Intestine

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Structure and function

Gross anatomy

Microanatomy

• Along the whole length of the gut in the glandular epithelium are goblet cell
  Goblet cell
  
  Goblet cells are glandular simple columnar epithelium Cell whose sole function is to secrete mucus. They use both apocrine and merocrine methods for secretion....
  s. These secrete 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,...
   which lubricates the passage of food along and protects it from digestive enzymes. Villi are vaginations of the mucosa
  Mucous membrane
  
  The mucous membranes are linings of mostly germ layer origin, covered in epithelium, which are involved in absorption and secretion. They line various body cavities that are exposed to the external environment and internal organ ....
   and increase the overall surface area of the intestine while also containing a lacteal
  Lacteal
  
  A lacteal is a lymphatic that absorbs dietary fats in the villi of the small intestine.The combination of fat and lymph in the lacteals is milky in appearance and called chyle....
  , which is connected to the lymph system
  Lymphatic system
  
  The lymphatic system in vertebrates is a network of conduits that carry a clear fluid called lymph. It also includes the lymphoid tissue through which the lymph travels....
   and aids in the removal 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....
  s and tissue fluid from the blood supply. 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
  Gastrointestinal tract
  
  The digestive tract is the system of Organ s within multicellular animals that takes in food, digestion it to extract energy and nutrients, and expels the remaining waste....
   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
  Gastrointestinal tract
  
  The digestive tract is the system of Organ s within multicellular animals that takes in food, digestion it to extract energy and nutrients, and expels the remaining waste....
   which comprises longitudinal and smooth muscle that again helps with continued peristalsis and the movement of digested material out of and along the g.

• Lastly there is the serosa
  Serous membrane
  
  In anatomy, a serous membrane is a smooth Mesothelium consisting of a thin layer of Cell which excrete serous fluid. Serous membranes line and enclose several body cavities, known as serous cavities, where they secrete a lubricating fluid which reduces friction from muscle movement....
   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. Holding all this in place are the mesenteries
  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....
   which suspend the intestine in the abdominal cavity and stop it being disturbed when a person is physically active.

Diseases

• Gastroenteritis
  Gastroenteritis
  
  Gastroenteritis is inflammation of the gastrointestinal tract, involving both the stomach and the small intestine and resulting in acute diarrhea....
   is inflammation of the intestines and is the most common disease of the intestines.
• Ileus
  Ileus
  
  Ileus is a disruption of the normal propulsive gastrointestinal tract motor activity from non-mechanical mechanisms. Motility disorders that result from structural abnormalities are termed mechanical bowel obstruction....
   is a blockage of the intestines.
• Ileitis
  Ileitis
  
  Ileitis is an inflammation of the ileum, a portion of the small intestine. Crohn's ileitis is a type of Crohn's disease affecting the ileum....
   is an inflammation of the 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....
  .
• Colitis
  Colitis
  
  Colitis is a Chronic digestive diseases characterized by inflammation of the colon .Colitis is one of a group of conditions which are inflammatory and auto-immune, affecting the tissue that lines the gastrointestinal system ....
   is an inflammation of 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....
  .
• Appendicitis
  Appendicitis
  
  Appendicitis is a condition characterized by inflammation of the Vermiform appendix. It is a medical emergency. All cases require removal of the inflamed appendix, either by laparotomy or laparoscopy....
   is inflammation of 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 ....
   located at the caecum. This is a potentially fatal disease if left untreated; most cases of appendicitis require surgical intervention.
• Coeliac disease
  Coeliac disease
  
  C?liac disease , also spelled celiac disease, is an Autoimmunity disorder of the small intestine that occurs in Genetic predisposition people of all ages from middle infancy on up....
   is a common form of malabsorption
  Malabsorption
  
  Malabsorption is a state arising from abnormality in digestion or absorption of Nutrient across the gastrointestinal tract.Impairment can be of single or multiple nutrients depending on the abnormality....
  , affecting up to 1% of people of northern European descent. 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
  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....
   are examples of 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.....
  . 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
  
  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).
• Enteroviruses are named by their transmission-route through the intestine (enteric = related to intestine), but their symptoms aren't mainly associated with the intestine.

Disorders

• 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....
   (IBS) is the most common functional disorder of the intestine. Functional constipation and chronic functional abdominal pain
  Chronic functional abdominal pain
  
  Chronic functional abdominal pain is the ongoing presence of abdominal pain for which there is no known medical explanation. It is quite similar to, but less common than, irritable bowel syndrome , and many of the same treatments for IBS can also be of benefit to those with CFAP....
   are other disorders of the intestine that have physiological causes, but do not have identifiable structural, chemical, or infectious pathologies. 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. 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
  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 ....
  , (or Diverticular disease.)

• Endometriosis
  Endometriosis
  
  Endometriosis is a medical condition in women in which endometrial cells are deposited in areas outside the uterine cavity. The uterine cavity is lined by endometrial cells, which are under the influence of female hormones....
   can affect the intestines, with similar symptoms to IBS.

• Bowel twist (or similarly, bowel strangulation) is a comparatively rare event (usually developing sometime after major bowel surgery). It is, however, hard to diagnose correctly, and if left uncorrected can lead to bowel infarction
  Infarction
  
  In medicine, an infarction results in the death of a macroscopic area of tissue in an organ due to loss of adequate blood supply. This dead tissue is then known as necrosis....
   and death. (The singer Maurice Gibb
  Maurice Gibb
  
  Maurice Ernest Gibb Order of the British Empire was a musician and singer-songwriter. He was born in Douglas, Isle of Man, Isle of Man, the twin brother of Robin Gibb, and younger brother to Barry Gibb....
   is understood to have died from this.)

See also

• 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.....
   (or "IBD")
• Diarrhea
  Diarrhea
  
  In medicine, diarrhea, also spelled diarrhoea , is characterized by frequent loose or liquid bowel movements. The spelling of "diarrhea" is an appropriation of the Greek "diarrhoia" meaning "a flowing through." ....
  
• Constipation
  Constipation
  
  Constipation, costiveness, or irregularity, is a condition of the digestive system in which a person experiences hard feces that are difficult to expel....