Intestine - Citizendia

In anatomy, the intestine is the segment of the alimentary canal extending from the stomach to the anus and, in humans and other mammals, consists of two segments, the small intestine and the large intestine. Anatomy (from the Greek anatomia, from ana separate apart from and temnein, to cut up cut open is a branch of Biology that is the consideration In Human anatomy, the stomach is a J-shaped hollow muscular organ of the Gastrointestinal tract involved in the second phase of Digestion, following The anus is an opening at the opposite end of an Animal 's Digestive tract from the Mouth. In Biology the small Intestine is the part of the Gastrointestinal tract (gut between the Stomach and the Large intestine, and comprises 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 In humans, the small intestine is further subdivided into the duodenum, jejunum and ileum while the large intestine is subdivided into the cecum and colon. In Anatomy of the Digestive system, the duodenum is a hollow jointed tube about 25-30 cm (10-12 in long connecting the Stomach to the Jejunum In Anatomy of the Digestive system, the jejunum is the central of the three divisions of the Small intestine and lies between the Duodenum and In Anatomy of the Digestive system, the ileum is the final section of the Small 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 The colon is a storage tube for solid wastes The main function of the colon appears to be extraction of Water and salts from Feces. ^[1]

1 Structure and Function
- 1.1 Gross anatomy
- 1.2 Microanatomy
2 Diseases
3 Disorders
4 References
5 See also

Structure and Function

Intestine for sausage making

The structure and function can be described both as gross anatomy and at a microscopic level.

Gross anatomy

The intestinal tract can be broadly divided into two different parts, the small and large intestine. Grayish-purple in color and about 35 mm (1. 5 inches) in diameter, the small intestine is the first and longest, measuring 6 meters (20 feet) long average in an adult man. Shorter and relatively stockier, the large intestine is a dark reddish color, measuring roughly 1. 5 meters (5 feet) long on average.

Microanatomy

The lumen is the cavity where digested material passes through and from where nutrients are absorbed. A lumen (Lat lūmen, an opening or light (pl lumina is the inside space or lining of a tubular structure such as an artery or intestine Both intestines share a general structure with the whole gut, and are composed of several layers. Going from inside the lumen radially outwards, one passes the mucosa (glandular epithelium and muscularis mucosa), (submucosa, (muscularis (externa and serosa. ))

Along the whole length of the gut in the glandular epithelium are goblet cells. The intestinal epithelium is the Epithelium that covers the small and Large intestine. Goblet cells are Glandular simple columnar epithelial cells whose sole function is to secrete Mucus. These secrete mucus which lubricates the passage of food along and protects it from digestive enzymes. In vertebrates mucus is a slippery secretion produced by and covering Mucous membranes It is a viscous Colloid containing Antiseptic enzymes (such as Villi are vaginations of the mucosa and increase the overall surface area of the intestine while also containing a lacteal, which is connected to the lymph system and aids in the removal of lipids and tissue fluid from the blood supply. Intestinal villi (singular villus) are tiny finger-like projections that come out from the wall of the Small intestine and have additional extensions called microvilli The mucous membranes (or mucosae; singular mucosa) are linings of mostly endodermal origin covered in Epithelium, which are involved in A lacteal is a lymphatic capillary that absorbs dietary fats in the villi of the Small intestine. The lymphatic system in Vertebrates is a network of conduits that carry a clear fluid called Lymph. Lipids are broadly defined as any fat- Soluble ( lipophilic) naturally-occurring Molecule, such as fats oils waxes cholesterol sterols fat-soluble Microvilli are present on the epithelium of a villus and further increase the surface area over which absorption can take place.

The next layer is the muscularis mucosa which is a layer of smooth muscle that aids in the action of continued peristalsis along the gut. The submucosa contains nerves, blood vessels and elastic fibre with collagen that stretches with increased capacity but maintains the shape of the intestine.

Surrounding this is the muscularis externa which comprises longitudinal and smooth muscle that again helps with continued peristalsis and the movement of digested material out of and along the gut.

Lastly there is the serosa which is made up of loose connective tissue and coated in mucus so as to prevent friction damage from the intestine rubbing against other tissue. In Anatomy, a serous membrane (or serosa) is a smooth membrane consisting of a thin layer of cells which excrete Serous fluid Holding all this in place are the mesenteries which suspend the intestine in the abdominal cavity and stop it being disturbed when a person is physically active. In Anatomy, the mesentery is the double layer of Peritoneum that suspends the Jejunum and Ileum from the posterior wall of the Abdomen

The large intestine hosts several kinds of bacteria that deal with molecules the human body is not able to breakdown itself. The Bacteria ( singular: bacterium) are a large group of unicellular Microorganisms Typically a few Micrometres in length bacteria have This is an example of symbiosis. This article is about the biological phenomenon for other uses see Symbiosis (disambiguation The term symbiosis (from the Greek These bacteria also account for the production of gases inside our intestine (this gas is released as flatulence when eliminated through the anus). Flatulence is the production of a mixture of gases in the digestive tract of Mammals that are byproducts of the digestion process However the large intestine is mainly concerned with the absorption of water from digested material (which is regulated by the hypothalamus), the reabsorption of sodium, as well as any nutrients that may have escaped primary digestion in the ileum. The hypothalamus links the Nervous system to the Endocrine system via the Pituitary gland (hypophysis Sodium (ˈsoʊdiəm is an element which has the symbol Na( Latin natrium, from Arabic natrun) atomic number 11 atomic mass 22

Diseases

Gastroenteritis is inflammation of the intestines and is the most common disease of the intestines. Gastroenteritis (also known as gastro, gastric flu, and stomach flu, although unrelated to Influenza) is Inflammation of the
Ileus is a blockage of the intestines. Ileus is a disruption of the normal propulsive gastrointestinal motor activity from non-mechanical mechanisms
Ileitis is an inflammation of the ileum. Ileitis is an inflammation of the Ileum, a portion of the Small intestine. In Anatomy of the Digestive system, the ileum is the final section of the Small intestine.
Colitis is an inflammation of the large intestine. Colitis is a chronic digestive disease characterized by Inflammation of the colon. 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
Appendicitis is inflammation of the vermiform appendix located at the caecum. Appendicitis (or epityphlitis) is a condition characterized by Inflammation of the appendix. In Human anatomy, the appendix (or vermiform appendix; also cecal (or caecal appendix; also vermix) is a blind ended tube connected to the This is a potentially fatal disease if left untreated; most cases of appendicitis require surgical intervention.
Coeliac disease is a common form of malabsorption, affecting up to 1% of people of northern European descent. Coeliac Malabsorption is a state arising from abnormality in Digestion or Absorption of food nutrients across the gastrointestinal(GI tract. Allergy to gluten proteins, found in wheat, barley and rye, causes villous atrophy in the small intestine. Life-long dietary avoidance of these foodstuffs in a gluten-free diet is the only treatment.
Crohn's disease and ulcerative colitis are examples of inflammatory bowel disease. Crohn's disease is a Disease of the Digestive system which may affect any part of the Gastrointestinal tract from Mouth to Anus Ulcerative colitis ( Colitis ulcerosa, UC) is a form of Inflammatory bowel disease (IBD In Medicine, inflammatory bowel disease ( IBD) is a group of inflammatory conditions of the large intestine and Small intestine While Crohn's can affect the entire gastrointestinal tract, ulcerative colitis is limited to the large intestine. Crohn's disease is widely regarded as an autoimmune disease. Autoimmunity is the failure of an organism to recognize its own constituent parts as self, which results in an immune response against its own cells and tissues Although ulcerative colitis is often treated as though it were an autoimmune disease, there is no consensus that it actually is such. (See List of autoimmune diseases). Autoimmune diseases arise from an overactive Immune response of the body against substances and tissues normally present in the body
Enteroviruses are named by their transmission-route through the intestine (enteric = related to intestine), but their symptoms aren't mainly associated with the intestine. The enteroviruses are a genus of (+ssRNA viruses associated with several human and mammalian diseases

Disorders

Irritable bowel syndrome (IBS) is the most common functional disorder of the intestine. In Gastroenterology, irritable bowel syndrome ( IBS) is a Functional bowel disorder characterized by mild to severe Abdominal pain, discomfort Functional constipation and chronic functional abdominal pain are other disorders of the intestine that have physiological causes, but do not have identifiable structural, chemical, or infectious pathologies. Chronic functional abdominal pain (CFAP is the ongoing presence of Abdominal pain for which there is no known medical explanation They are aberrations of normal bowel function but not diseases.

Diverticular disease is a condition that is very common in older people in industrialized countries. Diverticulosis, otherwise known as " diverticular disease " is the condition of having diverticula in the colon which are outpocketings of the It usually affects the large intestine but has been known to affect the small intestine as well. Diverticular disease occurs when pouches form on the intestinal wall. Once the pouches become inflamed it is known as Diverticulitis, (or Diverticular disease. Diverticulitis is a common Digestive disease particularly found in the Large intestine. )

Endometriosis can affect the intestines, with similar symptoms to IBS. Endometriosis (from endo, "inside" and metra, " Womb " is a common medical condition characterized by growth beyond or outside the uterus

Bowel twist (or similarly, bowel strangulation) is a comparatively rare event (usually developing sometime after major bowel surgery). Bowel Infarction or 'bowel death' results from a severely restricted blood supply to part of the bowel this can in turn be due to an uncorrected bowel twist It is, however, hard to diagnose correctly, and if left uncorrected can lead to bowel infarction and death. In Medicine, an infarction is the process resulting in a Macroscopic area of necrotic tissue in some organ caused by loss of adequate Blood supply (The singer Maurice Gibb is understood to have died from this. Maurice Ernest Gibb CBE ( December 22 1949 &ndash January 12 2003) was a Musician and Singer-songwriter )

References

Encyclopædia Britannica article on intestine retrieved on 2007-03-27

^ Maton, Anthea; Jean Hopkins, Charles William McLaughlin, Susan Johnson, Maryanna Quon Warner, David LaHart, Jill D. Wright (1993). Human Biology and Health. Englewood Cliffs, New Jersey, USA: Prentice Hall. ISBN 0-13-981176-1.

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