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Gastrointestinal Tract

 
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The digestive tract (also known as the alimentary canal) is the system of organ
Organ (anatomy)

In biology, an organ is a biological tissue that performs a specific function or group of functions. Usually there is a main tissue and sporadic tissues....
s within multicellular animals that takes in food
Food

Food is any substance, usually composed of carbohydrates, fats, proteins and water, that can be Eating or Drinking by an animal or human for nutrition or pleasure....
, digests
Digestion

Digestion is the mechanical and chemical breaking down of food into smaller components, to a form that can be Absorption, for instance, by a blood stream....
 it to extract energy and nutrient
Nutrient

A nutrient is a chemical that an organism needs to live and grow or a substance used in an organism's metabolism which must be taken in from its environment....
s, and expels the remaining waste. The major functions of the GI tract are ingestion
Ingestion

Ingestion is the consumption of a substance by an organism. In animals, it normally is accomplished by taking in the substance through the mouth into the gastrointestinal tract, such as through eating or drinking....
, digestion
Digestion

Digestion is the mechanical and chemical breaking down of food into smaller components, to a form that can be Absorption, for instance, by a blood stream....
, absorption, and defecation
Defecation

Defecation is the final act of digestion by which organisms eliminate solid, semisolid or liquid waste material from the digestive tract via the anus....
. The GI tract differs substantially from animal to animal. Some animals have multi-chambered stomachs, while some animals' stomachs contain a single chamber.






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The digestive tract (also known as the alimentary canal) is the system of organ
Organ (anatomy)

In biology, an organ is a biological tissue that performs a specific function or group of functions. Usually there is a main tissue and sporadic tissues....
s within multicellular animals that takes in food
Food

Food is any substance, usually composed of carbohydrates, fats, proteins and water, that can be Eating or Drinking by an animal or human for nutrition or pleasure....
, digests
Digestion

Digestion is the mechanical and chemical breaking down of food into smaller components, to a form that can be Absorption, for instance, by a blood stream....
 it to extract energy and nutrient
Nutrient

A nutrient is a chemical that an organism needs to live and grow or a substance used in an organism's metabolism which must be taken in from its environment....
s, and expels the remaining waste. The major functions of the GI tract are ingestion
Ingestion

Ingestion is the consumption of a substance by an organism. In animals, it normally is accomplished by taking in the substance through the mouth into the gastrointestinal tract, such as through eating or drinking....
, digestion
Digestion

Digestion is the mechanical and chemical breaking down of food into smaller components, to a form that can be Absorption, for instance, by a blood stream....
, absorption, and defecation
Defecation

Defecation is the final act of digestion by which organisms eliminate solid, semisolid or liquid waste material from the digestive tract via the anus....
. The GI tract differs substantially from animal to animal. Some animals have multi-chambered stomachs, while some animals' stomachs contain a single chamber. In a normal human
Human

A human being, also human or man, is a member of a species of bipedalism primates in the family Hominidae . Mitochondrial DNA evidence indicates that modern humans originated in east Africa about 200,000 years ago....
 adult male, the GI tract is approximately 6.5 meters (20 feet) long and consists of the upper and lower GI tracts. The tract may also be divided into foregut
Foregut

The foregut is the anterior part of the alimentary canal, from the mouth to the duodenum at the entrance of the bile duct. At this point it is continuous with the midgut....
, midgut
Midgut

The midgut is the portion of the embryo from which most of the intestines are derived. After it bends around the superior mesenteric artery, it is called the "midgut loop"....
, and hindgut
Hindgut

The hindgut is the posterior part of the alimentary canal. It includes the distal third of the transverse colon and the splenic flexure, the descending colon, sigmoid colon, rectum and upper part of the anal canal....
, reflecting the embryological
Embryology

Embryology is the study of the development of an embryo. An embryo is defined as any organism in a stage before birth or hatching, or in plants, before germination occurs....
 origin of each segment of the tract.

Upper gastrointestinal tract

The upper GI tract consists of the mouth, pharynx
Pharynx

FunctionsThe pharynx is part of the digestive system and respiratory system of many organisms.Because both food and Earth's atmosphere pass through the pharynx, a flap of connective tissue called the epiglottis closes over the trachea when food is swallowed to prevent choking or Pulmonary aspiration....
, esophagus
Esophagus

The esophagus or oesophagus , sometimes known as the gullet, is an Organ in vertebrates which consists of a Muscle tube through which food passes from the pharynx to the stomach....
, and stomach
Stomach

In most mammals, the stomach is a hollow muscular organ of the gastrointestinal tract involved in the second phase of digestion, following mastication....
.
  • The mouth contains the buccal mucosa
    Buccal mucosa

    Buccal mucosa is mucous membrane of the inside of the cheek. It is non-keratinised and is continuous with the mucosae of the soft palate, under surface of tongue and the floor of the mouth....
    , which contains the openings of the salivary gland
    Salivary gland

    The salivary glands in mammals are exocrine glands that produce saliva. They also secrete amylase, an enzyme that breaks down starch into glucose. In other organisms such as Insecta, salivary glands are often used to produce biologically important proteins like silk or glues, and fly salivary glands contain polytene chromosomes that have been usefu...
    s; the tongue
    Tongue

    The tongue is skeletal muscle on the floor of the mouth that manipulates food for chewing . It is the primary organ of taste. Much of the upper surface of the tongue is covered in papillae and taste buds....
    ; and the teeth
    Tooth

    Teeth are small whitish structures found in the jaws of many vertebrates that are used to tear, scrape, and chew food. Some animals, particularly carnivores, also use teeth for hunting or defense....
    .
  • Behind the mouth lies the pharynx
    Pharynx

    FunctionsThe pharynx is part of the digestive system and respiratory system of many organisms.Because both food and Earth's atmosphere pass through the pharynx, a flap of connective tissue called the epiglottis closes over the trachea when food is swallowed to prevent choking or Pulmonary aspiration....
    , which leads to a hollow muscular tube, the esophagus
    Esophagus

    The esophagus or oesophagus , sometimes known as the gullet, is an Organ in vertebrates which consists of a Muscle tube through which food passes from the pharynx to the stomach....
    .
  • 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."...
     takes place, which is the contraction of muscles to propel the food down the esophagus which extends through the chest and pierces the diaphragm
    Diaphragm

    Diaphragm may refer to any of the following:Anatomy* Thoracic diaphragm, a tissue of muscle separating the thorax and abdomen of mammals...
     to reach the stomach..


Lower gastrointestinal tract

The lower GI tract comprises the intestines and anus.
  • Bowel or intestine
    Intestine

    In anatomy, the intestine is the segment of the Gastrointestinal tract extending from the stomach to the anus and, in humans and other mammals, consists of two segments, the small intestine and the large intestine....
    • Small intestine
      Small intestine

      In vertebrates, including mammals, reptiles, birds, and bony fish, the small intestine is the part of the gastrointestinal tract following the stomach, and is where the vast majority of digestion takes place....
      , which has three parts:
      • Duodenum
        Duodenum

        The duodenum is the first section of the small intestine in most higher vertebrates, including mammals, reptiles, and birds. In fish, the divisions of the small intestine are not as clear and the terms anterior intestine or proximal intestine may be used instead of duodenum....
      • Jejunum
        Jejunum

        The jejunum is the middle section of the small intestine in most higher vertebrates, including mammals, reptiles, and birds. In fish, the divisions of the small intestine are not as clear and the terms middle intestine or mid-gut may be used instead of jejunum....
      • Ileum
        Ileum

        The ileum is the final section of the small intestine in most higher vertebrates, including mammals, reptiles, and birds. In fish, the divisions of the small intestine are not as clear and the terms posterior intestine or distal intestine may be used instead of ileum....
    • Large intestine
      Large intestine

      The large intestine is the last part of the digestive system?the final stage of the alimentary canal?in vertebrate animals. Its function is to absorb water from the remaining indigestible food matter, and then to pass this useless feces from the body....
      , which has three parts:
      • Cecum
        Cecum

        The cecum or caecum is a pouch connected to the ascending colon of the large intestine and the ileum. It is separated from the ileum by the ileocecal valve or Bauhin's valve, and is considered to be the beginning of the large intestine....
         (the vermiform appendix
        Vermiform appendix

        In human anatomy, the appendix is a blind ended tube connected to the cecum , from which it develops embryologically. The cecum is a pouch-like structure of the Colon ....
         is attached to the cecum).
      • Colon
        Colon (anatomy)

        The colon is the last portion of the digestive system in most vertebrates; it extracts water and salt from feces before they are defecation from the body....
         (ascending colon
        Ascending colon

        The ascending colon is smaller in caliber than the cecum, with which it is continuous.It passes upward, from its commencement at the cecum, opposite the colic valve, to the under surface of the right lobe of the liver, on the right of the gall-bladderyeo, where it is lodged in a shallow depression, the colic impression; here it bends abrupt...
        , transverse colon
        Transverse colon

        The transverse colon the longest and most movable part of the Colon , passes with a downward convexity from the right hypochondrium region across the abdomen, opposite the confines of the epigastric and umbilical zones, into the left hypochondrium region, where it curves sharply on itself beneath the lower end of the spleen, forming the splen...
        , descending colon
        Descending colon

        The descending colon of humans passes downward through the left hypochondrium and lumbar regions, along the lateral border of the left kidney....
         and sigmoid flexure)
      • Rectum
        Rectum

        The rectum is the final straight portion of the large intestine in some mammals, and the Gastrointestinal tract in others, terminating in the anus....
  • Anus
    Anus

    The anus is an opening at the opposite end of an animal's digestive tract from the mouth. Its function is to expel feces, unwanted semi-solid matter produced during digestion, which, depending on the type of animal, may be one or more of: matter which the animal cannot digest, such as coprolite ; food material after all the nutrients have b...


Accessory organs

Accessory organs to the alimentary canal include the liver, gallbladder, and pancreas. The liver
Liver

The liver is a vital organ present in vertebrates and some other animals; it has a wide range of functions, a few of which are detoxification, protein synthesis, and production of biochemicals necessary for digestion....
 secretes bile
Bile

Bile or gall is a bitter yellow or green fluid secreted by hepatocytes from the liver of most vertebrates. In many species, bile is stored in the gallbladder between meals and upon eating is discharged into the duodenum where the bile aids the process of digestion of lipids....
 into the small intestine via the biliary system, employing the gallbladder
Gallbladder

The gallbladder is a small non-vital Organ which aids in the digestive process and concentrates bile produced in the liver....
 as a reservoir. Apart from storing and concentrating bile, the gallbladder has no other specific function. The pancreas
Pancreas

The pancreas is a gland Organ in the digestive system and endocrine system of vertebrates. It is both an endocrine gland , as well as an exocrine gland, secreting pancreatic juice containing Digestion enzymes that pass to the small intestine....
 secretes an isosmotic fluid containing bicarbonate
Bicarbonate

In inorganic chemistry, bicarbonate is an intermediate form in the deprotonation of carbonic acid. Its chemical formula is HCO3−....
 and several enzymes, including trypsin
Trypsin

Trypsin is a serine protease found in the digestive system, where it breaks down proteins. Trypsin predominantly cleaves peptide chains at the carboxyl side of the amino acids lysine and arginine, except when either is followed by proline....
, chymotrypsin
Chymotrypsin

Chymotrypsin is a digestive enzyme that can perform proteolysis. Chymotrypsin cleaves peptides at the carboxyl side of tyrosine, tryptophan, and phenylalanine because these three amino acids contain aromatic rings, which fit into a 'hydrophobic pocket' in the enzyme....
, lipase
Lipase

A lipase is a water-soluble enzyme that catalyzes the hydrolysis of ester chemical bond in water?insoluble, lipid substrates. Lipases thus comprise a subclass of the esterases....
, and pancreatic amylase
Amylase

Amylase is an enzyme that breaks starch down into sugar. Amylase is present in human saliva, where it begins the chemical process of digestion....
, as well as nucleolytic enzymes (deoxyribonuclease
Deoxyribonuclease

A deoxyribonuclease is any enzyme that catalyzes the hydrolysis of phosphodiester bonds in the DNA backbone. Deoxyribonucleases are thus one type of nuclease....
 and ribonuclease
Ribonuclease

Ribonuclease is a type of nuclease that catalysis the degradation of RNA into smaller components. Ribonucleases can be divided into endoribonucleases and exoribonucleases, and comprise several sub-classes within the EC 2.7 and 3.1 classes of enzymes....
), into the small intestine. Both of these secretory
Secretion

Secretion is the process of, elaborating and releasing Chemical compound from a cell , or a secreted chemical substance or amount of substance. In contrast to excretion, the substance may have a certain function, rather than being a waste product....
 organs aid in digestion
Digestion

Digestion is the mechanical and chemical breaking down of food into smaller components, to a form that can be Absorption, for instance, by a blood stream....
.

Embryology

The gut is an endoderm
Endoderm

Endoderm, is one of the germ layers formed during animal embryogenesis. Cells migrating inward along the archenteron from the inner layer of the gastrula, which develops into the endoderm....
-derived structure. At approximately the 16th day of human development, the embryo begins to fold ventrally (with the embryo's ventral surface becoming concave) in two directions: the sides of the embryo fold in on each other and the head and tail fold towards one another. The result is that a piece of the yolk sac
Yolk sac

The yolk sac is a membranous sac attached to an embryo, providing early nourishment in the form of yolk in bony fishes, sharks, reptiles, birds, and primitive mammals....
, an endoderm
Endoderm

Endoderm, is one of the germ layers formed during animal embryogenesis. Cells migrating inward along the archenteron from the inner layer of the gastrula, which develops into the endoderm....
-lined structure in contact with the ventral aspect of the embryo, begins to be pinched off to become the primitive gut. The yolk sac remains connected to the gut tube via the vitelline duct
Vitelline duct

At the end of the fourth week the yolk-sac presents the appearance of a small pear-shaped vesicle opening into the digestive tube by a long narrow tube, the vitelline duct, also known as the omphalomesenteric duct....
. Usually this structure regresses during development; in cases where it does not, it is known as Meckel's diverticulum
Meckel's diverticulum

A Meckel's diverticulum, a true congenital diverticulum, is a small bulge in the small intestine present at birth. It is a vestigial remnant of the omphalomesenteric duct , and is the most frequent malformation of the gastrointestinal tract....
.

During fetal life, the primitive gut can be divided into three segments: foregut
Foregut

The foregut is the anterior part of the alimentary canal, from the mouth to the duodenum at the entrance of the bile duct. At this point it is continuous with the midgut....
, midgut
Midgut

The midgut is the portion of the embryo from which most of the intestines are derived. After it bends around the superior mesenteric artery, it is called the "midgut loop"....
, and hindgut
Hindgut

The hindgut is the posterior part of the alimentary canal. It includes the distal third of the transverse colon and the splenic flexure, the descending colon, sigmoid colon, rectum and upper part of the anal canal....
. Although these terms are often used in reference to segments of the primitive gut, they are nevertheless used regularly to describe components of the definitive gut as well.

Each segment of the primitive gut gives rise to specific gut and gut-related structures in the adult. Components derived from the gut proper, including the stomach
Stomach

In most mammals, the stomach is a hollow muscular organ of the gastrointestinal tract involved in the second phase of digestion, following mastication....
 and colon
Colon (anatomy)

The colon is the last portion of the digestive system in most vertebrates; it extracts water and salt from feces before they are defecation from the body....
, develop as swellings or dilatations of the primitive gut. In contrast, gut-related derivatives—that is, those structures that derive from the primitive gut but are not part of the gut proper—in general develop as outpouchings of the primitive gut. The blood vessels supplying these structures remain constant throughout development.

part part in adult Gives rise to Arterial supply >- | foregut
Foregut

The foregut is the anterior part of the alimentary canal, from the mouth to the duodenum at the entrance of the bile duct. At this point it is continuous with the midgut....
 		 the pharynx
Pharynx

FunctionsThe pharynx is part of the digestive system and respiratory system of many organisms.Because both food and Earth's atmosphere pass through the pharynx, a flap of connective tissue called the epiglottis closes over the trachea when food is swallowed to prevent choking or Pulmonary aspiration....
, to the upper duodenum
Duodenum

The duodenum is the first section of the small intestine in most higher vertebrates, including mammals, reptiles, and birds. In fish, the divisions of the small intestine are not as clear and the terms anterior intestine or proximal intestine may be used instead of duodenum....
 		 pharynx
Pharynx

FunctionsThe pharynx is part of the digestive system and respiratory system of many organisms.Because both food and Earth's atmosphere pass through the pharynx, a flap of connective tissue called the epiglottis closes over the trachea when food is swallowed to prevent choking or Pulmonary aspiration....
, esophagus
Esophagus

The esophagus or oesophagus , sometimes known as the gullet, is an Organ in vertebrates which consists of a Muscle tube through which food passes from the pharynx to the stomach....
, stomach
Stomach

In most mammals, the stomach is a hollow muscular organ of the gastrointestinal tract involved in the second phase of digestion, following mastication....
, upper duodenum
Duodenum

The duodenum is the first section of the small intestine in most higher vertebrates, including mammals, reptiles, and birds. In fish, the divisions of the small intestine are not as clear and the terms anterior intestine or proximal intestine may be used instead of duodenum....
, respiratory tract
Respiratory tract

In humans the respiratory tract is the part of the anatomy that has to do with the process of Respiration .The respiratory tract is divided into 3 segments:...
 (including the lung
Lung

The lung is the essential respiration organ in 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 in the chest on either side of the heart....
s), liver
Liver

The liver is a vital organ present in vertebrates and some other animals; it has a wide range of functions, a few of which are detoxification, protein synthesis, and production of biochemicals necessary for digestion....
, gallbladder
Gallbladder

The gallbladder is a small non-vital Organ which aids in the digestive process and concentrates bile produced in the liver....
, and pancreas
Pancreas

The pancreas is a gland Organ in the digestive system and endocrine system of vertebrates. It is both an endocrine gland , as well as an exocrine gland, secreting pancreatic juice containing Digestion enzymes that pass to the small intestine....
 		 branches of the celiac artery
Celiac artery

The celiac artery, also known as the celiac trunk and also spelled as coeliac, is the first major branch of the abdominal aorta. Branching from the aorta around the level of the T12 vertebra in humans, it is one of three anterior/ midline branches of the abdominal aorta ....
 |- | midgut
Midgut

The midgut is the portion of the embryo from which most of the intestines are derived. After it bends around the superior mesenteric artery, it is called the "midgut loop"....
 		 lower duodenum, to the first two-thirds of the transverse colon lower duodenum, jejunum
Jejunum

The jejunum is the middle section of the small intestine in most higher vertebrates, including mammals, reptiles, and birds. In fish, the divisions of the small intestine are not as clear and the terms middle intestine or mid-gut may be used instead of jejunum....
, ileum
Ileum

The ileum is the final section of the small intestine in most higher vertebrates, including mammals, reptiles, and birds. In fish, the divisions of the small intestine are not as clear and the terms posterior intestine or distal intestine may be used instead of ileum....
, cecum
Cecum

The cecum or caecum is a pouch connected to the ascending colon of the large intestine and the ileum. It is separated from the ileum by the ileocecal valve or Bauhin's valve, and is considered to be the beginning of the large intestine....
, appendix
Appendix

Appendix, from the Latin word of the same name, may refer to an Index / Bibliography.* In book design, an appendix is a reference section at the end of a book ...
, ascending colon
Ascending colon

The ascending colon is smaller in caliber than the cecum, with which it is continuous.It passes upward, from its commencement at the cecum, opposite the colic valve, to the under surface of the right lobe of the liver, on the right of the gall-bladderyeo, where it is lodged in a shallow depression, the colic impression; here it bends abrupt...
, and first two-thirds of the transverse colon
Transverse colon

The transverse colon the longest and most movable part of the Colon , passes with a downward convexity from the right hypochondrium region across the abdomen, opposite the confines of the epigastric and umbilical zones, into the left hypochondrium region, where it curves sharply on itself beneath the lower end of the spleen, forming the splen...
 		 branches of the superior mesenteric artery
Superior mesenteric artery

See also: Superior Mesenteric Artery SyndromeIn human anatomy, the superior mesenteric artery arises from the anterior surface of the abdominal aorta, just inferior to the origin of the celiac artery, and supplies the intestine from the lower part of the duodenum through two-thirds of the transverse colon, as well as the pancreas....
 |- | hindgut
Hindgut

The hindgut is the posterior part of the alimentary canal. It includes the distal third of the transverse colon and the splenic flexure, the descending colon, sigmoid colon, rectum and upper part of the anal canal....
 		 last third of the transverse colon, to the upper part of the anal canal last third of the transverse colon, descending colon
Descending colon

The descending colon of humans passes downward through the left hypochondrium and lumbar regions, along the lateral border of the left kidney....
, rectum
Rectum

The rectum is the final straight portion of the large intestine in some mammals, and the Gastrointestinal tract in others, terminating in the anus....
, and upper part of the anal canal
Anal canal

The anal canal is the terminal part of the large intestine.It is situated between the rectum and anus, below the level of the pelvic diaphragm....
 		 branches of the inferior mesenteric artery
Inferior mesenteric artery

In human anatomy, the inferior mesenteric artery, often abbreviated as IMA, supplies the large intestine from the Colic flexure to the upper part of the rectum, which includes the descending colon, the sigmoid colon, and part of the rectum....


Physiology


Specialization of organs

Four organs are subject to specialization in the kingdom Animalia.

  • The first organ is the tongue
    Tongue

    The tongue is skeletal muscle on the floor of the mouth that manipulates food for chewing . It is the primary organ of taste. Much of the upper surface of the tongue is covered in papillae and taste buds....
     which is only present in the phylum Chordata.
  • The second organ is the esophagus
    Esophagus

    The esophagus or oesophagus , sometimes known as the gullet, is an Organ in vertebrates which consists of a Muscle tube through which food passes from the pharynx to the stomach....
    . The crop
    Crop (anatomy)

    A crop is a thin-walled expanded portion of the alimentary tract used for the storage of food prior to digestion that is found in many animals, including gastropods, earthworms, leeches, insects, and birds....
     is an enlargement of the esophagus
    Esophagus

    The esophagus or oesophagus , sometimes known as the gullet, is an Organ in vertebrates which consists of a Muscle tube through which food passes from the pharynx to the stomach....
     in birds, insects and other invertebrates that is used to store food temporarily.
  • The third organ is the stomach
    Stomach

    In most mammals, the stomach is a hollow muscular organ of the gastrointestinal tract involved in the second phase of digestion, following mastication....
     . In addition to a glandular stomach (proventriculus), birds have a muscular "stomach" called the ventriculus or "gizzard." The gizzard is used to mechanically grind up food.
  • The fourth organ is the large intestine
    Large intestine

    The large intestine is the last part of the digestive system?the final stage of the alimentary canal?in vertebrate animals. Its function is to absorb water from the remaining indigestible food matter, and then to pass this useless feces from the body....
    . An outpouching of the large intestine called the cecum
    Cecum

    The cecum or caecum is a pouch connected to the ascending colon of the large intestine and the ileum. It is separated from the ileum by the ileocecal valve or Bauhin's valve, and is considered to be the beginning of the large intestine....
     is present in non-ruminant herbivores such as rabbits. It aids in digestion of plant material such as cellulose
    Cellulose

    File:Cellulose Sessel.svgCellulose is an organic compound with the chemical formula , a polysaccharide consisting of a linear chain of several hundred to over ten thousand ? linked D-glucose units....


Pathology

There are a number of diseases and conditions affecting the gastrointestinal system, including:
  • Colorectal cancer
    Colorectal cancer

    Colorectal cancer, also called colon cancer or large bowel cancer, includes cancerous growths in the colon , rectum and Vermiform appendix....
  • Diverticulitis
    Diverticulitis

    Diverticulitis is a common digestive disease particularly found in the colon . Diverticulitis develops from diverticulosis, which involves the formation of pouches on the outside of the colon ....
  • Gastroenteritis
    Gastroenteritis

    Gastroenteritis is inflammation of the gastrointestinal tract, involving both the stomach and the small intestine and resulting in acute diarrhea....
    , also known as "stomach flu";an inflammation of the stomach and intestines
  • Giardiasis
    Giardiasis

    IntroductionGiardiasis in humans is caused by the infection of the small bowel by a single-celled organism called Giardia lamblia. Giardiasis occurs worldwide with a prevalence of 20-30% in developing countries....
  • Inflammatory bowel disease
    Inflammatory bowel disease

    In medicine, inflammatory bowel disease is a group of inflammation conditions of the colon and small intestine. The major types of IBD are Crohn's disease and ulcerative colitis.....
     (Crohn's disease
    Crohn's disease

    Crohn's disease is an inflammatory disease which may affect any part of the gastrointestinal tract from mouth to anus, causing a wide variety of symptoms....
     and ulcerative colitis
    Ulcerative colitis

    Ulcerative colitis is a form of inflammatory bowel disease . Ulcerative colitis is a form of colitis, a disease of the intestine, specifically the large intestine or colon , that includes characteristic Peptic ulcer, or open sores, in the colon....
    )
  • Irritable bowel syndrome
    Irritable bowel syndrome

    Irritable bowel syndrome , also called spastic colon, is a functional bowel disorder characterized by chronic abdominal pain, discomfort, bloating, and alteration of bowel habits in the absence of any organic cause....
  • Pancreatitis
    Pancreatitis

    Pancreatitis is the inflammation of the pancreas. See also acute pancreatitis and chronic pancreatitis for more details....
  • Cholera
    Cholera

    Cholera, sometimes known as Asiatic or epidemic cholera, is an infectious gastroenteritis caused by enterotoxin-producing strains of the bacterium Vibrio cholerae....
  • Peptic ulcer disease


Immune function

The gastrointestinal tract is also a prominent part of the immune system
Immune system

An immune system is a collection of biological processes within an organism that protects against disease by identifying and killing pathogens and tumour cells....
. The low pH
PH

pH is a measure of the Acid or Base of a solution. It is defined as the cologarithm of the Activity of dissolved hydrogen ions . Hydrogen ion activity coefficients cannot be measured experimentally, so they are based on theoretical calculations....
 (ranging from 1 to 4) of the stomach is fatal for many microorganism
Microorganism

A microorganism or microbe is an organism that is microscopic . The study of microorganisms is called microbiology, a subject that began with Anton van Leeuwenhoek's discovery of microorganisms in 1675, using a microscope of his own design....
s that enter it. Similarly, mucus
Mucus

In vertebrates, mucus is a slippery secretion produced by, and covering, mucous membranes. It is a viscous colloid containing antiseptic enzymes and immunoglobulins that serves to protect Epithelium in the respiratory,...
 (containing IgA
IGA

IGA may stand for:Acronyms* Islamic Golden Age, also known as the Islamic Renaissance* Irish Games Association* International Gamers Award...
 antibodies) neutralizes many of these microorganisms. Other factors in the GI tract help with immune function as well, including enzyme
Enzyme

Enzymes are biomolecules that catalysis chemical reactions. Almost all enzymes are proteins. In enzymatic reactions, the molecules at the beginning of the process are called Substrate , and the enzyme converts them into different molecules, the products....
s in the saliva
Saliva

Saliva is the watery and usually frothy substance produced in the mouths of humans and most other animals. Saliva is produced in and secreted from the salivary glands....
 and bile
Bile

Bile or gall is a bitter yellow or green fluid secreted by hepatocytes from the liver of most vertebrates. In many species, bile is stored in the gallbladder between meals and upon eating is discharged into the duodenum where the bile aids the process of digestion of lipids....
. Enzyme
Enzyme

Enzymes are biomolecules that catalysis chemical reactions. Almost all enzymes are proteins. In enzymatic reactions, the molecules at the beginning of the process are called Substrate , and the enzyme converts them into different molecules, the products....
s such as Cyp3A4, along with the antiporter activities, are also instrumental in the intestine's role of detoxification of antigen
Antigen

An antigen is a substance that prompts the generation of antibodies and can cause an immune response. The word originated from the notion that they can stimulate antibody generation....
s and xenobiotics, such as drugs, involved in first pass metabolism. Health-enhancing intestinal bacteria serve to prevent the overgrowth of potentially harmful bacteria
Bacteria

The Bacteria are a large group of unicellular microorganisms. Typically a few micrometres in length, bacteria have a wide range of shapes, ranging from spheres to rods and spirals....
 in the gut. Microorganisms are also kept at bay by an extensive immune system comprising the gut-associated lymphoid tissue
Gut-associated lymphoid tissue

The digestive tract's immune system is often referred to as gut-associated lymphoid tissue and works to protect the body from invasion....
 (GALT).

Histology

The gastrointestinal tract has a uniform general histology with some differences which reflect the specialization in functional anatomy. The GI tract can be divided into 4 concentric layers:
  • Mucosa
  • Submucosa
    Submucosa

    In the gastrointestinal tract, the submucosa is the layer of dense irregular connective tissue that supports the mucosa, as well as joins the mucosa to the bulk of underlying smooth muscle ....
  • Muscularis externa (the external muscle layer)
  • Adventitia
    Adventitia

    Adventitia is the outermost connective tissue covering of any Organ , Blood vessel, or other structure. It is also called the tunica adventitia....
     or serosa


Mucosa

The mucosa is the innermost layer of the gastrointestinal tract that is surrounding the lumen
Lumen (anatomy)

A lumen in biology is the inside space of a tubular structure, such as an artery or intestine. By extension, a lumen can also be the inside space of a cellular component or structure, such as the endoplasmic reticulum....
, or space within the tube. This layer comes in direct contact with the food (or bolus), and is responsible for absorption and secretion
Secretion

Secretion is the process of, elaborating and releasing Chemical compound from a cell , or a secreted chemical substance or amount of substance. In contrast to excretion, the substance may have a certain function, rather than being a waste product....
, important processes in digestion.

The mucosa can be divided into:
  • Epithelium
    Epithelium

    In biology and medicine, epithelium is a Biological tissue composed of cell s that line the cavities and surfaces of structures throughout the body....
  • Lamina propria
    Lamina propria

    The lamina propria is a constituent of the moist linings known as mucous membranes or mucosa, which line various tubes in the body .The lamina propria is a thin layer of areolar connective tissue which lies beneath the epithelium and together with the epithelium constitutes the mucosa....
  • Muscularis mucosae
    Muscularis mucosae

    The lamina muscularis mucosae is the thin layer of smooth muscle found in most parts of the gastrointestinal tract, located outside the Lamina propria and separating it from the submucosa....


The mucosae are highly specialized in each organ of the gastrointestinal tract, facing a low pH in the stomach, absorbing a multitude of different substances in the small intestine, and also absorbing specific quantities of water in the large intestine. Reflecting the varying needs of these organs, the structure of the mucosa can consist of invaginations of secretory glands (e.g., gastric pits), or it can be folded in order to increase surface area (examples include villi and plicae circulares).

Submucosa

The submucosa consists of a dense irregular layer of connective tissue with large blood vessels, lymphatics and nerves branching into the mucosa and muscularis. It contains Meissner's plexus, an enteric nervous plexus
Enteric nervous system

The enteric nervous system is a subdivision of the Peripheral Nervous System, that directly controls the gastrointestinal system.It is derived from neural crest....
, situated on the inner surface of the muscularis externa.

Muscularis externa

The muscularis externa consists of an inner circular layer and a longitudinal
Longitudinal

The term, longitudinal means "along the major axis" as opposed to latitudinal which means "along the width", transverse, or across.*In automotive engineering, a longitudinal engine is an engine in which the crankshaft is oriented along the long axis of the vehicle, front to back....
 outer muscular layer. The circular muscle layer prevents the food from going backwards and the longitudinal layer shortens the tract. The coordinated contractions of these layers is called 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."...
 and propels the bolus, or balled-up food, through the GI tract. Between the two muscle layers are the myenteric or Auerbach's plexus
Auerbach's plexus

Part of the enteric nervous system, Auerbach's plexus exists between the longitudinal and circular layers of muscularis externa in the gastrointestinal tract and provides motor innervation to both layers and secretomotor innervation to the mucosa, having both parasympathetic and Sympathetic nervous system input, whereas Meissner's plexus has...
.

Adventitia

The adventitia
Adventitia

Adventitia is the outermost connective tissue covering of any Organ , Blood vessel, or other structure. It is also called the tunica adventitia....
 consists of several layers of epithelia. When the adventitia is facing the mesentery
Mesentery

In anatomy, the mesentery is the double layer of peritoneum that suspends the jejunum and ileum from the posterior wall of the abdomen. Its meaning, however, is frequently extended to include double layers of peritoneum connecting various components of the abdominal cavity....
 or peritoneal fold, the adventitia is covered by a mesothelium supported by a thin 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....
 layer, together forming a serosa, or serous membrane.

Uses of animal gut by humans

  • The stomachs of calves have commonly been used as a source of rennet
    Rennet

    Rennet is a natural complex of enzymes produced in any mammalian stomach to digest the mother's milk, and is often used in the production of cheese....
     for making cheese
    Cheese

    Cheese is a food consisting of proteins and fat from milk, usually the milk of cattle, Water Buffalo, goats, or sheep's milk. It is produced by Coagulation of the milk protein casein....
    .
  • The use of animal gut strings
    Strings (music)

    A string is the Vibrating string that is the source of vibration in string instruments, such as the guitar, harp, piano, and members of the violin family....
     by musicians can be traced back to the third dynasty of Egypt
    Third dynasty of Egypt

    Third Dynasty The Third Dynasty of ancient Egypt is the first dynasty of the Old Kingdom. Other dynasties of the Old Kingdom include the Fourth dynasty of Egypt, Fifth dynasty of Egypt and Sixth dynasty of Egypt....
    . In the recent past, strings were made out of lamb
    Domestic sheep

    Domestic sheep are quadrupedal, ruminant mammals typically kept as livestock. Like all ruminants, sheep are members of the order Artiodactyla, the even-toed ungulates....
     gut. With the advent of the modern era, musicians have tended to use strings made of silk
    Silk

    Silk is a natural protein fiber, some forms of which can be weaving into textiles. The best-known type of silk is obtained from Pupa#Cocoons made by the larvae of the mulberry silkworm Bombyx mori reared in captivity ....
    , or synthetic materials such as nylon
    Nylon

    Nylon is a generic designation for a family of synthetic polymers known generically as polyamides and first produced on February 28, 1935 by Wallace Carothers at DuPont....
     or steel
    Steel

    Steel is an alloy consisting mostly of iron, with a carbon content between 0.2% and 2.14% by weight , depending on grade. Carbon is the most cost-effective alloying material for iron, but various other alloying elements are used such as manganese, chromium, vanadium, and tungsten....
    . Some instrumentalists, however, still use gut strings in order to evoke the older tone quality. Although such strings were commonly referred to as "catgut
    Catgut

    Catgut is a type of cord usually prepared from the intestines of sheep or goat. It can also be made using the intestines of a Hog , horse, mule, pig or donkey....
    " strings, cat
    Cat

    The cat , also known as the Domestication cat or house cat to distinguish it from other Felinae and Felidae, is a small predationy carnivore species of crepuscular mammal that is valued by humans for its companionship and its ability to hunt vermin, snakes, scorpions, and other unwanted household pests....
    s were never used as a source for gut strings.
  • Sheep gut was the original source for natural gut string used in racquet
    Racquet

    A racquet is a sports implement consisting of a handled frame with an open hoop across which a network of cord is stretched tightly. It is used for striking a ball in such games as squash , tennis, racquetball, and badminton....
    s, such as for tennis
    Tennis

    Tennis is a sport played between two players or between two teams of two players each . Each player uses a strung racquet to strike a hollow rubber Tennis ball covered with felt over a net into the opponent's tennis court....
    . Today, synthetic strings are much more common, but the best strings are now made out of cow gut.
  • Gut cord has also been used to produce strings for the snares which provide the snare drum
    Snare drum

    The snare drum is a drum with strands of snares made of curled metal wire, metal cable, plastic cable, or catgut cords stretched across the a drumhead, typically the bottom....
    's characteristic buzzing timbre. While the snare drum currently almost always uses metal wire rather than gut cord, the North Africa
    North Africa

    North Africa or Northern Africa is the northernmost region of the African continent, separated by the Sahara from Sub-Saharan Africa.Geopolitically, the United Nations subregion of Northern Africa includes the following seven countries or territories:...
    n bendir
    Bendir

    The bendir is a frame drum used as a traditional instrument throughout North Africa, more specifically in Morocco. Unlike the tambourine, it has no jingles but most often has a snare stretched across its head, which when the drum is struck with the fingers or palm gives the tone a buzzing quality....
     frame drum still uses gut for this purpose.
  • "Natural" sausage hulls (or casings
    Casing (sausage)

    Casing or sausage casing is the material that contains and encloses the filling of a sausage. Casings are typically divided into two categories, natural and artificial....
    ) are made of animal gut, especially hog, beef, and lamb.
  • Animal gut was used to make the cord lines in longcase clock
    Longcase clock

    A longcase clock, also tall-case clock, grandfather clock or floor clock, is a freestanding, weight-driven, pendulum clock with the pendulum held inside the tower, or waist of the case....
    s and for fusee movements in bracket clock
    Bracket clock

    A bracket clock is a style of antique portable table clock made in the 17th and 18th centuries. The term originated with small weight driven clocks that had to be mounted on a bracket on the wall to allow room for their hanging weights....
    s, but may be replaced by metal wire.
  • The oldest known condom
    Condom

    A condom is a device most commonly used during sexual intercourse. It is put on a man's erect penis and physically blocks ejaculated semen from entering the body of a sexual partner....
    s, from 1640 AD, were made from animal intestine.


See also

  • Dysbiosis
    Dysbiosis

    Dysbiosis is the condition of having microbial imbalances on or within the body. Dysbiosis is most prominent in the digestive tract or on the skin, but can also occur on any exposed surface or mucous membrane such as the vagina, lungs, nose, sinuses, ears, nails, or eyes....
  • Gastrointestinal hormone
    Gastrointestinal hormone

    The gastrointestinal hormones constitute a group of hormones secreted by enteroendocrine cells in the stomach, pancreas, and small intestine that control various functions of the digestive organs....
  • Dorland's Illustrated Medical Dictionary
  • Major systems of the human body


External links

  • at Colorado State University
    Colorado State University

    Colorado State University is a public institution of higher learning located in Fort Collins, Colorado, Colorado in the United States. Colorado State University is the state's Morrill Act university and the flagship campus university of the Colorado State University System....
  • at