Blood vessel

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Blood vessel

The blood vessels are the part of the circulatory system

Circulatory system

The circulatory system is an organ that moves nutrients, gases, and wastes to and from cells to help fight diseases and help stabilize body temperature and pH to maintain homeostasis....
that transport blood

Blood

Blood is a specialized bodily fluid that delivers necessary substances to the body's Cell s ? such as nutrients and oxygen ? and transports waste products away from those same cells....
throughout the body. There are three major types of blood vessels: the arteries

Artery

Arteries are blood vessels that carry blood away from the heart. All arteries, with the exception of the pulmonary and umbilical arteries, carry oxygenated blood....
, which carry the blood away from the heart

Heart

The heart is a muscle organ in all vertebrates responsible for pumping blood through the blood vessels by repeated, rhythmic contractions, or a similar structure in annelids, mollusks, and arthropods....
, the capillaries

Capillary

Capillaries are the smallest of a body's blood vessels, measuring 5-10 micrometre in diameter, which connect arterioles and venules, and enable the interchange of water, oxygen, carbon dioxide, and many other nutrient and waste chemical substances between blood and surrounding tissue s....
, which enable the actual exchange of water and chemicals between the blood and the tissues; and the veins, which carry blood from the capillaries back towards the heart.

arteries and veins have the same basic structure.

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Anatomy

The arteries and veins have the same basic structure. There are three layers, from inside to outside while the capillaries have only one thick cell:

Tunica intima
Tunica intima

The tunica intima is the innermost layer of an artery or vein. It is made up of one layer of endothelial cells and is supported by an internal elastic lamina....
(the thinnest layer): a single layer of simple squamous endothelial cells
Endothelium

The endothelium is the thin layer of cell that line the interior surface of blood vessels, forming an interface between circulating blood in the lumen and the rest of the vessel wall....
glued by a polysaccharide
Polysaccharide

Polysaccharides are relatively complex carbohydrates. They are polymers made up of many monosaccharides joined together by glycosidic bonds. They are therefore very large, often branched, macromolecules....
intercellular matrix, surrounded by a thin layer of subendothelial connective tissue
Connective tissue

Connective tissue is a form of fibrous biological tissue.It is one of the four types of tissue in traditional classifications .Collagen is the main protein of connective tissue in animals and the most abundant protein in mammals, making up about 25% of the total protein content....
interlaced with a number of circularly arranged elastic bands called the internal elastic lamina.
Tunica media
Tunica media

The tunica media is the middle layer of an artery or vein....
(the thickest layer): circularly arranged elastic fiber, connective tissue, polysaccharide substances, the second and third layer are separated by another thick elastic band called external elastic lamina. The tunica media may (especially in arteries) be rich in vascular smooth muscle
Vascular smooth muscle

Vascular smooth muscle refers to the particular type of smooth muscle found within, and composing the majority of the wall of blood vessels....
, which controls the caliber of the vessel.
Tunica adventitia: entirely made of connective tissue. It also contains nerve
Nerve

A nerve is an enclosed, cable-like bundle of Peripheral nervous system axons . A nerve provides a common pathway for the electrochemical nerve impulses that are transmitted along each of the axons....
s that supply the muscular layer, as well as nutrient capillaries (vasa vasorum
Vasa vasorum

The vasa vasorum is a network of small blood vessels that supply large blood vessels.The vasa vasorum is found in large arteries and veins such as the aorta and its branches....
) in the larger blood vessels.

Capillaries

Capillary

Capillaries are the smallest of a body's blood vessels, measuring 5-10 micrometre in diameter, which connect arterioles and venules, and enable the interchange of water, oxygen, carbon dioxide, and many other nutrient and waste chemical substances between blood and surrounding tissue s....
consist of little more than a layer of endothelium and occasional connective tissue.

When blood vessels connect to form a region of diffuse vascular supply it is called an anastomosis

Circulatory anastomosis

Anastomosis occur normally in the body in the circulatory system, serving as backup routes for blood to flow if one link is blocked or otherwise compromised....
(pl. anastomoses). Anastomoses provide critical alternative routes for blood to flow in case of blockages.

Laid end to end, all the blood vessels in an average human body would encircle the earth twice, a distance of approximately 100,000 kilometers.

Types

There are various kinds of blood vessels:

Arteries
Artery

Arteries are blood vessels that carry blood away from the heart. All arteries, with the exception of the pulmonary and umbilical arteries, carry oxygenated blood....

Aorta
Aorta

The aorta is the largest artery in the human body, originating from the left ventricle of the heart and bringing oxygenated blood to all parts of the body in the systemic circulation....
(the largest artery, carries blood out of the heart)
Branches of the aorta, such as the carotid artery, the subclavian artery
Subclavian artery

In human anatomy, the subclavian artery is a major artery of the upper thorax that mainly supplies blood to the head and arms. It is located below the collar bone, hence the name....
, the celiac trunk, the mesenteric arteries, the renal artery
Renal artery

The renal arteries normally arise off the side of the abdominal aorta, immediately below the superior mesenteric artery, and supply the kidneys with blood....
and the iliac artery
Iliac artery

In human anatomy, iliac artery refers to several anatomical structures located in the pelvis:*Common iliac artery - forms at terminus of the aorta....
.

Arteriole
Arteriole

An arteriole is a small diameter blood vessel that extends and branches out from an artery and leads to capillary. Arterioles have thin muscle walls and are the primary site of vascular resistance....
s
Capillaries
Capillary

Capillaries are the smallest of a body's blood vessels, measuring 5-10 micrometre in diameter, which connect arterioles and venules, and enable the interchange of water, oxygen, carbon dioxide, and many other nutrient and waste chemical substances between blood and surrounding tissue s....
(the smallest blood vessels)
Venule
Venule

A venule is a small blood vessel that allows deoxygenated blood to return from the capillary beds to the larger blood vessels called veins.Venules are blood vessels that drain blood directly from the capillary beds....
s
Vein
Vein

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

Large collecting vessels, such as the subclavian vein
Subclavian vein

In human anatomy, the subclavian veins are two large veins, one on either side of the body. Its diameter is approximately that of a man's small finger....
, the jugular vein
Jugular vein

The jugular veins are veins that bring deoxygenated blood from the head back to the heart via the superior vena cava....
, the renal vein
Renal vein

The renal veins are veins that drain the kidney. They connect the kidney to the inferior vena cava.It is usually singular to each kidney, except in the condition "multiple renal veins"....
and the iliac vein
Iliac vein

In human anatomy, iliac vein refers to several anatomical structures located in the pelvis:*External iliac vein - terminates at the common iliac vein, drains the femoral vein....
.
Venae cavae
Venae cavae

The superior and inferior vena cava are collectively called the venae cavae. They are the veins that return deoxygenated blood from the body into the heart....
(the 2 largest veins, carry blood into the heart)

They are roughly grouped as arterial and venous, determined by whether the blood in it is flowing away from (arterial) or toward (venous) the heart

Heart

Oxygen

Oxygen no O2 produced; 2) O2 produced, but absorbed in oceans & seabed rock; 3) O2 starts to gas out of the oceans, but is absorbed by land surfaces and formation of ozone layer; 4-5) O2 sinks filled and the gas accumulates]]...
, although the pulmonary artery

Pulmonary artery

The pulmonary arteries carry blood from heart to the lungs. They are the only artery that carry deoxygenated blood.In the human heart, the pulmonary trunk begins at the base of the right ventricle....
carries "venous blood" and blood flowing in the pulmonary vein

Pulmonary vein

The four pulmonary veins carry oxygen-rich blood from the lungs to the left atrium of the heart. They are the only veins in the post-fetal circulation human body that carry oxygenated blood....
is rich in oxygen. This is because they are carrying the blood to and from the lungs, respectively, to be oxygenated.

Physiology

Blood vessels do not actively engage in the transport of blood (they have no appreciable peristalsis

Peristalsis

Peristalsis is the rhythmic contraction of smooth muscles to propel contents through the digestive tract. The word is derived from New Latin and comes from the Greek language peristaltikos, peristaltic, from peristellein, "to wrap around," and stellein, "to place."...
), but arteries - and veins to a degree - can regulate their inner diameter by contraction of the muscular layer. This changes the blood flow to downstream organs, and is determined by the autonomic nervous system

Autonomic nervous system

The autonomic nervous system is the part of the peripheral nervous system that acts as a control system, maintaining human homeostasis in the body....
. Vasodilation and vasoconstriction are also used antagonistically as methods of thermoregulation

Thermoregulation

Thermoregulation is the ability of an organism to keep its core temperature within certain boundaries, even when the surrounding temperature is very different....
.

Oxygen

Oxygen

Hemoglobin

Hemoglobin is the iron-containing oxygen-transport metalloprotein in the red blood cells of vertebrates, and the tissues of some invertebrates....
in red blood cell

Red blood cell

Red blood cells are the most common type of blood cell and the vertebrate body's principal means of delivering oxygen to the body tissues via the blood....
s) is the most critical nutrient carried by the blood. In all arteries apart from the pulmonary artery, hemoglobin is highly saturated (95-100%) with oxygen. In all veins apart from the pulmonary vein

Pulmonary vein

Hemoglobin

Hemoglobin is the iron-containing oxygen-transport metalloprotein in the red blood cells of vertebrates, and the tissues of some invertebrates....
is desaturated at about 75%. (The values are reversed in the pulmonary circulation.)

The blood pressure in blood vessels is traditionally expressed in millimetres of mercury

Torr

The torr is a non-International System of Units unit of pressure defined as 1/760 of an Atmosphere . It was named after Evangelista Torricelli, an Italian physicist and mathematician who discovered the principle of the barometer in 1644....
(1 mmHg = 133 Pa

Pascal (unit)

The pascal is the SI derived unit of pressure, stress , Young's modulus and tensile strength. It is a measure of force per unit area i.e. equivalent to one newton per square meter or one joule per cubic meter....
). In the arterial system, this is usually around 120 mmHg systolic (high pressure wave due to contraction of the heart) and 80 mmHg diastolic (low pressure wave). In contrast, pressures in the venous system are constant and rarely exceed 10 mmHg.

Vasoconstriction

Vasoconstriction

Vasoconstriction is the narrowing of the blood vessels resulting from contraction of the muscular wall of the vessels, particularly the large arteries, arterioles and veins....
is the constriction of blood vessels (narrowing, becoming smaller in cross-sectional area) by contracting the vascular smooth muscle

Vascular smooth muscle

Vascular smooth muscle refers to the particular type of smooth muscle found within, and composing the majority of the wall of blood vessels....
in the vessel walls. It is regulated by vasoconstrictor

Vasoconstrictor

#REDIRECT vasoconstriction...
s (agents that cause vasoconstriction). These include paracrine factors (e.g. prostaglandin

Prostaglandin

A prostaglandin is any member of a group of lipid compounds that are derived enzymatically from fatty acids and have important functions in the animal body....
s), a number of hormone

Hormone

Hormones are chemicals released by cells that affect cells in other parts of the body. Only a small amount of hormone is required to alter cell metabolism....
s (e.g. vasopressin and angiotensin

Angiotensin

Angiotensin causes blood vessels to constrict, and drives blood pressure up. It is part of the renin-angiotensin-aldosterone system, which is a major target for drugs that lower blood pressure....
) and neurotransmitter

Neurotransmitter

Neurotransmitters are chemistry which relay, amplify and modulate signals between a neuron and another cell . Neurotransmitters are packaged into vesicles that cluster beneath the membrane on the presynaptic side of a synapse, and are released into the synaptic cleft, where they bind to receptors in the membrane on the postsynaptic side of...
s (e.g. epinephrine

Epinephrine

Epinephrine is a hormone and neurotransmitter.Epinephrine increases the "fight or flight" response of the Sympathetic nervous system of the autonomic nervous system....
) from the nervous system.

Vasodilation

Vasodilation

Vasodilation refers to the widening of blood vessels resulting from relaxation of smooth muscle cells within the vessel walls, particularly in the large arteries, smaller arterioles and large veins....
is a similar process mediated by antagonistically acting mediators. The most prominent vasodilator is nitric oxide

Nitric oxide

Nitric oxide or nitrogen monoxide is a chemical compound with chemical formula NitrogenOxygen. This gas is an important signaling molecule in the body of mammals, including humans, and is an extremely important intermediate in the chemical industry....
(termed endothelium-derived relaxing factor

Endothelium-derived relaxing factor

Endothelium-derived relaxing factor is produced and released by the endothelium that results in smooth muscle relaxation. The most well characterized is nitric oxide, and some older sources consider the two terms to be equivalent....
for this reason).

Permeability of the endothelium

Endothelium

The endothelium is the thin layer of cell that line the interior surface of blood vessels, forming an interface between circulating blood in the lumen and the rest of the vessel wall....
is pivotal in the release of nutrients to the tissue. It is also increased in inflammation

Inflammation

Inflammation is the complex biological response of Blood vessel tissues to harmful stimuli, such as pathogens, damaged cells, or irritants. It is a protective attempt by the organism to remove the injurious stimuli as well as initiate the healing process for the tissue....
in response to histamine

Histamine

Histamine is a biogenic amine involved in local immune system as well as regulating physiological function in the gut and acting as a neurotransmitter....
, prostaglandin

Prostaglandin

A prostaglandin is any member of a group of lipid compounds that are derived enzymatically from fatty acids and have important functions in the animal body....
s and interleukin

Interleukin

Interleukins are a group of cytokines that were first seen to be expressed by white blood cells as a means of communication . The name is something of a relic though ; it has since been found that interleukins are produced by a wide variety of body cells....
s, which leads to most of the symptoms of inflammation (swelling, redness and warmth).

Role in disease

Blood vessels play a role in virtually every medical condition. Cancer

Cancer

Cancer is a class of diseases in which a group of cell display uncontrolled growth , invasion , and sometimes metastasis . These three malignant properties of cancers differentiate them from benign tumors, which are self-limited, do not invade or metastasize....
, for example, cannot progress unless the tumor causes angiogenesis

Angiogenesis

Angiogenesis is a physiological process involving the growth of new blood vessels from pre-existing vessels. Though there has been some debate over this, vasculogenesis is the term used for spontaneous blood-vessel formation, and Intussusception is the term for new blood vessel formation by splitting off existing ones....
(formation of new blood vessels) to supply the malignant cells' metabolic demand. Atherosclerosis

Atherosclerosis

Atherosclerosis is a syndrome affecting artery blood vessels. It is a chronic inflammatory response in the walls of arteries, in large part due to the accumulation of macrophage white blood cells and promoted by low density lipoproteins without adequate removal of fats and cholesterol from the macrophages by functional high density lipoprot...
, the formation of lipid

Lipid

Lipids are broadly defined as any fat-soluble , naturally-occurring molecule, such as fats, oils, waxes, cholesterol, sterols, fat-soluble vitamins , monoglycerides, diglycerides, phospholipids, and others....
lumps (atheroma

Atheroma

In pathology, an atheroma is an accumulation and swelling in artery walls that is made up of cells , or cell debris, that contain lipids , calcium and a variable amount of fibrous connective tissue....
s) in the blood vessel wall, is the prime cause of cardiovascular disease

Cardiovascular disease

Cardiovascular disease or cardiovascular diseases refers to the class of diseases that involve the heart or blood vessels . While the term technically refers to any disease that affects the Circulatory system , it is usually used to refer to those related to atherosclerosis ....
, the main cause of death in the Western world.

Blood vessel permeability is increased in inflammation

Inflammation

Physical trauma

Physical trauma refers to a body injury. A trauma patient is someone who has suffered serious and life-threatening physical injury with the potential for secondary complications such as Shock , respiratory failure and death....
or spontaneously, may lead to haemorrhage due to mechanical damage to the vessel endothelium

Endothelium

The endothelium is the thin layer of cell that line the interior surface of blood vessels, forming an interface between circulating blood in the lumen and the rest of the vessel wall....
. In contrast, occlusion of the blood vessel by atherosclerotic plaque, by an embolised

Embolism

In medicine, an embolism occurs when an object migrates from one part of the body and causes a blockage of a blood vessel in another part of the body....
blood clot or a foreign body leads to downstream ischemia

Ischemia

In medicine, ischemia is a restriction in blood supply, generally due to factors in the blood vessels, with resultant damage or dysfunction of tissue....
(insufficient blood supply) and possibly necrosis

Necrosis

Necrosis is the name given to premature death of cell s and living biological tissue. Necrosis is caused by external factors, such as infection, toxins, or trauma....
. Vessel occlusion tends to be a positive feedback system; an occluded vessel creates eddies in the normally laminar flow or plug flow

Plug flow

In fluid mechanics, Plug Flow is a simple model of the velocity profile of a fluid Fluid dynamics in a pipe . In plug flow, the velocity of the fluid is assumed to be constant across any cross-section of the pipe perpendicular to the axis of the pipe....
blood currents. These eddies create abnormal fluid velocity gradients which push blood elements such as cholesterol or chylomicron

Chylomicron

Chylomicrons are large lipoprotein that transport dietary lipids from the intestines to other locations in the body. Chylomicrons are one of the 5 major groups of lipoproteins which enable fats and cholesterol to move within the water based solution of the blood stream....
bodies to the endothelium. These deposit onto the arterial walls which are already partially occluded and build upon the blockage.

Vasculitis

Vasculitis

Vasculitis refers to a heterogeneous group of disorders that are characterized by inflammatory destruction of blood vessels.Both arteries and veins are affected....
is inflammation

Inflammation

Autoimmune disease

Autoimmune diseases arise from an overactive immune response of the body against substances and tissues normally present in the body. In other words, the body attacks its own cells....
or infection

Infection

An infection is the detrimental colonization of a host organism by a foreign species. In an infection, the infecting organism seeks to utilize the host resources to multiply ....
.

Blood vessel

Anatomy

Types

Physiology

Role in disease

See also