Cell (biology)
The cell is the basic structural and functional unit of all known living organisms. It is the smallest unit of life that is classified as a living thing, and is often called the building block of life. The Alberts text discusses how the "cellular building blocks" move to shape developing embryos....

s and transports metabolic waste
Metabolic waste
Metabolic wastes or excretes are substances left over from excretory processes, which cannot be used by the organism , and must therefore be excreted. This includes nitrogen compounds, water, CO2, phosphates, sulfates, insoles, medicals, food additives etc. Animals treat these compounds as excretes...

 products away from those same cells.

In vertebrate
Vertebrate
Vertebrates are animals that are members of the subphylum Vertebrata . Vertebrates are the largest group of chordates, with currently about 58,000 species described. Vertebrates include the jawless fishes, bony fishes, sharks and rays, amphibians, reptiles, mammals, and birds...

s, it is composed of blood cells suspended in a liquid
Liquid
Liquid is one of the three classical states of matter . Like a gas, a liquid is able to flow and take the shape of a container. Some liquids resist compression, while others can be compressed. Unlike a gas, a liquid does not disperse to fill every space of a container, and maintains a fairly...

 called blood plasma
Blood plasma
Blood plasma is the straw-colored liquid component of blood in which the blood cells in whole blood are normally suspended. It makes up about 55% of the total blood volume. It is the intravascular fluid part of extracellular fluid...

. Plasma, which constitutes 55% of blood fluid, is mostly water (92% by volume), and contains dissipated proteins, glucose
Glucose
Glucose is a simple sugar and an important carbohydrate in biology. Cells use it as the primary source of energy and a metabolic intermediate...

, mineral ions, hormone
Hormone
A hormone is a chemical released by a cell or a gland in one part of the body that sends out messages that affect cells in other parts of the organism. Only a small amount of hormone is required to alter cell metabolism. In essence, it is a chemical messenger that transports a signal from one...

s, carbon dioxide
Carbon dioxide
Carbon dioxide is a naturally occurring chemical compound composed of two oxygen atoms covalently bonded to a single carbon atom...

 (plasma being the main medium for excretory product transportation), platelets and blood cells themselves.
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Encyclopedia






Blood is a specialized bodily fluid in animal
Animal
Animals are a major group of multicellular, eukaryotic organisms of the kingdom Animalia or Metazoa. Their body plan eventually becomes fixed as they develop, although some undergo a process of metamorphosis later on in their life. Most animals are motile, meaning they can move spontaneously and...

s that delivers necessary substances such as nutrients and oxygen
Oxygen
Oxygen is the element with atomic number 8 and represented by the symbol O. Its name derives from the Greek roots ὀξύς and -γενής , because at the time of naming, it was mistakenly thought that all acids required oxygen in their composition...

 to the cell
Cell (biology)
The cell is the basic structural and functional unit of all known living organisms. It is the smallest unit of life that is classified as a living thing, and is often called the building block of life. The Alberts text discusses how the "cellular building blocks" move to shape developing embryos....

s and transports metabolic waste
Metabolic waste
Metabolic wastes or excretes are substances left over from excretory processes, which cannot be used by the organism , and must therefore be excreted. This includes nitrogen compounds, water, CO2, phosphates, sulfates, insoles, medicals, food additives etc. Animals treat these compounds as excretes...

 products away from those same cells.

In vertebrate
Vertebrate
Vertebrates are animals that are members of the subphylum Vertebrata . Vertebrates are the largest group of chordates, with currently about 58,000 species described. Vertebrates include the jawless fishes, bony fishes, sharks and rays, amphibians, reptiles, mammals, and birds...

s, it is composed of blood cells suspended in a liquid
Liquid
Liquid is one of the three classical states of matter . Like a gas, a liquid is able to flow and take the shape of a container. Some liquids resist compression, while others can be compressed. Unlike a gas, a liquid does not disperse to fill every space of a container, and maintains a fairly...

 called blood plasma
Blood plasma
Blood plasma is the straw-colored liquid component of blood in which the blood cells in whole blood are normally suspended. It makes up about 55% of the total blood volume. It is the intravascular fluid part of extracellular fluid...

. Plasma, which constitutes 55% of blood fluid, is mostly water (92% by volume), and contains dissipated proteins, glucose
Glucose
Glucose is a simple sugar and an important carbohydrate in biology. Cells use it as the primary source of energy and a metabolic intermediate...

, mineral ions, hormone
Hormone
A hormone is a chemical released by a cell or a gland in one part of the body that sends out messages that affect cells in other parts of the organism. Only a small amount of hormone is required to alter cell metabolism. In essence, it is a chemical messenger that transports a signal from one...

s, carbon dioxide
Carbon dioxide
Carbon dioxide is a naturally occurring chemical compound composed of two oxygen atoms covalently bonded to a single carbon atom...

 (plasma being the main medium for excretory product transportation), platelets and blood cells themselves. Albumin
Albumin
Albumin refers generally to any protein that is water soluble, which is moderately soluble in concentrated salt solutions, and experiences heat denaturation. They are commonly found in blood plasma, and are unique to other blood proteins in that they are not glycosylated...

 is the main protein in plasma, and it functions to regulate the colloidal osmotic pressure
Osmotic pressure
Osmotic pressure is the pressure which needs to be applied to a solution to prevent the inward flow of water across a semipermeable membrane....

 of blood. The blood cells are mainly red blood cell
Red blood cell
Red blood cells are the most common type of blood cell and the vertebrate organism's principal means of delivering oxygen to the body tissues via the blood flow through the circulatory system...

s (also called RBCs or erythrocytes) and white blood cell
White blood cell
White blood cells, or leukocytes , are cells of the immune system involved in defending the body against both infectious disease and foreign materials. Five different and diverse types of leukocytes exist, but they are all produced and derived from a multipotent cell in the bone marrow known as a...

s, including leukocytes and platelet
Platelet
Platelets, or thrombocytes , are small,irregularly shaped clear cell fragments , 2–3 µm in diameter, which are derived from fragmentation of precursor megakaryocytes.  The average lifespan of a platelet is normally just 5 to 9 days...

s. The most abundant cells in vertebrate blood are red blood cells. These contain hemoglobin
Hemoglobin
Hemoglobin is the iron-containing oxygen-transport metalloprotein in the red blood cells of all vertebrates, with the exception of the fish family Channichthyidae, as well as the tissues of some invertebrates...

, an iron
Iron
Iron is a chemical element with the symbol Fe and atomic number 26. It is a metal in the first transition series. It is the most common element forming the planet Earth as a whole, forming much of Earth's outer and inner core. It is the fourth most common element in the Earth's crust...

-containing protein, which facilitates transportation of oxygen
Oxygen
Oxygen is the element with atomic number 8 and represented by the symbol O. Its name derives from the Greek roots ὀξύς and -γενής , because at the time of naming, it was mistakenly thought that all acids required oxygen in their composition...

 by reversibly binding to this respiratory gas and greatly increasing its solubility in blood. In contrast, carbon dioxide is almost entirely transported extracellularly dissolved in plasma as bicarbonate
Bicarbonate
In inorganic chemistry, bicarbonate is an intermediate form in the deprotonation of carbonic acid...

 ion.

Vertebrate blood is bright red when its hemoglobin is oxygenated. Some animals, such as crustacean
Crustacean
Crustaceans form a very large group of arthropods, usually treated as a subphylum, which includes such familiar animals as crabs, lobsters, crayfish, shrimp, krill and barnacles. The 50,000 described species range in size from Stygotantulus stocki at , to the Japanese spider crab with a leg span...

s and mollusks, use hemocyanin
Hemocyanin
Hemocyanins are respiratory proteins in the form of metalloproteins containing two copper atoms that reversibly bind a single oxygen molecule . Oxygenation causes a color change between the colorless Cu deoxygenated form and the blue Cu oxygenated form...

 to carry oxygen, instead of hemoglobin. Insect
Insect
Insects are a class of living creatures within the arthropods that have a chitinous exoskeleton, a three-part body , three pairs of jointed legs, compound eyes, and two antennae...

s and some mollusks use a fluid called hemolymph
Hemolymph
Hemolymph, or haemolymph, is a fluid in the circulatory system of some arthropods and is analogous to the fluids and cells making up both blood and interstitial fluid in vertebrates such as birds and mammals...

 instead of blood, the difference being that hemolymph is not contained in a closed circulatory system
Circulatory system
The circulatory system is an organ system that passes nutrients , gases, hormones, blood cells, etc...

. In most insects, this "blood" does not contain oxygen-carrying molecules such as hemoglobin because their bodies are small enough for their tracheal system
Invertebrate trachea
The invertebrate trachea refers to the open respiratory system composed of spiracles, tracheae, and tracheoles that terrestrial arthropods have to transport metabolic gases to and from tissues....

 to suffice for supplying oxygen.

Jawed vertebrate
Gnathostomata
Gnathostomata is the group of vertebrates with jaws. The term derives from Greek γνάθος "jaw" + στόμα "mouth". Gnathostome diversity comprises roughly 60,000 species, which accounts for 99% of all living vertebrates...

s have an adaptive immune system
Adaptive immune system
The adaptive immune system is composed of highly specialized, systemic cells and processes that eliminate or prevent pathogenic growth. Thought to have arisen in the first jawed vertebrates, the adaptive or "specific" immune system is activated by the “non-specific” and evolutionarily older innate...

, based largely on white blood cell
White blood cell
White blood cells, or leukocytes , are cells of the immune system involved in defending the body against both infectious disease and foreign materials. Five different and diverse types of leukocytes exist, but they are all produced and derived from a multipotent cell in the bone marrow known as a...

s. White blood cells help to resist infections and parasites. Platelet
Platelet
Platelets, or thrombocytes , are small,irregularly shaped clear cell fragments , 2–3 µm in diameter, which are derived from fragmentation of precursor megakaryocytes.  The average lifespan of a platelet is normally just 5 to 9 days...

s are important in the clotting
Coagulation
Coagulation is a complex process by which blood forms clots. It is an important part of hemostasis, the cessation of blood loss from a damaged vessel, wherein a damaged blood vessel wall is covered by a platelet and fibrin-containing clot to stop bleeding and begin repair of the damaged vessel...

 of blood. Arthropod
Arthropod
An arthropod is an invertebrate animal having an exoskeleton , a segmented body, and jointed appendages. Arthropods are members of the phylum Arthropoda , and include the insects, arachnids, crustaceans, and others...

s, using hemolymph, have hemocyte
Hemocyte
A hemocyte is a cell that plays a role in the immune system of invertebrates. It is found within the hemolymph.Hemocytes are phagocytes of invertebrates....

s as part of their immune system
Immune system
An immune system is a system of biological structures and processes within an organism that protects against disease by identifying and killing pathogens and tumor cells. It detects a wide variety of agents, from viruses to parasitic worms, and needs to distinguish them from the organism's own...

.

Blood is circulated around the body through blood vessel
Blood vessel
The blood vessels are the part of the circulatory system that transports blood throughout the body. There are three major types of blood vessels: the arteries, which carry the blood away from the heart; the capillaries, which enable the actual exchange of water and chemicals between the blood and...

s by the pumping action of the heart
Heart
The heart is a myogenic muscular organ found in all animals with a circulatory system , that is responsible for pumping blood throughout the blood vessels by repeated, rhythmic contractions...

. In animals with lung
Lung
The lung is the essential respiration organ in many air-breathing animals, including most tetrapods, a few fish and a few snails. In mammals and the more complex life forms, the two lungs are located near the backbone on either side of the heart...

s, arterial
Artery
Arteries are blood vessels that carry blood away from the heart. This blood is normally oxygenated, exceptions made for the pulmonary and umbilical arteries....

 blood carries oxygen from inhaled air to the tissues of the body, and venous
Vein
In the circulatory system, veins are blood vessels that carry blood towards the heart. Most veins carry deoxygenated blood from the tissues back to the heart; exceptions are the pulmonary and umbilical veins, both of which carry oxygenated blood to the heart...

 blood carries carbon dioxide, a waste product of metabolism
Metabolism
Metabolism is the set of chemical reactions that happen in the cells of living organisms to sustain life. These processes allow organisms to grow and reproduce, maintain their structures, and respond to their environments. Metabolism is usually divided into two categories...

 produced by cells
Cell (biology)
The cell is the basic structural and functional unit of all known living organisms. It is the smallest unit of life that is classified as a living thing, and is often called the building block of life. The Alberts text discusses how the "cellular building blocks" move to shape developing embryos....

, from the tissues to the lung
Lung
The lung is the essential respiration organ in many air-breathing animals, including most tetrapods, a few fish and a few snails. In mammals and the more complex life forms, the two lungs are located near the backbone on either side of the heart...

s to be exhaled.

Medical terms related to blood often begin with hemo- or hemato- (also spelled haemo- and haemato-) from the Ancient Greek
Ancient Greek
Ancient Greek is the stage of the Greek language in the periods spanning the times c. 9th–6th centuries BC, , c. 5th–4th centuries BC , and the c. 3rd century BC – 6th century AD of ancient Greece and the ancient world; being predated in the 2nd millennium BC by Mycenaean Greek...

 word (haima) for "blood". In terms of anatomy
Anatomy
Anatomy is a branch of biology and medicine that is the consideration of the structure of living things. It is a general term that includes human anatomy, animal anatomy , and plant anatomy...

 and histology
Histology
Histology is the study of the microscopic anatomy of cells and tissues of plants and animals. It is performed by examining cells and tissues commonly by sectioning and staining; followed by examination under a light microscope or electron microscope...

, blood is considered a specialized form of connective tissue
Connective tissue
"Connective tissue" is a fibrous tissue. It is one of the four traditional classes of tissues . Connective Tissue is found throughout the body.In fact the whole framework of the skeleton and the different specialized connective tissues from the crown of the head to the toes determine the form of...

, given its origin in the bones and the presence of potential molecular fibers in the form of fibrinogen
Fibrinogen
Fibrinogen is a soluble plasma glycoprotein, synthesised by the liver, that is converted by thrombin into fibrin during blood coagulation. This is achieved through processes in the coagulation cascade that activate the zymogen prothrombin to the serine protease thrombin, which is responsible for...

.

Functions



Blood performs many important functions within the body including:
  • Supply of oxygen
    Oxygen
    Oxygen is the element with atomic number 8 and represented by the symbol O. Its name derives from the Greek roots ὀξύς and -γενής , because at the time of naming, it was mistakenly thought that all acids required oxygen in their composition...

     to tissues (bound to hemoglobin
    Hemoglobin
    Hemoglobin is the iron-containing oxygen-transport metalloprotein in the red blood cells of all vertebrates, with the exception of the fish family Channichthyidae, as well as the tissues of some invertebrates...

    , which is carried in red cells)
  • Supply of nutrients such as glucose
    Glucose
    Glucose is a simple sugar and an important carbohydrate in biology. Cells use it as the primary source of energy and a metabolic intermediate...

    , amino acids, and fatty acids (dissolved in the blood or bound to plasma proteins
    Blood proteins
    Blood proteins, also termed serum proteins or plasma proteins, are proteins found in blood plasma. Serum total protein in blood is 7g/dl...

     (e.g., blood lipids))
  • Removal of waste such as carbon dioxide
    Carbon dioxide
    Carbon dioxide is a naturally occurring chemical compound composed of two oxygen atoms covalently bonded to a single carbon atom...

    , urea
    Urea
    Urea or carbamide is an organic compound with the chemical formula CO2. The molecule has two —NH2 groups joined by a carbonyl functional group....

    , and lactic acid
    Lactic acid
    Lactic acid, also known as milk acid, is a chemical compound that plays a role in various biochemical processes and was first isolated in 1780 by the Swedish chemist Carl Wilhelm Scheele. Lactic acid is a carboxylic acid with the chemical formula C3H6O3...

  • Immunological functions, including circulation of white blood cells, and detection of foreign material by antibodies
  • Coagulation
    Coagulation
    Coagulation is a complex process by which blood forms clots. It is an important part of hemostasis, the cessation of blood loss from a damaged vessel, wherein a damaged blood vessel wall is covered by a platelet and fibrin-containing clot to stop bleeding and begin repair of the damaged vessel...

    , which is one part of the body's self-repair mechanism (blood clotting after an open wound in order to stop bleeding)
  • Messenger functions, including the transport of hormones and the signaling of tissue
    Tissue (biology)
    Tissue is a cellular organizational level intermediate between cells and a complete organism. A tissue is an ensemble of cells, not necessarily identical, but from the same origin, that together carry out a specific function. These are called tissues because of their identical functioning...

     damage
  • Regulation of body pH
    PH
    In chemistry, pH is a measure of the acidity or basicity of an aqueous solution. Pure water is said to be neutral, with a pH close to 7.0 at . Solutions with a pH less than 7 are said to be acidic and solutions with a pH greater than 7 are basic or alkaline...

  • Regulation of core body temperature
  • Hydraulic
    Hydraulics
    Hydraulics is a topic in applied science and engineering dealing with the mechanical properties of liquids. Fluid mechanics provides the theoretical foundation for hydraulics, which focuses on the engineering uses of fluid properties. In fluid power, hydraulics is used for the generation, control,...

     functions

Constituents of human blood




Blood accounts for 8% of the human body weight, with an average density of approximately 1060 kg/m3, very close to pure water's density of 1000 kg/m3. The average adult has a blood volume
Blood volume
Blood volume is the volume of blood in the circulatory system of an individual.-Humans:A typical adult has a blood volume of approximately between 4.7 and 5 liters, with females generally having less blood volume than males....

 of roughly 5 liter
Litér
- External links :*...

s (1.3 gal), composed of plasma and several kinds of cells (occasionally called corpuscles); these formed elements of the blood are erythrocytes (red blood cell
Red blood cell
Red blood cells are the most common type of blood cell and the vertebrate organism's principal means of delivering oxygen to the body tissues via the blood flow through the circulatory system...

s, RBCs), leukocytes (white blood cell
White blood cell
White blood cells, or leukocytes , are cells of the immune system involved in defending the body against both infectious disease and foreign materials. Five different and diverse types of leukocytes exist, but they are all produced and derived from a multipotent cell in the bone marrow known as a...

s), and thrombocytes (platelet
Platelet
Platelets, or thrombocytes , are small,irregularly shaped clear cell fragments , 2–3 µm in diameter, which are derived from fragmentation of precursor megakaryocytes.  The average lifespan of a platelet is normally just 5 to 9 days...

s). By volume, the red blood cells constitute about 45% of whole blood, the plasma about 54.3%, and white cells about 0.7%.

Whole blood (plasma and cells) exhibits non-Newtonian
Non-Newtonian fluid
A non-Newtonian fluid is a fluid whose flow properties differ in any way from those of Newtonian fluids. Most commonly the viscosity of non-Newtonian fluids is not independent of shear rate or shear rate history...

, viscoelastic
Blood viscosity
Blood viscosity is a measure of the resistance of blood to flow, which is being deformed by either shear or extensional strain.Blood is a liquid that consists of plasma and particles, such as the red blood cells. The viscosity of blood thus depends on the viscosity of the plasma, in combination...

 fluid dynamics; its flow properties are adapted to flow effectively through tiny capillary blood vessels with less resistance than plasma by itself. In addition, if all human hemoglobin were free in the plasma rather than being contained in RBCs, the circulatory fluid would be too viscous for the cardiovascular system to function effectively.

Cells



One microliter of blood contains:
  • 4.7 to 6.1 million (male), 4.2 to 5.4 million (female) Erythrocytes: Red blood cells contain the blood's hemoglobin
    Hemoglobin
    Hemoglobin is the iron-containing oxygen-transport metalloprotein in the red blood cells of all vertebrates, with the exception of the fish family Channichthyidae, as well as the tissues of some invertebrates...

     and distribute oxygen. Mature red blood cells lack a nucleus
    Cell nucleus
    In cell biology, the nucleus is a membrane-enclosed organelle found in eukaryotic cells. It contains most of the cell's genetic material, organized as multiple long linear DNA molecules in complex with a large variety of proteins, such as histones, to form chromosomes. The genes within these...

     and organelle
    Organelle
    In cell biology, an organelle is a specialized subunit within a cell that has a specific function, and is usually separately enclosed within its own lipid bilayer....

    s in mammals. The red blood cells (together with endothelial vessel cells and other cells) are also marked by glycoprotein
    Glycoprotein
    Glycoproteins are proteins that contain oligosaccharide chains covalently attached to polypeptide side-chains. The carbohydrate is attached to the protein in a cotranslational or posttranslational modification. This process is known as glycosylation. In proteins that have segments extending...

    s that define the different blood types
    Human blood group systems
    The International Society of Blood Transfusion currently recognises 30 major blood group systems . Thus, in addition to the ABO antigens and Rhesus antigens, many other antigens are expressed on the red blood cell surface membrane...

    . The proportion of blood occupied by red blood cells is referred to as the hematocrit
    Hematocrit
    The hematocrit or packed cell volume or erythrocyte volume fraction is the percentage of the concentration of red blood cells in blood. It is normally about 45% for men and 40% for women...

    , and is normally about 45%. The combined surface area of all red blood cells of the human body would be roughly 2,000 times as great as the body's exterior surface.

  • 4,000–11,000 Leukocytes: White blood cells are part of the body's immune system
    Immune system
    An immune system is a system of biological structures and processes within an organism that protects against disease by identifying and killing pathogens and tumor cells. It detects a wide variety of agents, from viruses to parasitic worms, and needs to distinguish them from the organism's own...

    ; they destroy and remove old or aberrant cells and cellular debris, as well as attack infectious agents (pathogens) and foreign substances. The cancer of leukocytes is called leukemia
    Leukemia
    Leukemia or leukaemia is a type of cancer of the blood or bone marrow characterized by an abnormal increase of immature white blood cells called "blasts". Leukemia is a broad term covering a spectrum of diseases...

    .

  • 200,000–500,000 Thrombocytes:: Also called platelet
    Platelet
    Platelets, or thrombocytes , are small,irregularly shaped clear cell fragments , 2–3 µm in diameter, which are derived from fragmentation of precursor megakaryocytes.  The average lifespan of a platelet is normally just 5 to 9 days...

    s, thrombocytes are responsible for blood clotting (coagulation
    Coagulation
    Coagulation is a complex process by which blood forms clots. It is an important part of hemostasis, the cessation of blood loss from a damaged vessel, wherein a damaged blood vessel wall is covered by a platelet and fibrin-containing clot to stop bleeding and begin repair of the damaged vessel...

    ). They change fibrinogen
    Fibrinogen
    Fibrinogen is a soluble plasma glycoprotein, synthesised by the liver, that is converted by thrombin into fibrin during blood coagulation. This is achieved through processes in the coagulation cascade that activate the zymogen prothrombin to the serine protease thrombin, which is responsible for...

     into fibrin
    Fibrin
    Fibrin is a fibrous, non-globular protein involved in the clotting of blood. It is a fibrillar protein that is polymerised to form a "mesh" that forms a hemostatic plug or clot over a wound site....

    . This fibrin creates a mesh onto which red blood cells collect and clot, which then stops more blood from leaving the body and also helps to prevent bacteria from entering the body.

Constitution of normal blood
Parameter Value
Hematocrit
Hematocrit
The hematocrit or packed cell volume or erythrocyte volume fraction is the percentage of the concentration of red blood cells in blood. It is normally about 45% for men and 40% for women...

 

45 ± 7 (38–52%) for males

42 ± 5 (37–47%) for females
pH
PH
In chemistry, pH is a measure of the acidity or basicity of an aqueous solution. Pure water is said to be neutral, with a pH close to 7.0 at . Solutions with a pH less than 7 are said to be acidic and solutions with a pH greater than 7 are basic or alkaline...

 
7.35–7.45
base excess
Base excess
In human physiology, base excess and base deficit refer to an excess or deficit, respectively, in the amount of base present in the blood. The value is usually reported as a concentration in units of mEq/L, with positive numbers indicating an excess of base and negative a deficit...

 
−3 to +3
PO2
Oxygen
Oxygen is the element with atomic number 8 and represented by the symbol O. Its name derives from the Greek roots ὀξύς and -γενής , because at the time of naming, it was mistakenly thought that all acids required oxygen in their composition...

 
10–13 kPa (80–100 mm Hg)
PCO2
Carbon dioxide
Carbon dioxide is a naturally occurring chemical compound composed of two oxygen atoms covalently bonded to a single carbon atom...

 
4.8–5.8 kPa (35–45 mm Hg)
HCO3
Carbonic acid
Carbonic acid is the inorganic compound with the formula H2CO3 . It is also a name sometimes given to solutions of carbon dioxide in water, because such solutions contain small amounts of H2CO3. Carbonic acid forms two kinds of salts, the carbonates and the bicarbonates...

 
21–27 mM
Oxygen saturation
Oxygenated: 98–99%

Deoxygenated: 75%

Plasma


About 55% of whole blood is blood plasma
Blood plasma
Blood plasma is the straw-colored liquid component of blood in which the blood cells in whole blood are normally suspended. It makes up about 55% of the total blood volume. It is the intravascular fluid part of extracellular fluid...

, a fluid that is the blood's liquid medium, which by itself is straw-yellow in color. The blood plasma volume totals of 2.7–3.0 liters (2.8–3.2 quarts) in an average human. It is essentially an aqueous
Water
Water is a chemical substance with the chemical formula H2O. A water molecule contains one oxygen and two hydrogen atoms connected by covalent bonds. Water is a liquid at ambient conditions, but it often co-exists on Earth with its solid state, ice, and gaseous state . Water also exists in a...

 solution containing 92% water, 8% blood plasma protein
Protein
Proteins are biochemical compounds consisting of one or more polypeptides typically folded into a globular or fibrous form, facilitating a biological function. A polypeptide is a single linear polymer chain of amino acids bonded together by peptide bonds between the carboxyl and amino groups of...

s, and trace amounts of other materials. Plasma circulates dissolved nutrients, such as glucose
Glucose
Glucose is a simple sugar and an important carbohydrate in biology. Cells use it as the primary source of energy and a metabolic intermediate...

, amino acids, and fatty acids (dissolved in the blood or bound to plasma proteins), and removes waste products, such as carbon dioxide
Carbon dioxide
Carbon dioxide is a naturally occurring chemical compound composed of two oxygen atoms covalently bonded to a single carbon atom...

, urea
Urea
Urea or carbamide is an organic compound with the chemical formula CO2. The molecule has two —NH2 groups joined by a carbonyl functional group....

, and lactic acid
Lactic acid
Lactic acid, also known as milk acid, is a chemical compound that plays a role in various biochemical processes and was first isolated in 1780 by the Swedish chemist Carl Wilhelm Scheele. Lactic acid is a carboxylic acid with the chemical formula C3H6O3...

.

Other important components include:
  • Serum albumin
    Serum albumin
    Serum albumin, often referred to simply as albumin is a protein that in humans is encoded by the ALB gene.Serum albumin is the most abundant plasma protein in mammals. Albumin is essential for maintaining the osmotic pressure needed for proper distribution of body fluids between intravascular...

  • Blood-clotting factors (to facilitate coagulation
    Coagulation
    Coagulation is a complex process by which blood forms clots. It is an important part of hemostasis, the cessation of blood loss from a damaged vessel, wherein a damaged blood vessel wall is covered by a platelet and fibrin-containing clot to stop bleeding and begin repair of the damaged vessel...

    )
  • Immunoglobulins (antibodies)
  • lipoprotein
    Lipoprotein
    A lipoprotein is a biochemical assembly that contains both proteins and lipids water-bound to the proteins. Many enzymes, transporters, structural proteins, antigens, adhesins, and toxins are lipoproteins...

     particles
  • Various other protein
    Protein
    Proteins are biochemical compounds consisting of one or more polypeptides typically folded into a globular or fibrous form, facilitating a biological function. A polypeptide is a single linear polymer chain of amino acids bonded together by peptide bonds between the carboxyl and amino groups of...

    s
  • Various electrolyte
    Electrolyte
    In chemistry, an electrolyte is any substance containing free ions that make the substance electrically conductive. The most typical electrolyte is an ionic solution, but molten electrolytes and solid electrolytes are also possible....

    s (mainly sodium
    Sodium
    Sodium is a chemical element with the symbol Na and atomic number 11. It is a soft, silvery-white, highly reactive metal and is a member of the alkali metals; its only stable isotope is 23Na. It is an abundant element that exists in numerous minerals, most commonly as sodium chloride...

     and chloride
    Chloride
    The chloride ion is formed when the element chlorine, a halogen, picks up one electron to form an anion Cl−. The salts of hydrochloric acid HCl contain chloride ions and can also be called chlorides. The chloride ion, and its salts such as sodium chloride, are very soluble in water...

    )


The term serum refers to plasma from which the clotting proteins have been removed. Most of the proteins remaining are albumin and immunoglobulins
Antibody
An antibody, also known as an immunoglobulin, is a large Y-shaped protein used by the immune system to identify and neutralize foreign objects such as bacteria and viruses. The antibody recognizes a unique part of the foreign target, termed an antigen...

.

Narrow range of pH values


Blood pH
PH
In chemistry, pH is a measure of the acidity or basicity of an aqueous solution. Pure water is said to be neutral, with a pH close to 7.0 at . Solutions with a pH less than 7 are said to be acidic and solutions with a pH greater than 7 are basic or alkaline...

 is regulated to stay within the narrow range of 7.35 to 7.45, making it slightly alkaline. Blood that has a pH below 7.35 is too acidic, whereas blood pH above 7.45 is too alkaline. Blood pH, partial pressure
Partial pressure
In a mixture of ideal gases, each gas has a partial pressure which is the pressure which the gas would have if it alone occupied the volume. The total pressure of a gas mixture is the sum of the partial pressures of each individual gas in the mixture....

 of oxygen (pO2), partial pressure of carbon dioxide (pCO2), and HCO3
Bicarbonate
In inorganic chemistry, bicarbonate is an intermediate form in the deprotonation of carbonic acid...

 are carefully regulated by a number of homeostatic mechanisms
Homeostasis
Homeostasis is the property of a system that regulates its internal environment and tends to maintain a stable, constant condition of properties like temperature or pH...

, which exert their influence principally through the respiratory system
Respiratory system
The respiratory system is the anatomical system of an organism that introduces respiratory gases to the interior and performs gas exchange. In humans and other mammals, the anatomical features of the respiratory system include airways, lungs, and the respiratory muscles...

 and the urinary system
Urinary system
The urinary system is the organ system that produces, stores, and eliminates urine. In humans it includes two kidneys, two ureters, the bladder and the urethra.-Kidney:...

 in order to control the acid-base balance
Acid-base homeostasis
Acid–base homeostasis is the part of human homeostasis concerning the proper balance between acids and bases, in other words, the pH. The body is very sensitive to its pH level, so strong mechanisms exist to maintain it...

 and respiration. An arterial blood gas
Arterial blood gas
An arterial blood gas is a blood test that is performed using blood from an artery. It involves puncturing an artery with a thin needle and syringe and drawing a small volume of blood. The most common puncture site is the radial artery at the wrist, but sometimes the femoral artery in the groin or...

 will measure these. Plasma also circulates hormone
Hormone
A hormone is a chemical released by a cell or a gland in one part of the body that sends out messages that affect cells in other parts of the organism. Only a small amount of hormone is required to alter cell metabolism. In essence, it is a chemical messenger that transports a signal from one...

s transmitting their messages to various tissues. The list of normal reference ranges for various blood electrolytes is extensive.

Bones are especially affected by blood pH as they tend to be used as a mineral source for pH buffering. Consuming a high ratio of animal protein to vegetable protein is implicated in bone loss in women.

Blood in non-human vertebrates


Human blood is typical of that of mammals, although the precise details concerning cell numbers, size, protein structure
Protein structure
Proteins are an important class of biological macromolecules present in all organisms. Proteins are polymers of amino acids. Classified by their physical size, proteins are nanoparticles . Each protein polymer – also known as a polypeptide – consists of a sequence formed from 20 possible L-α-amino...

, and so on, vary somewhat between species. In non-mammalian vertebrates, however, there are some key differences:
  • Red blood cells of non-mammalian vertebrates are flattened and ovoid in form, and retain their cell nuclei
  • There is considerable variation in the types and proportions of white blood cells; for example, acidophils are generally more common than in humans
  • Platelets are unique to mammals; in other vertebrates, small nucleated, spindle cells are responsible for blood clotting instead

Cardiovascular system



Blood is circulated around the body through blood vessel
Blood vessel
The blood vessels are the part of the circulatory system that transports blood throughout the body. There are three major types of blood vessels: the arteries, which carry the blood away from the heart; the capillaries, which enable the actual exchange of water and chemicals between the blood and...

s by the pumping action of the heart
Heart
The heart is a myogenic muscular organ found in all animals with a circulatory system , that is responsible for pumping blood throughout the blood vessels by repeated, rhythmic contractions...

. In humans, blood is pumped from the strong left ventricle
Left ventricle
The left ventricle is one of four chambers in the human heart. It receives oxygenated blood from the left atrium via the mitral valve, and pumps it into the aorta via the aortic valve.-Shape:...

 of the heart through arteries
Artery
Arteries are blood vessels that carry blood away from the heart. This blood is normally oxygenated, exceptions made for the pulmonary and umbilical arteries....

 to peripheral tissues
Tissue (biology)
Tissue is a cellular organizational level intermediate between cells and a complete organism. A tissue is an ensemble of cells, not necessarily identical, but from the same origin, that together carry out a specific function. These are called tissues because of their identical functioning...

 and returns to the right atrium of the heart through vein
Vein
In the circulatory system, veins are blood vessels that carry blood towards the heart. Most veins carry deoxygenated blood from the tissues back to the heart; exceptions are the pulmonary and umbilical veins, both of which carry oxygenated blood to the heart...

s. It then enters the right ventricle
Ventricle (heart)
In the heart, a ventricle is one of two large chambers that collect and expel blood received from an atrium towards the peripheral beds within the body and lungs. The Atria primes the Pump...

 and is pumped through the pulmonary artery
Pulmonary artery
The pulmonary arteries carry deoxygenated blood from the heart to the lungs. They are the only arteries that carry deoxygenated blood....

 to the lung
Lung
The lung is the essential respiration organ in many air-breathing animals, including most tetrapods, a few fish and a few snails. In mammals and the more complex life forms, the two lungs are located near the backbone on either side of the heart...

s and returns to the left atrium through the pulmonary vein
Pulmonary vein
The pulmonary veins are large blood vessels that carry blood from the lungs to the left atrium of the heart. In humans there are four pulmonary veins, two from each lung...

s. Blood then enters the left ventricle to be circulated again. Arterial blood carries oxygen from inhaled air to all of the cells of the body, and venous blood
Venous blood
Venous blood is deoxygenated blood in the circulatory system. It runs in the systemic veins from the organs to the heart. Deoxygenated blood is then pumped by the heart to lungs via the pulmonary arteries, one of the few arteries in the body that carries deoxygenated blood .Venous blood is...

 carries carbon dioxide, a waste product of metabolism
Metabolism
Metabolism is the set of chemical reactions that happen in the cells of living organisms to sustain life. These processes allow organisms to grow and reproduce, maintain their structures, and respond to their environments. Metabolism is usually divided into two categories...

 by cells
Cell (biology)
The cell is the basic structural and functional unit of all known living organisms. It is the smallest unit of life that is classified as a living thing, and is often called the building block of life. The Alberts text discusses how the "cellular building blocks" move to shape developing embryos....

, to the lungs to be exhaled. However, one exception includes pulmonary arteries, which contain the most deoxygenated blood in the body, while the pulmonary veins contain oxygenated blood.

Additional return flow may be generated by the movement of skeletal muscle
Skeletal muscle
Skeletal muscle is a form of striated muscle tissue existing under control of the somatic nervous system- i.e. it is voluntarily controlled. It is one of three major muscle types, the others being cardiac and smooth muscle...

s, which can compress veins and push blood through the valves in veins toward the right atrium
Right atrium
The right atrium is one of four chambers in the hearts of mammals and archosaurs...

.

The blood circulation was famously described by William Harvey
William Harvey
William Harvey was an English physician who was the first person to describe completely and in detail the systemic circulation and properties of blood being pumped to the body by the heart...

 in 1628.

Production and degradation of blood cells


In vertebrates, the various cells of blood are made in the bone marrow
Bone marrow
Bone marrow is the flexible tissue found in the interior of bones. In humans, bone marrow in large bones produces new blood cells. On average, bone marrow constitutes 4% of the total body mass of humans; in adults weighing 65 kg , bone marrow accounts for approximately 2.6 kg...

 in a process called hematopoiesis, which includes erythropoiesis
Erythropoiesis
Erythropoiesis is the process by which red blood cells are produced. It is stimulated by decreased O2 in circulation, which is detected by the kidneys, which then secrete the hormone erythropoietin...

, the production of red blood cells; and myelopoiesis
Myelopoiesis
Myelopoiesis is the regulated formation of myeloid cells, including eosinophilic granulocytes, basophilic granulocytes, neutrophilic granulocytes, and monocytes...

, the production of white blood cells and platelets. During childhood, almost every human bone produces red blood cells; as adults, red blood cell production is limited to the larger bones: the bodies of the vertebrae, the breastbone (sternum), the ribcage, the pelvic bones, and the bones of the upper arms and legs. In addition, during childhood, the thymus
Thymus
The thymus is a specialized organ of the immune system. The thymus produces and "educates" T-lymphocytes , which are critical cells of the adaptive immune system....

 gland, found in the mediastinum
Mediastinum
The mediastinum is a non-delineated group of structures in the thorax, surrounded by loose connective tissue. It is the central compartment of the thoracic cavity...

, is an important source of lymphocytes.
The proteinaceous component of blood (including clotting proteins) is produced predominantly by the liver
Liver
The liver is a vital organ present in vertebrates and some other animals. It has a wide range of functions, including detoxification, protein synthesis, and production of biochemicals necessary for digestion...

, while hormones are produced by the endocrine glands and the watery fraction is regulated by the hypothalamus
Hypothalamus
The Hypothalamus is a portion of the brain that contains a number of small nuclei with a variety of functions...

 and maintained by the kidney
Kidney
The kidneys, organs with several functions, serve essential regulatory roles in most animals, including vertebrates and some invertebrates. They are essential in the urinary system and also serve homeostatic functions such as the regulation of electrolytes, maintenance of acid–base balance, and...

.

Healthy erythrocytes have a plasma life of about 120 days before they are degraded by the spleen
Spleen
The spleen is an organ found in virtually all vertebrate animals with important roles in regard to red blood cells and the immune system. In humans, it is located in the left upper quadrant of the abdomen. It removes old red blood cells and holds a reserve of blood in case of hemorrhagic shock...

, and the Kupffer cell
Kupffer cell
Kupffer cells, also known as Browicz-Kupffer cells and stellate macrophages, are specialized macrophages located in the liver lining the walls of the sinusoids that form part of the reticuloendothelial system .-History:The cells were first observed by Karl Wilhelm von Kupffer in 1876...

s in the liver. The liver also clears some proteins, lipids, and amino acid
Amino acid
Amino acids are molecules containing an amine group, a carboxylic acid group and a side-chain that varies between different amino acids. The key elements of an amino acid are carbon, hydrogen, oxygen, and nitrogen...

s. The kidney actively secretes waste products into the urine
Urine
Urine is a typically sterile liquid by-product of the body that is secreted by the kidneys through a process called urination and excreted through the urethra. Cellular metabolism generates numerous by-products, many rich in nitrogen, that require elimination from the bloodstream...

.

Oxygen transport



About 98.5% of the oxygen
Oxygen
Oxygen is the element with atomic number 8 and represented by the symbol O. Its name derives from the Greek roots ὀξύς and -γενής , because at the time of naming, it was mistakenly thought that all acids required oxygen in their composition...

 in a sample of arterial blood in a healthy human breathing air at sea-level pressure is chemically combined with the Hgb. About 1.5% is physically dissolved in the other blood liquids and not connected to Hgb. The hemoglobin
Hemoglobin
Hemoglobin is the iron-containing oxygen-transport metalloprotein in the red blood cells of all vertebrates, with the exception of the fish family Channichthyidae, as well as the tissues of some invertebrates...

 molecule is the primary transporter of oxygen in mammals and many other species (for exceptions, see below). Hemoglobin has an oxygen binding capacity of between 1.36 and 1.37 ml O2 per gram Hemoglobin, which increases the total blood oxygen capacity seventyfold, compared to if oxygen solely was carried by its solubility of 0.03 mL O2 per liter blood per mmHg partial pressure
Partial pressure
In a mixture of ideal gases, each gas has a partial pressure which is the pressure which the gas would have if it alone occupied the volume. The total pressure of a gas mixture is the sum of the partial pressures of each individual gas in the mixture....

 of oxygen (approximately 100 mmHg in arteries).

With the exception of pulmonary
Pulmonary artery
The pulmonary arteries carry deoxygenated blood from the heart to the lungs. They are the only arteries that carry deoxygenated blood....

 and umbilical arteries
Umbilical artery
The umbilical artery is a paired artery that is found in the abdominal and pelvic regions. In the fetus, it extends into the umbilical cord.-Umbilical arteries in the fetus:...

 and their corresponding veins, arteries
Artery
Arteries are blood vessels that carry blood away from the heart. This blood is normally oxygenated, exceptions made for the pulmonary and umbilical arteries....

 carry oxygenated blood away from the heart
Heart
The heart is a myogenic muscular organ found in all animals with a circulatory system , that is responsible for pumping blood throughout the blood vessels by repeated, rhythmic contractions...

 and deliver it to the body via arteriole
Arteriole
An arteriole is a small diameter blood vessel in the microcirculation that extends and branches out from an artery and leads to capillaries.Arterioles have muscular walls and are the primary site of vascular resistance...

s and capillaries
Capillary
Capillaries are the smallest of a body's blood vessels and are parts of the microcirculation. They are only 1 cell thick. These microvessels, measuring 5-10 μm in diameter, connect arterioles and venules, and enable the exchange of water, oxygen, carbon dioxide, and many other nutrient and waste...

, where the oxygen is consumed; afterwards, venule
Venule
A venule is a very small blood vessel in the microcirculation that allows deoxygenated blood to return from the capillary beds to the larger blood vessels called veins. Venules range from 8 to 100μm in diameter and are formed when capillaries unite .Venules are blood vessels that drain blood...

s, and vein
Vein
In the circulatory system, veins are blood vessels that carry blood towards the heart. Most veins carry deoxygenated blood from the tissues back to the heart; exceptions are the pulmonary and umbilical veins, both of which carry oxygenated blood to the heart...

s carry deoxygenated blood back to the heart.

Under normal conditions in adult humans at rest; hemoglobin in blood leaving the lungs is about 98–99% saturated with oxygen, achieving an oxygen delivery of between 950 - 1150 mL/min to the body. In a healthy adult at rest, oxygen consumption is approximately 200 - 250 mL/min, and deoxygenated blood returning to the lungs is still approximately 75% (70 to 78%) saturated. Increased oxygen consumption during sustained exercise reduces the oxygen saturation of venous blood, which can reach less than 15% in a trained athlete; although breathing rate and blood flow increase to compensate, oxygen saturation in arterial blood can drop to 95% or less under these conditions. Oxygen saturation this low is considered dangerous in an individual at rest (for instance, during surgery under anesthesia. Sustained hypoxia (oxygenation of less than 90%), is dangerous to health, and severe hypoxia (saturations of less than 30%) may be rapidly fatal.

A fetus
Fetus
A fetus is a developing mammal or other viviparous vertebrate after the embryonic stage and before birth.In humans, the fetal stage of prenatal development starts at the beginning of the 11th week in gestational age, which is the 9th week after fertilization.-Etymology and spelling variations:The...

, receiving oxygen via the placenta
Placenta
The placenta is an organ that connects the developing fetus to the uterine wall to allow nutrient uptake, waste elimination, and gas exchange via the mother's blood supply. "True" placentas are a defining characteristic of eutherian or "placental" mammals, but are also found in some snakes and...

, is exposed to much lower oxygen pressures (about 21% of the level found in an adult's lungs), and, so, fetuses produce another form of hemoglobin with a much higher affinity for oxygen (hemoglobin F
Fetal hemoglobin
Fetal hemoglobin, or foetal haemoglobin, is the main oxygen transport protein in the fetus during the last seven months of development in the uterus and in the newborn until roughly 6 months old...

) in order to function under these conditions.

Carbon dioxide transport


When blood flows through capillaries, carbon dioxide diffuses from the tissues into the blood. Some carbon dioxide is dissolved in the blood. A part of CO2 reacts with hemoglobin and other proteins to form carbamino
Carbamino
Carbamino refers to a compound composed by the addition of carbon dioxide with a free amino group in an amino acid or a protein, such as hemoglobin forming carbaminohemoglobin....

 compounds. The remaining carbon dioxide is converted to bicarbonate
Bicarbonate
In inorganic chemistry, bicarbonate is an intermediate form in the deprotonation of carbonic acid...

 and hydrogen ion
Hydrogen ion
Hydrogen ion is recommended by IUPAC as a general term for all ions of hydrogen and its isotopes.Depending on the charge of the ion, two different classes can be distinguished: positively charged ions and negatively charged ions....

s through the action of RBC carbonic anhydrase
Carbonic anhydrase
The carbonic anhydrases form a family of enzymes that catalyze the rapid interconversion of carbon dioxide and water to bicarbonate and protons , a reversible reaction that occurs rather slowly in the absence of a catalyst...

. Most carbon dioxide is transported through the blood in the form of bicarbonate ions.

Carbon dioxide
Carbon dioxide
Carbon dioxide is a naturally occurring chemical compound composed of two oxygen atoms covalently bonded to a single carbon atom...

 (CO2), the main cellular waste product
Cellular waste product
Cellular waste products are formed as a byproduct of cellular respiration, a series of processes and reactions that generate energy for the cell, in the form of ATP...

 is carried in blood mainly dissolved in plasma
Blood plasma
Blood plasma is the straw-colored liquid component of blood in which the blood cells in whole blood are normally suspended. It makes up about 55% of the total blood volume. It is the intravascular fluid part of extracellular fluid...

, in equilibrium with bicarbonate
Bicarbonate
In inorganic chemistry, bicarbonate is an intermediate form in the deprotonation of carbonic acid...

 (HCO3-) and carbonic acid
Carbonic acid
Carbonic acid is the inorganic compound with the formula H2CO3 . It is also a name sometimes given to solutions of carbon dioxide in water, because such solutions contain small amounts of H2CO3. Carbonic acid forms two kinds of salts, the carbonates and the bicarbonates...

 (H2CO3). 86–90% of CO2 in the body is converted into carbonic acid
Carbonic acid
Carbonic acid is the inorganic compound with the formula H2CO3 . It is also a name sometimes given to solutions of carbon dioxide in water, because such solutions contain small amounts of H2CO3. Carbonic acid forms two kinds of salts, the carbonates and the bicarbonates...

, which can quickly turn into bicarbonate, the chemical equilibrium being important in the pH buffering
Buffering agent
A buffering agent is a weak acid or base used to maintain the acidity of a solution at a chosen value. The function of a buffering agent is to prevent a rapid change in pH when acids or bases are added to the solution. Buffering agents have variable properties—some are more soluble than others;...

 of plasma. Blood pH
PH
In chemistry, pH is a measure of the acidity or basicity of an aqueous solution. Pure water is said to be neutral, with a pH close to 7.0 at . Solutions with a pH less than 7 are said to be acidic and solutions with a pH greater than 7 are basic or alkaline...

 is kept in a narrow range (pH between 7.35 and 7.45).

Transport of hydrogen ions


Some oxyhemoglobin loses oxygen and becomes deoxyhemoglobin. Deoxyhemoglobin binds most of the hydrogen ions as it has a much greater affinity for more hydrogen than does oxyhemoglobin.

Lymphatic system



In mammals, blood is in equilibrium with lymph
Lymph
Lymph is considered a part of the interstitial fluid, the fluid which lies in the interstices of all body tissues. Interstitial fluid becomes lymph when it enters a lymph capillary...

, which is continuously formed in tissues from blood by capillary ultrafiltration. Lymph is collected by a system of small lymphatic vessels and directed to the thoracic duct
Thoracic duct
In human anatomy, the thoracic duct of the lymphatic system is the largest lymphatic vessel in the body. It is also known as the left lymphatic duct, alimentary duct, chyliferous duct, and Van Hoorne's canal....

, which drains into the left subclavian vein
Subclavian vein
The subclavian veins are two large veins, one on either side of the body. Their diameter is approximately that of the smallest finger.-Path:Each subclavian vein is a continuation of the axillary vein and runs from the outer border of the first rib to the medial border of anterior scalene muscle...

 where lymph rejoins the systemic blood circulation.

Thermoregulation


Blood circulation transports heat
Heat
In physics and thermodynamics, heat is energy transferred from one body, region, or thermodynamic system to another due to thermal contact or thermal radiation when the systems are at different temperatures. It is often described as one of the fundamental processes of energy transfer between...

 throughout the body, and adjustments to this flow are an important part of thermoregulation
Thermoregulation
Thermoregulation is the ability of an organism to keep its body temperature within certain boundaries, even when the surrounding temperature is very different...

. Increasing blood flow to the surface (e.g., during warm weather or strenuous exercise) causes warmer skin, resulting in faster heat loss. In contrast, when the external temperature is low, blood flow to the extremities and surface of the skin is reduced and to prevent heat loss and is circulated to the important organs of the body, preferentially.

Hydraulic functions


The restriction of blood flow can also be used in specialized tissues to cause engorgement, resulting in an erection
Erection
Penile erection is a physiological phenomenon where the penis becomes enlarged and firm. Penile erection is the result of a complex interaction of psychological, neural, vascular and endocrine factors, and is usually, though not exclusively, associated with sexual arousal...

 of that tissue; examples are the erectile tissue
Erectile tissue
Erectile tissue is tissue in the body that can become erect, usually by becoming engorged with blood.-Erectile tissue in the clitoris and penis:...

 in the penis
Penis
The penis is a biological feature of male animals including both vertebrates and invertebrates...

 and clitoris
Clitoris
The clitoris is a sexual organ that is present only in female mammals. In humans, the visible button-like portion is located near the anterior junction of the labia minora, above the opening of the urethra and vagina. Unlike the penis, which is homologous to the clitoris, the clitoris does not...

.

Another example of a hydraulic function is the jumping spider
Jumping spider
The jumping spider family contains more than 500 described genera and about 5,000 described species, making it the largest family of spiders with about 13% of all species. Jumping spiders have some of the best vision among invertebrates and use it in courtship, hunting and navigation...

, in which blood forced into the legs under pressure causes them to straighten for a powerful jump, without the need for bulky muscular legs.

Invertebrates


In insect
Insect
Insects are a class of living creatures within the arthropods that have a chitinous exoskeleton, a three-part body , three pairs of jointed legs, compound eyes, and two antennae...

s, the blood (more properly called hemolymph
Hemolymph
Hemolymph, or haemolymph, is a fluid in the circulatory system of some arthropods and is analogous to the fluids and cells making up both blood and interstitial fluid in vertebrates such as birds and mammals...

) is not involved in the transport of oxygen. (Openings called trachea
Invertebrate trachea
The invertebrate trachea refers to the open respiratory system composed of spiracles, tracheae, and tracheoles that terrestrial arthropods have to transport metabolic gases to and from tissues....

e allow oxygen from the air to diffuse directly to the tissues). Insect blood moves nutrients to the tissues and removes waste products in an open system.

Other invertebrates use respiratory proteins to increase the oxygen-carrying capacity. Hemoglobin is the most common respiratory protein found in nature. Hemocyanin
Hemocyanin
Hemocyanins are respiratory proteins in the form of metalloproteins containing two copper atoms that reversibly bind a single oxygen molecule . Oxygenation causes a color change between the colorless Cu deoxygenated form and the blue Cu oxygenated form...

 (blue
Blue
Blue is a colour, the perception of which is evoked by light having a spectrum dominated by energy with a wavelength of roughly 440–490 nm. It is considered one of the additive primary colours. On the HSV Colour Wheel, the complement of blue is yellow; that is, a colour corresponding to an equal...

) contains copper
Copper
Copper is a chemical element with the symbol Cu and atomic number 29. It is a ductile metal with very high thermal and electrical conductivity. Pure copper is soft and malleable; an exposed surface has a reddish-orange tarnish...

 and is found in crustacean
Crustacean
Crustaceans form a very large group of arthropods, usually treated as a subphylum, which includes such familiar animals as crabs, lobsters, crayfish, shrimp, krill and barnacles. The 50,000 described species range in size from Stygotantulus stocki at , to the Japanese spider crab with a leg span...

s and mollusks. It is thought that tunicate
Tunicate
Tunicates, also known as urochordates, are members of the subphylum Tunicata, previously known as Urochordata, a group of underwater saclike filter feeders with incurrent and excurrent siphons that is classified within the phylum Chordata. While most tunicates live on the ocean floor, others such...

s (sea squirts) might use vanabins
Vanabins
Vanabins are a specific group of vanadium-binding metalloproteins. Vanabins are found almost exclusively in the blood cells, or vanadocytes of some ascidians and tunicates . The vanabins extracted from tunicate vanadocytes are often called hemovanadins...

 (protein
Protein
Proteins are biochemical compounds consisting of one or more polypeptides typically folded into a globular or fibrous form, facilitating a biological function. A polypeptide is a single linear polymer chain of amino acids bonded together by peptide bonds between the carboxyl and amino groups of...

s containing vanadium
Vanadium
Vanadium is a chemical element with the symbol V and atomic number 23. It is a hard, silvery gray, ductile and malleable transition metal. The formation of an oxide layer stabilizes the metal against oxidation. The element is found only in chemically combined form in nature...

) for respiratory pigment
Respiratory pigment
A respiratory pigment is a molecule, such as hemoglobin in humans, that increases the oxygen-carrying capacity of the blood. The four most common invertebrate respiratory pigments are hemoglobin, haemocyanin, haemerythrin and chlorocruorin...

 (bright-green, blue, or orange).

In many invertebrates, these oxygen-carrying proteins are freely soluble in the blood; in vertebrates they are contained in specialized red blood cell
Red blood cell
Red blood cells are the most common type of blood cell and the vertebrate organism's principal means of delivering oxygen to the body tissues via the blood flow through the circulatory system...

s, allowing for a higher concentration of respiratory pigments without increasing viscosity
Viscosity
Viscosity is a measure of the resistance of a fluid which is being deformed by either shear or tensile stress. In everyday terms , viscosity is "thickness" or "internal friction". Thus, water is "thin", having a lower viscosity, while honey is "thick", having a higher viscosity...

 or damaging blood filtering organs like the kidneys.

Giant tube worms have unusual hemoglobins that allow them to live in extraordinary environments. These hemoglobins also carry sulfides normally fatal in other animals.

Hemoglobin




Hemoglobin is the principal determinant of the color of blood in vertebrates. Each molecule has four heme groups, and their interaction with various molecules alters the exact color. In vertebrate
Vertebrate
Vertebrates are animals that are members of the subphylum Vertebrata . Vertebrates are the largest group of chordates, with currently about 58,000 species described. Vertebrates include the jawless fishes, bony fishes, sharks and rays, amphibians, reptiles, mammals, and birds...

s and other hemoglobin-using creatures, arterial blood and capillary blood are bright red, as oxygen imparts a strong red color to the heme group. Deoxygenated blood is a darker shade of red; this is present in veins, and can be seen during blood donation
Blood donation
A blood donation occurs when a person voluntarily has blood drawn and used for transfusions or made into medications by a process called fractionation....

 and when venous blood samples are taken. Blood in carbon monoxide poisoning
Carbon monoxide poisoning
Carbon monoxide poisoning occurs after enough inhalation of carbon monoxide . Carbon monoxide is a toxic gas, but, being colorless, odorless, tasteless, and initially non-irritating, it is very difficult for people to detect...

 is bright red, because carbon monoxide
Carbon monoxide
Carbon monoxide , also called carbonous oxide, is a colorless, odorless, and tasteless gas that is slightly lighter than air. It is highly toxic to humans and animals in higher quantities, although it is also produced in normal animal metabolism in low quantities, and is thought to have some normal...

 causes the formation of carboxyhemoglobin
Carboxyhemoglobin
Carboxyhemoglobin is a stable complex of carbon monoxide and hemoglobin that forms in red blood cells when carbon monoxide is inhaled or produced in normal metabolism. Large quantities of it hinder delivery of oxygen to the body...

. In cyanide
Cyanide
A cyanide is a chemical compound that contains the cyano group, -C≡N, which consists of a carbon atom triple-bonded to a nitrogen atom. Cyanides most commonly refer to salts of the anion CN−. Most cyanides are highly toxic....

 poisoning, the body cannot utilize oxygen, so the venous blood remains oxygenated, increasing the redness. While hemoglobin-containing blood is never blue, there are several conditions and diseases wherein the color of the heme groups make the skin appear blue. If the heme is oxidized, methaemoglobin
Methaemoglobin
Methemoglobin is a form of the oxygen-carrying metalloprotein hemoglobin, in which the iron in the heme group is in the Fe3+ state, not the Fe2+ of normal hemoglobin. Methemoglobin cannot release bound oxygen, unlike oxyhemoglobin. It is a bluish chocolate-brown in color...

, which is more brownish and cannot transport oxygen, is formed. In the rare condition sulfhemoglobinemia
Sulfhemoglobinemia
Sulfhemoglobinemia is a rare condition in which there is excess sulfhemoglobin in the blood. The pigment is a greenish derivative of hemoglobin which cannot be converted back to normal, functional hemoglobin...

, arterial hemoglobin is partially oxygenated, and appears dark red with a bluish hue (cyanosis
Cyanosis
Cyanosis is the appearance of a blue or purple coloration of the skin or mucous membranes due to the tissues near the skin surface being low on oxygen. The onset of cyanosis is 2.5 g/dL of deoxyhemoglobin. The bluish color is more readily apparent in those with high hemoglobin counts than it is...

).

Veins in the skin appear blue for a variety of reasons only weakly dependent on the color of the blood. Light scattering in the skin, and the visual processing of color play roles as well.

Skink
Skink
Skinks are lizards belonging to the family Scincidae. Together with several other lizard families, including Lacertidae , they comprise the superfamily or infraorder Scincomorpha...

s in the genus Prasinohaema
Prasinohaema
Prasinohaema is a genus of skinks characterized by having green blood . This condition is caused by an excess buildup of the bile pigment biliverdin...

have green blood due to a buildup of the waste product biliverdin
Biliverdin
Biliverdin is a green tetrapyrrolic bile pigment, and is a product of heme catabolism. It is the pigment responsible for a greenish color sometimes seen in bruises.- Metabolism :...

.

Hemocyanin


The blood of most mollusks – including cephalopods and gastropods – as well as some arthropods, such as horseshoe crab
Horseshoe crab
The Atlantic horseshoe crab, Limulus polyphemus, is a marine chelicerate arthropod. Despite its name, it is more closely related to spiders, ticks, and scorpions than to crabs. Horseshoe crabs are most commonly found in the Gulf of Mexico and along the northern Atlantic coast of North America...

s, is blue, as it contains the copper-containing protein hemocyanin at concentrations of about 50 grams per liter. Hemocyanin is colorless when deoxygenated and dark blue when oxygenated. The blood in the circulation of these creatures, which generally live in cold environments with low oxygen tensions, is grey-white to pale yellow, and it turns dark blue when exposed to the oxygen in the air, as seen when they bleed. This is due to change in color of hemocyanin
Hemocyanin
Hemocyanins are respiratory proteins in the form of metalloproteins containing two copper atoms that reversibly bind a single oxygen molecule . Oxygenation causes a color change between the colorless Cu deoxygenated form and the blue Cu oxygenated form...

 when it is oxidized. Hemocyanin carries oxygen in extracellular fluid
Extracellular fluid
Extracellular fluid usually denotes all body fluid outside of cells. The remainder is called intracellular fluid.In some animals, including mammals, the extracellular fluid can be divided into two major subcompartments, interstitial fluid and blood plasma...

, which is in contrast to the intracellular oxygen transport in mammals by hemoglobin in RBCs.

Hemovanabin


The blood of some species of ascidians
Ascidiacea
Ascidiacea is a class in the Tunicata subphylum of sac-like marine invertebrate filter feeders. Ascidians are characterized by a tough outer "tunic" made of the polysaccharide tunicin, as compared to other tunicates which are less rigid.Ascidians are found all over the world, usually in shallow...

 and tunicate
Tunicate
Tunicates, also known as urochordates, are members of the subphylum Tunicata, previously known as Urochordata, a group of underwater saclike filter feeders with incurrent and excurrent siphons that is classified within the phylum Chordata. While most tunicates live on the ocean floor, others such...

s, also known as sea squirts and sea cucumbers, contains proteins called vanabins
Vanabins
Vanabins are a specific group of vanadium-binding metalloproteins. Vanabins are found almost exclusively in the blood cells, or vanadocytes of some ascidians and tunicates . The vanabins extracted from tunicate vanadocytes are often called hemovanadins...

. These proteins are based on vanadium
Vanadium
Vanadium is a chemical element with the symbol V and atomic number 23. It is a hard, silvery gray, ductile and malleable transition metal. The formation of an oxide layer stabilizes the metal against oxidation. The element is found only in chemically combined form in nature...

, and give the creatures a concentration of vanadium in their bodies 100 times higher than the surrounding sea water. It is not clear whether these vanabins actually carry oxygen. When exposed to oxygen, however, vanabins turn a mustard yellow.

General medical disorders

  • Disorders of volume
    • Injury
      Injury
      -By cause:*Traumatic injury, a body wound or shock produced by sudden physical injury, as from violence or accident*Other injuries from external physical causes, such as radiation injury, burn injury or frostbite*Injury from infection...

       can cause blood loss through bleeding
      Bleeding
      Bleeding, technically known as hemorrhaging or haemorrhaging is the loss of blood or blood escape from the circulatory system...

      . A healthy adult can lose almost 20% of blood volume (1 L) before the first symptom, restlessness, begins, and 40% of volume (2 L) before shock sets in. Thrombocytes are important for blood coagulation
      Coagulation
      Coagulation is a complex process by which blood forms clots. It is an important part of hemostasis, the cessation of blood loss from a damaged vessel, wherein a damaged blood vessel wall is covered by a platelet and fibrin-containing clot to stop bleeding and begin repair of the damaged vessel...

       and the formation of blood clots, which can stop bleeding. Trauma to the internal organs or bones can cause internal bleeding
      Internal bleeding
      Internal bleeding is bleeding occurring inside the body. It can be a serious medical emergency depending on where it occurs , and can potentially cause death and cardiac arrest if proper medical treatment is not received quickly....

      , which can sometimes be severe.
    • Dehydration
      Dehydration
      In physiology and medicine, dehydration is defined as the excessive loss of body fluid. It is literally the removal of water from an object; however, in physiological terms, it entails a deficiency of fluid within an organism...

       can reduce the blood volume by reducing the water content of the blood. This would rarely result in shock (apart from the very severe cases) but may result in orthostatic hypotension
      Orthostatic hypotension
      Orthostatic hypotension, also known as postural hypotension, orthostasis, and colloquially as head rush or dizzy spell, is a form of hypotension in which a person's blood pressure suddenly falls when the person stands up or stretches. The decrease is typically greater than 20/10 mm Hg, and may be...

       and fainting.
  • Disorders of circulation
    • Shock is the ineffective perfusion
      Perfusion
      In physiology, perfusion is the process of nutritive delivery of arterial blood to a capillary bed in the biological tissue. The word is derived from the French verb "perfuser" meaning to "pour over or through."...

       of tissues, and can be caused by a variety of conditions including blood loss, infection
      Infection
      An infection is the colonization of a host organism by parasite species. Infecting parasites seek to use the host's resources to reproduce, often resulting in disease...

      , poor cardiac output
      Cardiac output
      Cardiac output is the volume of blood being pumped by the heart, in particular by a left or right ventricle in the time interval of one minute. CO may be measured in many ways, for example dm3/min...

      .
    • Atherosclerosis
      Atherosclerosis
      Atherosclerosis is a condition in which an artery wall thickens as a result of the accumulation of fatty materials such as cholesterol...

       reduces the flow of blood through arteries, because atheroma lines arteries and narrows them. Atheroma tends to increase with age, and its progression can be compounded by many causes including smoking, high blood pressure
      Hypertension
      Hypertension or high blood pressure is a cardiac chronic medical condition in which the systemic arterial blood pressure is elevated. What that means is that the heart is having to work harder than it should to pump the blood around the body. Blood pressure involves two measurements, systolic and...

      , excess circulating lipids (hyperlipidemia
      Hyperlipidemia
      Hyperlipidemia, hyperlipoproteinemia, or hyperlipidaemia is the condition of abnormally elevated levels of any or all lipids and/or lipoproteins in the blood...

      ), and diabetes mellitus
      Diabetes mellitus
      Diabetes mellitus, often simply referred to as diabetes, is a group of metabolic diseases in which a person has high blood sugar, either because the body does not produce enough insulin, or because cells do not respond to the insulin that is produced...

      .
    • Coagulation can form a thrombosis
      Thrombosis
      Thrombosis is the formation of a blood clot inside a blood vessel, obstructing the flow of blood through the circulatory system. When a blood vessel is injured, the body uses platelets and fibrin to form a blood clot to prevent blood loss...

      , which can obstruct vessels.
    • Problems with blood composition, the pumping action of the heart, or narrowing of blood vessels can have many consequences including hypoxia (lack of oxygen) of the tissues supplied. The term ischemia refers to tissue that is inadequately perfused with blood, and infarction refers to tissue death (necrosis
      Necrosis
      Necrosis is the premature death of cells in living tissue. Necrosis is caused by factors external to the cell or tissue, such as infection, toxins, or trauma. This is in contrast to apoptosis, which is a naturally occurring cause of cellular death...

      ), which can occur when the blood supply has been blocked (or is very inadequate)

Hematological disorders



  • Anemia
    • Insufficient red cell mass (anemia
      Anemia
      Anemia is a decrease in number of red blood cells or less than the normal quantity of hemoglobin in the blood. However, it can include decreased oxygen-binding ability of each hemoglobin molecule due to deformity or lack in numerical development as in some other types of hemoglobin...

      ) can be the result of bleeding, blood disorders like thalassemia
      Thalassemia
      Thalassemia is an inherited autosomal recessive blood disease that originated in the Mediterranean region. In thalassemia the genetic defect, which could be either mutation or deletion, results in reduced rate of synthesis or no synthesis of one of the globin chains that make up hemoglobin...

      , or nutritional deficiencies
      Illnesses related to poor nutrition
      Nutritional diseases are diseases in humans that are directly or indirectly caused by a lack of essential nutrients in the diet. Nutritional diseases are commonly associated with chronic malnutrition. Additionally, conditions such as obesity from overeating can also cause, or contribute to, serious...

      ; and may require blood transfusion
      Blood transfusion
      Blood transfusion is the process of receiving blood products into one's circulation intravenously. Transfusions are used in a variety of medical conditions to replace lost components of the blood...

      . Several countries have blood bank
      Blood bank
      A blood bank is a cache or bank of blood or blood components, gathered as a result of blood donation, stored and preserved for later use in blood transfusion. The term "blood bank" typically refers to a division of a hospital laboratory where the storage of blood product occurs and where proper...

      s to fill the demand for transfusable blood. A person receiving a blood transfusion must have a blood type
      Blood type
      A blood type is a classification of blood based on the presence or absence of inherited antigenic substances on the surface of red blood cells . These antigens may be proteins, carbohydrates, glycoproteins, or glycolipids, depending on the blood group system...

       compatible with that of the donor.
    • Sickle-cell anemia

  • Disorders of cell proliferation
    • Leukemia
      Leukemia
      Leukemia or leukaemia is a type of cancer of the blood or bone marrow characterized by an abnormal increase of immature white blood cells called "blasts". Leukemia is a broad term covering a spectrum of diseases...

       is a group of cancers of the blood-forming tissues.
    • Non-cancerous overproduction of red cells (polycythemia vera
      Polycythemia vera
      Polycythemia vera is a blood disorder in which the bone marrow makes too many red blood cells. It may also result in the overproduction of white blood cells and platelets. Most of the health concerns associated with polycythemia vera are caused by the blood being thicker as a result of the...

      ) or platelets (essential thrombocytosis
      Essential thrombocytosis
      Essential thrombocythemia is a rare chronic blood disorder characterized by the overproduction of platelets by megakaryocytes in the bone marrow in the absence of an alternative cause. In some cases this disorder may be progressive, and rarely may evolve into acute myeloid leukemia or myelofibrosis...

      ) may be premalignant
      Premalignant condition
      A precancerous condition is a disease, syndrome, or finding that, if left untreated, may lead to cancer. It is a generalized state associated with a significantly increased risk of cancer....

      .
    • Myelodysplastic syndrome
      Myelodysplastic syndrome
      The myelodysplastic syndromes are a diverse collection of hematological medical conditions that involve ineffective production of the myeloid class of blood cells....

      s involve ineffective production of one or more cell lines.

  • Disorders of coagulation
    • Hemophilia is a genetic illness
      Genetic disorder
      A genetic disorder is an illness caused by abnormalities in genes or chromosomes, especially a condition that is present from before birth. Most genetic disorders are quite rare and affect one person in every several thousands or millions....

       that causes dysfunction in one of the blood's clotting mechanisms
      Coagulation
      Coagulation is a complex process by which blood forms clots. It is an important part of hemostasis, the cessation of blood loss from a damaged vessel, wherein a damaged blood vessel wall is covered by a platelet and fibrin-containing clot to stop bleeding and begin repair of the damaged vessel...

      . This can allow otherwise inconsequential wounds to be life-threatening, but more commonly results in hemarthrosis
      Hemarthrosis
      Hemarthrosis is a bleeding into joint spaces.-Causes:It usually follows injury but occurs mainly in patients with a predisposition to hemorrhage such as those being treated with warfarin and patients with hemophilia.It can be associated with knee joint arthroplasty.-Treatment:In hemophilia it may...

      , or bleeding into joint spaces, which can be crippling.
    • Ineffective or insufficient platelets can also result in coagulopathy
      Coagulopathy
      Coagulopathy is a condition in which the blood’s ability to clot is impaired. This condition can cause prolonged or excessive bleeding, which may occur spontaneously or following an injury or medical and dental procedures.The normal clotting process depends on the interplay of various proteins in...

       (bleeding disorders).
    • Hypercoagulable state (thrombophilia
      Thrombophilia
      Thrombophilia is an abnormality of blood coagulation that increases the risk of thrombosis . Such abnormalities can be identified in 50% of people who have an episode of thrombosis that was not provoked by other causes...

      ) results from defects in regulation of platelet or clotting factor function, and can cause thrombosis.

  • Infectious disorders of blood
    • Blood is an important vector of infection. HIV
      HIV
      Human immunodeficiency virus is a lentivirus that causes acquired immunodeficiency syndrome , a condition in humans in which progressive failure of the immune system allows life-threatening opportunistic infections and cancers to thrive...

      , the virus
      Virus
      A virus is a small infectious agent that can replicate only inside the living cells of organisms. Viruses infect all types of organisms, from animals and plants to bacteria and archaea...

       that causes AIDS
      AIDS
      Acquired immune deficiency syndrome or acquired immunodeficiency syndrome is a disease of the human immune system caused by the human immunodeficiency virus...

      , is transmitted through contact with blood, semen or other body secretions of an infected person. Hepatitis B and C
      Hepatitis C
      Hepatitis C is an infectious disease primarily affecting the liver, caused by the hepatitis C virus . The infection is often asymptomatic, but chronic infection can lead to scarring of the liver and ultimately to cirrhosis, which is generally apparent after many years...

       are transmitted primarily through blood contact. Owing to blood-borne infections, bloodstained objects are treated as a biohazard
      Biological hazard
      Biological hazards, refer to biological substances that pose a threat to the health of living organisms, primarily that of humans. This can include medical waste or samples of a microorganism, virus or toxin that can impact human health. It can also include substances harmful to animals...

      .
    • Bacterial infection of the blood is bacteremia
      Bacteremia
      Bacteremia is the presence of bacteria in the blood. The blood is normally a sterile environment, so the detection of bacteria in the blood is always abnormal....

       or sepsis
      Sepsis
      Sepsis is a potentially deadly medical condition that is characterized by a whole-body inflammatory state and the presence of a known or suspected infection. The body may develop this inflammatory response by the immune system to microbes in the blood, urine, lungs, skin, or other tissues...

      . Viral Infection is viremia. Malaria
      Malaria
      Malaria is a mosquito-borne infectious disease of humans and other animals caused by eukaryotic protists of the genus Plasmodium. The disease results from the multiplication of Plasmodium parasites within red blood cells, causing symptoms that typically include fever and headache, in severe cases...

       and trypanosomiasis
      Trypanosomiasis
      Trypanosomiasis or trypanosomosis is the name of several diseases in vertebrates caused by parasitic protozoan trypanosomes of the genus Trypanosoma. Approximately 500,000 men, women and children in 36 countries of sub-Saharan Africa suffer from human African trypanosomiasis which is caused by...

       are blood-borne parasitic infections.

Carbon monoxide poisoning



Substances other than oxygen can bind to hemoglobin; in some cases this can cause irreversible damage to the body. Carbon monoxide
Carbon monoxide
Carbon monoxide , also called carbonous oxide, is a colorless, odorless, and tasteless gas that is slightly lighter than air. It is highly toxic to humans and animals in higher quantities, although it is also produced in normal animal metabolism in low quantities, and is thought to have some normal...

, for example, is extremely dangerous when carried to the blood via the lungs by inhalation, because carbon monoxide irreversibly binds to hemoglobin to form carboxyhemoglobin
Carboxyhemoglobin
Carboxyhemoglobin is a stable complex of carbon monoxide and hemoglobin that forms in red blood cells when carbon monoxide is inhaled or produced in normal metabolism. Large quantities of it hinder delivery of oxygen to the body...

, so that less hemoglobin is free to bind oxygen, and fewer oxygen molecules can be transported throughout the blood. This can cause suffocation insidiously. A fire burning in an enclosed room with poor ventilation presents a very dangerous hazard, since it can create a build-up of carbon monoxide in the air. Some carbon monoxide binds to hemoglobin when smoking tobacco
Tobacco
Tobacco is an agricultural product processed from the leaves of plants in the genus Nicotiana. It can be consumed, used as a pesticide and, in the form of nicotine tartrate, used in some medicines...

.

Blood products



Blood for transfusion is obtained from human donors by blood donation
Blood donation
A blood donation occurs when a person voluntarily has blood drawn and used for transfusions or made into medications by a process called fractionation....

 and stored in a blood bank
Blood bank
A blood bank is a cache or bank of blood or blood components, gathered as a result of blood donation, stored and preserved for later use in blood transfusion. The term "blood bank" typically refers to a division of a hospital laboratory where the storage of blood product occurs and where proper...

. There are many different blood type
Blood type
A blood type is a classification of blood based on the presence or absence of inherited antigenic substances on the surface of red blood cells . These antigens may be proteins, carbohydrates, glycoproteins, or glycolipids, depending on the blood group system...

s in humans, the ABO blood group system
ABO blood group system
The ABO blood group system is the most important blood type system in human blood transfusion. The associated anti-A antibodies and anti-B antibodies are usually IgM antibodies, which are usually produced in the first years of life by sensitization to environmental substances such as food,...

, and the Rhesus blood group system
Rhesus blood group system
The Rh blood group system is one of thirty current human blood group systems. Clinically, it is the most important blood group system after ABO. At Present, the Rh blood group system consists of 50 defined blood-group antigens, among which the 5 antigens D, C, c, E, and e are the most important...

 being the most important. Transfusion of blood of an incompatible blood group may cause severe, often fatal, complications, so crossmatching is done to ensure that a compatible blood product is transfused.

Other blood products administered intravenously are platelets, blood plasma, cryoprecipitate, and specific coagulation factor concentrates.

Intravenous administration


Many forms of medication (from antibiotic
Antibiotic
An antibacterial is a compound or substance that kills or slows down the growth of bacteria.The term is often used synonymously with the term antibiotic; today, however, with increased knowledge of the causative agents of various infectious diseases, antibiotic has come to denote a broader range of...

s to chemotherapy
Chemotherapy
Chemotherapy is the treatment of cancer with an antineoplastic drug or with a combination of such drugs into a standardized treatment regimen....

) are administered intravenously, as they are not readily or adequately absorbed by the digestive tract.

After severe acute blood loss, liquid preparations, generically known as plasma expanders, can be given intravenously, either solutions of salts (NaCl, KCl, CaCl2 etc.) at physiological concentrations, or colloidal solutions, such as dextrans, human serum albumin
Human serum albumin
Human serum albumin is the most abundant protein in human blood plasma. It is produced in the liver. Albumin constitutes about half of the blood serum protein...

, or fresh frozen plasma. In these emergency situations, a plasma expander is a more effective life-saving procedure than a blood transfusion, because the metabolism of transfused red blood cells does not restart immediately after a transfusion.

Bloodletting



In modern evidence-based medicine
Evidence-based medicine
Evidence-based medicine or evidence-based practice aims to apply the best available evidence gained from the scientific method to clinical decision making. It seeks to assess the strength of evidence of the risks and benefits of treatments and diagnostic tests...

, bloodletting is used in management of a few rare diseases, including hemochromatosis and polycythemia
Polycythemia
Polycythemia is a disease state in which the proportion of blood volume that is occupied by red blood cells increases...

. However, bloodletting
Bloodletting
Bloodletting is the withdrawal of often little quantities of blood from a patient to cure or prevent illness and disease. Bloodletting was based on an ancient system of medicine in which blood and other bodily fluid were considered to be "humors" the proper balance of which maintained health...

 and leeching
Leeching
*In pre-scientific medicine, leeching was an alternative form of bloodletting in which "bad" blood would be removed via leeches instead of by bleeding...

 were common unvalidated interventions used until the 19th century, as many diseases were incorrectly thought to be due to an excess of blood, according to Hippocratic
Hippocrates
Hippocrates of Cos or Hippokrates of Kos was an ancient Greek physician of the Age of Pericles , and is considered one of the most outstanding figures in the history of medicine...

 medicine.

History


According to the Oxford English Dictionary, the word "blood" dates to the oldest English, circa 1000 AD. The word is derived from Middle English, which is derived from the Old English word blôd, which is akin to the Old High German word bluot, meaning blood. The modern German word is (das) Blut.

Classical Greek medicine


In classical Greek medicine, blood was associated with air, with Springtime, and with a merry and gluttonous (sanguine) personality. It was also believed to be produced exclusively by the liver
Liver
The liver is a vital organ present in vertebrates and some other animals. It has a wide range of functions, including detoxification, protein synthesis, and production of biochemicals necessary for digestion...

.

Hippocratic medicine


In Hippocratic
Hippocrates
Hippocrates of Cos or Hippokrates of Kos was an ancient Greek physician of the Age of Pericles , and is considered one of the most outstanding figures in the history of medicine...

 medicine, blood was considered to be one of the four humors, the others being phlegm
Phlegm
Phlegm is a liquid secreted by the mucous membranes of mammalians. Its definition is limited to the mucus produced by the respiratory system, excluding that from the nasal passages, and particularly that which is expelled by coughing . Phlegm is in essence a water-based gel consisting of...

, yellow bile, and black bile.

Cultural and religious beliefs


Due to its importance to life, blood is associated with a large number of beliefs. One of the most basic is the use of blood as a symbol for family relationships through birth/parentage; to be "related by blood" is to be related by ancestry or descendance, rather than marriage. This bears closely to bloodlines, and sayings such as "blood is thicker than water
Blood is thicker than water
"Blood is thicker than water" is a German proverb , which is also common in English speaking countries. It generally means that the bonds of family and common ancestry are stronger than those bonds between unrelated people .It first appeared in the medieval German beast epic Reinhart Ficks "Blood...

" and "bad blood
Bad Blood
Bad Blood is an English phrase referring to enmity between two people or groups.The phrase may also refer to:-In film and television:* Bad Blood , starring Jack Thompson, about mass murderer Stanley Graham...

", as well as "Blood brother
Blood brother
Blood brother can refer to one of two things: two males related by birth, or two or more men not related by birth who have sworn loyalty to each other. This is usually done in a ceremony, known as a blood oath, where the blood of each man is mingled together...

". Blood is given particular emphasis in the Jewish and Christian religions because Leviticus
Leviticus
The Book of Leviticus is the third book of the Hebrew Bible, and the third of five books of the Torah ....

 17:11 says "the life of a creature is in the blood." This phrase is part of the Levitical law forbidding the drinking of blood or eating meat with the blood still intact instead of being poured off.

Mythic references to blood can sometimes be connected to the life-giving nature of blood, seen in such events as childbirth
Childbirth
Childbirth is the culmination of a human pregnancy or gestation period with the birth of one or more newborn infants from a woman's uterus...

, as contrasted with the blood of injury or death.

Indigenous Australians


In many indigenous Australian Aboriginal peoples'
Indigenous Australians
Indigenous Australians are the original inhabitants of the Australian continent and nearby islands. The Aboriginal Indigenous Australians migrated from the Indian continent around 75,000 to 100,000 years ago....

 traditions, ochre
Ochre
Ochre is the term for both a golden-yellow or light yellow brown color and for a form of earth pigment which produces the color. The pigment can also be used to create a reddish tint known as "red ochre". The more rarely used terms "purple ochre" and "brown ochre" also exist for variant hues...

 (particularly red) and blood, both high in iron
Iron
Iron is a chemical element with the symbol Fe and atomic number 26. It is a metal in the first transition series. It is the most common element forming the planet Earth as a whole, forming much of Earth's outer and inner core. It is the fourth most common element in the Earth's crust...

 content and considered Maban
Maban
Maban or Mabain is a material that is held to be magical in Australian Aboriginal mythology. It is the material from which the shamans and elders of indigenous Australia supposedly derive their magical powers.-References:...

, are applied to the bodies of dancers for ritual. As Lawlor states:

In many Aboriginal rituals and ceremonies, red ochre is rubbed all over the naked bodies of the dancers. In secret, sacred male ceremonies, blood extracted from the veins of the participant's arms is exchanged and rubbed on their bodies. Red ochre is used in similar ways in less-secret ceremonies. Blood is also used to fasten the feathers of birds onto people's bodies. Bird feathers contain a protein that is highly magnetically sensitive.
Lawlor comments that blood employed in this fashion is held by these peoples to attune the dancers to the invisible energetic realm of the Dreamtime. Lawlor then connects these invisible energetic realms and magnetic fields, because iron is magnetic
Magnetism
Magnetism is a property of materials that respond at an atomic or subatomic level to an applied magnetic field. Ferromagnetism is the strongest and most familiar type of magnetism. It is responsible for the behavior of permanent magnets, which produce their own persistent magnetic fields, as well...

.

European paganism


Among the Germanic tribes (such as the Anglo-Saxons
Anglo-Saxons
Anglo-Saxon is a term used by historians to designate the Germanic tribes who invaded and settled the south and east of Great Britain beginning in the early 5th century AD, and the period from their creation of the English nation to the Norman conquest. The Anglo-Saxon Era denotes the period of...

 and the Norsemen
Norsemen
Norsemen is used to refer to the group of people as a whole who spoke what is now called the Old Norse language belonging to the North Germanic branch of Indo-European languages, especially Norwegian, Icelandic, Faroese, Swedish and Danish in their earlier forms.The meaning of Norseman was "people...

), blood was used during their sacrifices; the Blót
Blót
The blót was Norse pagan sacrifice to the Norse gods and the spirits of the land. The sacrifice often took the form of a sacramental meal or feast. Related religious practices were performed by other Germanic peoples, such as the pagan Anglo-Saxons...

s
. The blood was considered to have the power of its originator, and, after the butchering, the blood was sprinkled on the walls, on the statues of the gods, and on the participants themselves. This act of sprinkling blood was called blóedsian in Old English
Old English language
Old English or Anglo-Saxon is an early form of the English language that was spoken and written by the Anglo-Saxons and their descendants in parts of what are now England and southeastern Scotland between at least the mid-5th century and the mid-12th century...

, and the terminology was borrowed by the Roman Catholic Church
Roman Catholic Church
The Catholic Church, also known as the Roman Catholic Church, is the world's largest Christian church, with over a billion members. Led by the Pope, it defines its mission as spreading the gospel of Jesus Christ, administering the sacraments and exercising charity...

 becoming to bless and blessing. The Hittite
Hittite language
Hittite is the extinct language once spoken by the Hittites, a people who created an empire centred on Hattusa in north-central Anatolia...

 word for blood, ishar was a cognate to words for "oath" and "bond", see Ishara
Ishara
Ishara is the Hittite word for "treaty, binding promise", also personified as a goddess of the oath.In Hurrian and Semitic traditions, Išḫara is a love goddess, often identified with Ishtar...

.
The Ancient Greeks
Ancient Greece
Ancient Greece is a civilization belonging to a period of Greek history that lasted from the Archaic period of the 8th to 6th centuries BC to the end of antiquity. Immediately following this period was the beginning of the Early Middle Ages and the Byzantine era. Included in Ancient Greece is the...

 believed that the blood of the gods, ichor
Ichor
In Greek mythology, Ichor is the ethereal golden fluid that is the blood of the gods and/or immortals.-In classical myth:Ichor originates in Greek mythology, where it is the ethereal fluid that is the Greek gods' blood, sometimes said to retain the qualities of the immortal's food and drink,...

, was a substance that was poisonous to mortals.

As a relic of Germanic Law the cruentation
Cruentation
Cruentation , was one of the medieval methods of finding proof against a suspected murderer. The common belief was that the body of the victim would spontaneously bleed in the presence of the murderer.This cruentation was part of the Germanic Laws...

, an ordeal where the corpse of the victim was supposed to start bleeding in the presence of the murderer was used until the early 17th. century.

Judaism


In Judaism
Judaism
Judaism ) is the "religion, philosophy, and way of life" of the Jewish people...

, blood cannot be consumed even in the smallest quantity (Leviticus
Leviticus
The Book of Leviticus is the third book of the Hebrew Bible, and the third of five books of the Torah ....

 3:17 and elsewhere); this is reflected in Jewish dietary
Diet (nutrition)
In nutrition, diet is the sum of food consumed by a person or other organism. Dietary habits are the habitual decisions an individual or culture makes when choosing what foods to eat. With the word diet, it is often implied the use of specific intake of nutrition for health or weight-management...

 laws (Kashrut
Kashrut
Kashrut is the set of Jewish dietary laws. Food in accord with halakha is termed kosher in English, from the Ashkenazi pronunciation of the Hebrew term kashér , meaning "fit" Kashrut (also kashruth or kashrus) is the set of Jewish dietary laws. Food in accord with halakha (Jewish law) is termed...

). Blood is purged from meat
Meat
Meat is animal flesh that is used as food. Most often, this means the skeletal muscle and associated fat and other tissues, but it may also describe other edible tissues such as organs and offal...

 by salting
Salting (food)
Salting is the preservation of food with dry edible salt. It is related to pickling . It is one of the oldest methods of preserving food, and two historically significant salt-cured foods are dried and salted cod and salt-cured meat.Salting is used because most bacteria, fungi and other potentially...

 and soaking in water.

Another ritual involving blood involves the covering of the blood of fowl
Fowl
Fowl is a word for birds in general but usually refers to birds belonging to one of two biological orders, namely the gamefowl or landfowl and the waterfowl...

 and game
Game
A game is structured playing, usually undertaken for enjoyment and sometimes used as an educational tool. Games are distinct from work, which is usually carried out for remuneration, and from art, which is more often an expression of aesthetic or ideological elements...

 after slaughtering (Leviticus
Leviticus
The Book of Leviticus is the third book of the Hebrew Bible, and the third of five books of the Torah ....

 17:13); the reason given by the Torah
Torah
Torah- A scroll containing the first five books of the BibleThe Torah , is name given by Jews to the first five books of the bible—Genesis , Exodus , Leviticus , Numbers and Deuteronomy Torah- A scroll containing the first five books of the BibleThe Torah , is name given by Jews to the first five...

 is: "Because the life of the animal is [in] its blood" (ibid 17:14).

Also if a person of the orthodox Jewish faith suffers a violent death, religious laws order the collection of their blood for burial with them.

Christianity


Some Christian churches, including Roman Catholicism
Roman Catholic Church
The Catholic Church, also known as the Roman Catholic Church, is the world's largest Christian church, with over a billion members. Led by the Pope, it defines its mission as spreading the gospel of Jesus Christ, administering the sacraments and exercising charity...

, Eastern Orthodoxy
Eastern Orthodox Church
The Orthodox Church, officially called the Orthodox Catholic Church and commonly referred to as the Eastern Orthodox Church, is the second largest Christian denomination in the world, with an estimated 300 million adherents mainly in the countries of Belarus, Bulgaria, Cyprus, Georgia, Greece,...

, Oriental Orthodoxy
Oriental Orthodoxy
Oriental Orthodoxy is the faith of those Eastern Christian Churches that recognize only three ecumenical councils — the First Council of Nicaea, the First Council of Constantinople and the First Council of Ephesus. They rejected the dogmatic definitions of the Council of Chalcedon...

, and the Assyrian Church of the East
Assyrian Church of the East
The Assyrian Church of the East, officially the Holy Apostolic Catholic Assyrian Church of the East ʻIttā Qaddishtā w-Shlikhāitā Qattoliqi d-Madnĕkhā d-Āturāyē), is a Syriac Church historically centered in Mesopotamia. It is one of the churches that claim continuity with the historical...

 teach that, when consecrated, the Eucharistic wine actually becomes
Transubstantiation
In Roman Catholic theology, transubstantiation means the change, in the Eucharist, of the substance of wheat bread and grape wine into the substance of the Body and Blood, respectively, of Jesus, while all that is accessible to the senses remains as before.The Eastern Orthodox...

 the blood of Jesus
Jesus
Jesus of Nazareth , commonly referred to as Jesus Christ or simply as Jesus or Christ, is the central figure of Christianity...

 for worshippers to drink. Thus in the consecrated wine, Jesus becomes spiritually and physically present. This teaching is rooted in the Last Supper, as written in the four gospels of the Bible
Bible
The Bible refers to any one of the collections of the primary religious texts of Judaism and Christianity. There is no common version of the Bible, as the individual books , their contents and their order vary among denominations...

, in which Jesus stated to his disciples that the bread that they ate was his body, and the wine was his blood. "This cup is the new testament in my blood, which is shed for you." .

Various forms of Protestantism, especially those of a Wesley
Wesley
Wesley is a name with an Anglo-Norman etymology. The "wes" portion of the name refers to the Western cardinal direction, while the word "lea" refers to a field, pasture, or other clearing in a forest. Thus, the name's origin refers to a "western lea," or a field to the west...

an or Presbyterian lineage, teach that the wine is no more than a symbol of the blood of Christ, who is spiritually but not physically present. Lutheran theology teaches that the body and blood is present together "in, with, and under"
Consubstantiation
Consubstantiation is a theological doctrine that attempts to describe the nature of the Christian Eucharist in concrete metaphysical terms. It holds that during the sacrament, the fundamental "substance" of the body and blood of Christ are present alongside the substance of the bread and wine,...

 the bread and wine of the Eucharistic feast.

Christ's blood is the means for the atonement of sins. Also, ″… the blood of Jesus Christ his [God] Son cleanseth us from all sin.” (1 John 1:7), “… Unto him [God] that loved us, and washed us from our sins in his own blood.” (Revelation 1:5), and “And they overcame him (Satan) by the blood
of the Lamb [Jesus the Christ], and by the word of their testimony …” (Revelation 12:11).

At the Council of Jerusalem
Council of Jerusalem
The Council of Jerusalem is a name applied by historians and theologians to an Early Christian council that was held in Jerusalem and dated to around the year 50. It is considered by Catholics and Orthodox to be a prototype and forerunner of the later Ecumenical Councils...

, the apostles prohibited Christians from consuming blood (except Jesus'), probably because this was a command given to Noah
Noah
Noah was, according to the Hebrew Bible, the tenth and last of the antediluvian Patriarchs. The biblical story of Noah is contained in chapters 6–9 of the book of Genesis, where he saves his family and representatives of all animals from the flood by constructing an ark...

 (Genesis 9:4, see Noahide Law). This command continued to be observed by the Eastern Orthodox.

Islam


Consumption of food containing blood is forbidden by Islamic dietary laws
Islamic dietary laws
Islamic dietary laws provide direction on what is to be considered clean and unclean regarding diet and related issues.-Overview:Islamic jurisprudence specifies which foods are ' and which are '...

. This is derived from the statement in the Qur'an
Qur'an
The Quran , also transliterated Qur'an, Koran, Alcoran, Qur’ān, Coran, Kuran, and al-Qur’ān, is the central religious text of Islam, which Muslims consider the verbatim word of God . It is regarded widely as the finest piece of literature in the Arabic language...

, sura Al-Ma'ida
Al-Ma'ida
Sura Al-Ma'ida is the fifth chapter of the Qur'an, with 120 verses. It is a Madinan sura. The sura's main topics are Isa's and Moses' missions, as well as the claim that their messages are distorted by non-believing Jews and Christians.-Animals:...

 (5:3): "Forbidden to you (for food) are: dead meat, blood, the flesh of swine, and that on which has been invoked the name of other than Allah."

Blood is considered as unclean and in Islam cleanliness is part of the faith, hence there are specific methods to obtain physical and ritual status of cleanliness once bleeding has occurred. Specific rules and prohibitions apply to menstruation
Menstruation
Menstruation is the shedding of the uterine lining . It occurs on a regular basis in sexually reproductive-age females of certain mammal species. This article focuses on human menstruation.-Overview:...

, postnatal bleeding and irregular vaginal bleeding.

Jehovah's Witnesses


Based on their interpretation of scriptures such as Acts 15:28, 29 ("Keep abstaining...from blood."), Jehovah's Witnesses
Jehovah's Witnesses
Jehovah's Witnesses is a millenarian restorationist Christian denomination with nontrinitarian beliefs distinct from mainstream Christianity. The religion reports worldwide membership of over 7 million adherents involved in evangelism, convention attendance of over 12 million, and annual...

 neither consume blood nor accept transfusions of whole blood or its major components: red blood cells, white blood cells, platelets (thrombocytes), and plasma. Members may personally decide whether they will accept medical procedures that involve their own blood or substances that are further fractionated from the four major components.

Chinese and Japanese culture


In Chinese popular culture, it is often said that if a man's nose produces a small flow of blood, he is experiencing sexual desire. This often appears in Chinese-language
China
Chinese civilization may refer to:* China for more general discussion of the country.* Chinese culture* Greater China, the transnational community of ethnic Chinese.* History of China* Sinosphere, the area historically affected by Chinese culture...

 and Hong Kong
Hong Kong
Hong Kong is one of two Special Administrative Regions of the People's Republic of China , the other being Macau. A city-state situated on China's south coast and enclosed by the Pearl River Delta and South China Sea, it is renowned for its expansive skyline and deep natural harbour...

 film
Film
A film, also called a movie or motion picture, is a series of still or moving images. It is produced by recording photographic images with cameras, or by creating images using animation techniques or visual effects...

s as well as in Japan
Japan
Japan is an island nation in East Asia. Located in the Pacific Ocean, it lies to the east of the Sea of Japan, China, North Korea, South Korea and Russia, stretching from the Sea of Okhotsk in the north to the East China Sea and Taiwan in the south...

ese culture parodied in anime
Anime
is the Japanese abbreviated pronunciation of "animation". The definition sometimes changes depending on the context. In English-speaking countries, the term most commonly refers to Japanese animated cartoons....

 and manga
Manga
Manga is the Japanese word for "comics" and consists of comics and print cartoons . In the West, the term "manga" has been appropriated to refer specifically to comics created in Japan, or by Japanese authors, in the Japanese language and conforming to the style developed in Japan in the late 19th...

. Characters, mostly males, will often be shown with a nosebleed if they have just seen someone nude or in little clothing, or if they have had an erotic thought or fantasy; this is based on the idea that a male's blood pressure will spike dramatically when aroused.

Blood libel



Various religious and other groups have been falsely accused of using human blood in rituals; such accusations are known as blood libel
Blood libel
Blood libel is a false accusation or claim that religious minorities, usually Jews, murder children to use their blood in certain aspects of their religious rituals and holidays...

. The most common form of this is blood libel against Jews. Although there is no ritual involving human blood in Jewish law or custom, fabrications of this nature (often involving the murder of children) were widely used during the Middle Ages
Middle Ages
The Middle Ages is a periodization of European history from the 5th century to the 15th century. The Middle Ages follows the fall of the Western Roman Empire in 476 and precedes the Early Modern Era. It is the middle period of a three-period division of Western history: Classic, Medieval and Modern...

 to justify Antisemitic persecution.

Vampire legends



Vampire
Vampire
Vampires are mythological or folkloric beings who subsist by feeding on the life essence of living creatures, regardless of whether they are undead or a living person...

s are mythical creatures that drink blood directly for sustenance, usually with a preference for human blood. Cultures all over the world have myths of this kind; for example the 'Nosferatu' legend, a human who achieves damnation and immortality by drinking the blood of others, originates from Eastern European folklore. Ticks, leeches, female mosquito
Mosquito
Mosquitoes are members of a family of nematocerid flies: the Culicidae . The word Mosquito is from the Spanish and Portuguese for little fly...

es, vampire bat
Vampire bat
Vampire bats are bats whose food source is blood, a dietary trait called hematophagy. There are three bat species that feed solely on blood: the Common Vampire Bat , the Hairy-legged Vampire Bat , and the White-winged Vampire Bat .All three species are native to the Americas, ranging from Mexico to...

s, and an assortment of other natural creatures do consume the blood of other animals, but only bats are associated with vampires. This has no relation to vampire bats, which are new world
New World
The New World is one of the names used for the Western Hemisphere, specifically America and sometimes Oceania . The term originated in the late 15th century, when America had been recently discovered by European explorers, expanding the geographical horizon of the people of the European middle...

 creatures discovered well after the origins of the European myths.

In the applied sciences


Blood residue
Blood residue
In forensic science, blood residue – wet and dry remnants of blood, as well the discoloration of surfaces on which blood has been shed – can help investigators identify weapons, reconstruct a criminal action, and link suspects to the crime...

 can help forensic investigators identify weapons, reconstruct a criminal action, and link suspects to the crime. Through bloodstain pattern analysis
Bloodstain pattern analysis
Bloodstain pattern analysis is one of several specialties in the field of forensic science. The use of bloodstains as evidence is not new; however, the application of modern science has brought it to a higher level...

, forensic information can also be gained from the spatial distribution of bloodstains.

Blood residue analysis is also a technique used in archeology.

In art


Blood is one of the body fluids that has been used in art. In particular, the performances of Viennese Actionist
Viennese Actionism
The term Viennese Actionism describes a short and violent movement in 20th century art that can be regarded as part of the many independent efforts of the 1960s to develop "action art" . Its main participants were Günter Brus, Otto Mühl, Hermann Nitsch and Rudolf Schwarzkogler. As "actionists",...

 Hermann Nitsch
Hermann Nitsch
Hermann Nitsch is an Austrian artist who works in experimental and multimedia modes.Born in Vienna, Nitsch received training in painting during the time he studied at the Wiener Graphische Lehr-und Versuchanstalt. He is called an "actionist" or a performance artist...

, Franko B
Franko B
Franko B is a London-based performance artist. He studied fine art in London at Camberwell College of Arts and Chelsea College of Art . His work was originally based on the bloody and ritualised violation of his own body...

, Lennie Lee
Lennie Lee
Lennie Lee is a South African conceptual artist who lives and works in London.-Life and career:Lennie Lee is a British artist born in Johannesburg, South Africa. He moved to the UK in 1960. He was educated at Dulwich college in London before winning a scholarship to study philosophy at Christ...

, Ron Athey
Ron Athey
Ron Athey is an American performance artist associated with body art and with extreme performance art. He has performed in the U.S. and internationally . Athey's work explores challenging subjects like the relationships between desire, sexuality, and traumatic experience...

, Yang Zhichao
Yang Zhichao
Yang Zhichao Born in 1963 in Gansu province Northern Manchuria, is a performance artist living and working in Beijing....

, and Kira O' Reilly, along with the photography of Andres Serrano
Andres Serrano
Andres Serrano is an American photographer and artist who has become notorious through his photos of corpses and his use of feces and bodily fluids in his work, notably his controversial work "Piss Christ", a red-tinged photograph of a crucifix submerged in a glass container of what was purported...

, have incorporated blood as a prominent visual element. Marc Quinn
Marc Quinn
Marc Quinn is a British artist and part of the group known as Britartists or YBAs . He is known for Alison Lapper Pregnant , Self , and Garden .He is one of the Young British...

 has made sculptures using frozen blood, including a cast of his own head made using his own blood.

In genealogy & family history


The term, blood, is used in genealogical circles
Genealogy
Genealogy is the study of families and the tracing of their lineages and history. Genealogists use oral traditions, historical records, genetic analysis, and other records to obtain information about a family and to demonstrate kinship and pedigrees of its members...

 to refer to one's ancestry
Ancestor
An ancestor is a parent or the parent of an ancestor ....

, origins
Human evolution
Human evolution refers to the evolutionary history of the genus Homo, including the emergence of Homo sapiens as a distinct species and as a unique category of hominids and mammals...

, and ethnic background
Ethnic group
An ethnic group is a group of people whose members identify with each other, through a common heritage, often consisting of a common language, a common culture and/or an ideology that stresses common ancestry or endogamy...

, as in the word, bloodline
Heredity
Heredity is the passing of traits to offspring . This is the process by which an offspring cell or organism acquires or becomes predisposed to the characteristics of its parent cell or organism. Through heredity, variations exhibited by individuals can accumulate and cause some species to evolve...

. Other terms where blood is used in a family history sense are blue-blood, royal blood
Royal Descent
A royal descent is a lineal descent from a monarch. Royal descent is sometimes claimed as a mark of distinction and is seen as a desirable goal of genealogy research. Pretenders and those hoping to improve their social status have often claimed royal descent and, as a result, fabricated lineages...

, mixed-blood
Mixed-blood
The term mixed-blood in the United States is most often employed for individuals of mixed European and Native American ancestry who are not of Hispanic descent . Some of the most prominent in the 19th century were mixed-blood or mixed-race children born of marriages and unions between fur traders...

and blood relative
Kinship terminology
Kinship terminology refers to the various systems used in languages to refer to the persons to whom an individual is related through kinship. Different societies classify kinship relations differently and therefore use different systems of kinship terminology - for example some languages...

.

See also

  • Autotransfusion
    Autotransfusion
    Autotransfusion is a process when a person receives their own blood for a transfusion, instead of banked donor blood. Blood can be pre-donated before a surgery, or can be collected during and after the surgery using a device commonly known as the Cell Saver. The Cell Saver is utilized in surgeries...

  • Blood as food
    Blood as food
    Some cultures consume blood as food, often in combination with meat. The blood may be in the form of blood sausage, as a thickener for sauces, a cured salted form for times of food scarcity, or in a blood soup. This is a product from domesticated animals, obtained at a place and time where the...

    : see black pudding and tiết canh
  • Blood donation
    Blood donation
    A blood donation occurs when a person voluntarily has blood drawn and used for transfusions or made into medications by a process called fractionation....

  • Blood pressure
    Blood pressure
    Blood pressure is the pressure exerted by circulating blood upon the walls of blood vessels, and is one of the principal vital signs. When used without further specification, "blood pressure" usually refers to the arterial pressure of the systemic circulation. During each heartbeat, BP varies...

  • Blood substitutes
    Blood substitutes
    A blood substitute is a substance used to mimic and fulfill some functions of biological blood, usually in the oxygen-carrying sense...

     ("Artificial blood")
  • Blood test
    Blood test
    A blood test is a laboratory analysis performed on a blood sample that is usually extracted from a vein in the arm using a needle, or via fingerprick....

  • Hemophobia
    Blood phobia
    Blood phobia is the extreme and irrational fear of blood. Acute cases of this fear can cause physical reactions that are uncommon in most other fears, specifically vasovagal syncope . Similar reactions can also occur with trypanophobia and traumatophobia...

  • List of human blood components
  • Taboo food and drink: Blood
  • Oct-1-en-3-one
    Oct-1-en-3-one
    Oct-1-en-3-one , also known as 1-octen-3-one, is the odorant that is responsible for the typical metallic smell of metals and blood coming into contact with skin...

     ("Smell" of blood)

External links


  • Blood Groups and Red Cell Antigens. Free online book at NCBI
    National Center for Biotechnology Information
    The National Center for Biotechnology Information is part of the United States National Library of Medicine , a branch of the National Institutes of Health. The NCBI is located in Bethesda, Maryland and was founded in 1988 through legislation sponsored by Senator Claude Pepper...

    Bookshelf ID: NBK2261