Diagram showing the small intestine

In biology the small intestine is the part of the gastrointestinal tract between the stomach and the large intestine (colon). In humans over 5 years old it is 5-6m long. It is divided into three structural parts: duodenum, jejunum and ileum. Food from the stomach is allowed in to the duodenum by a muscle called the pylorus, or pyloric sphincter, and is then pushed through the small intestine by a process of muscular contractions called peristalsis. Diagram of the stomach, colon and rectum from public domain source at http://www. ... Biology is the branch of science dealing with the study of life. ... The intestine is the portion 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. ... The gastrointestinal tract or digestive tract, also referred to as the GI tract or the alimentary canal or the gut, is the system of organs within multicellular animals which takes in food, digests it to extract energy and nutrients, and expels the remaining waste. ... In anatomy, the stomach (in ancient Greek στόμαχος) is an organ in the gastrointestinal tract used to digest food. ... In anatomy of the digestive system, the colon is the part of the intestine from the cecum to the rectum. ... Trinomial name Homo sapiens sapiens Linnaeus, 1758 Humans, or human beings, are biologically classified as bipedal primates belonging to the mammalian species Homo sapiens (Latin for wise man or thinking man) under the family Hominidae (the great apes). ... In anatomy of the digestive system, the duodenum is a hollow jointed tube connecting the stomach to the jejunum. ... Diagram of the Human Intestine 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 the ileum. ... Grays Fig. ... From Greek pylorus; pyl- = gate, -orus = guard. ... From Greek pylorus; pyl- = gate, -orus = guard. ... Peristalsis is the process of involuntary wave-like successive muscular contractions by which food is moved through the digestive tract. ...

The small intestine is the site where most of the nutrients from ingested food are absorbed. There are microscopic finger-like projections called villi covering the small intestinal walls which increase surface area for absorption. Each villus contains a lacteal and capillaries. The lacteal absorbs the digested fat into the lymphatic system which will eventually drain into the circulatory system. The capillaries absorb all other digested nutrients. Villi (singular: villus) are tiny, finger-like structures that protrude from the wall of the intestine to help absorb nutrients in the lumen. ... A lacteal is found in the small intestine. ... This article or section is in need of attention from an expert on the subject. ... Lymph originates as blood plasma lost from the circulatory system, which leaks out into the surrounding tissues. ... Human circulatory system. ... // Nutrients and the body A nutrient is any element or compound necessary for or contributing to an organisms metabolism, growth, or other functioning. ...

Although the small intestine is much longer than the large intestine (typically 4-5 times the length of the large intestine), it is referred to as such due to its comparatively smaller diameter. On average, the diameter of the large intestine of an adult human measures approximately 3 times the diameter of the small intestine. Upon viewing accurate diagrams of the digestive system, non-medically trained personnel often initially express bemusement as to why the obviously longer portion of the digestive system is referred to as the small intestine. In anatomy of the digestive system, the colon is the part of the intestine from the cecum to the rectum. ...

Functions

In the small intestine, proteins are changed into amino acids; fats are changed into fatty acids; and carbohydrates are changed into glucose. The small intestine is also the place where the most chemical digestion takes place.(From Encyclopædia Britannica School Edition)

The largest amount of water from the chyme(the substance that comes from the stomach) is absorbed in the small intestine. Chyme is the liquid substance found in the stomach before passing the pyloric valve and entering the duodenum. ...

Small Intestine Disorders

(see also gastroenterology) Gastroenterology or gastrology is the medical specialty concerned with the field of digestive diseases. ...

• small intestine obstruction ("high" mechanic ileus)
  • volvulus
  • obstruction from external pressure
  • obstruction by masses in the lumen (foreign bodies, bezoar, gallstones)
• paralytic ileus
• Crohn's disease
• celiac disease
• carcinoid
• Meckel's Diverticulum
• gastric dumping syndrome
• infectious diseases
  • giardiasis
  • ascaridosis
  • tropical sprue
  • tapeworm infection
• mesenteric ischemia
• short bowel syndrome

A volvulus is a loop of bowel that has twisted on itself, possibly resulting in loss of blood flow to part or all of the intestines (strangulation). ... The word Foreign means originating elsewhere or in the physiological context outside the body. ... A bezoar or enterolith is a sort of calculus or concretion, a stone found in the intestines of mostly ruminant animals. ... In medicine, gallstones (choleliths) are crystalline bodies formed within the body by accretion or concretion of normal or abnormal bile components. ... Diagram of the Human Intestine Crohns disease is a chronic inflammatory disease that can involve any part of the digestive tract, from the mouth to the anus. ... Coeliac disease (also termed non-tropical sprue, celiac disease and gluten intolerance) is an autoimmune disease characterised by chronic inflammation of the proximal portion of the small intestine caused by exposure to certain dietary gluten proteins. ... Carcinoid is a potentially malignant tumour that occurs in the mucosa of the lungs and digestive tract and potentially in other organs. ... A Meckels diverticulum is a true congenital diverticulum. ... Gastric dumping syndrome, or rapid gastric emptying, happens when the lower end of the small intestine, the jejunum, fills too quickly with undigested food from the stomach. ... In medicine, infectious disease or communicable disease is disease caused by a biological agent (e. ... Giardiasis (also known as beaver fever) is a disease caused by the flagellate protozoan Giardia lamblia (also Giardia intestinalis). ... Tropical sprue is a malabsorption disease commonly found in the tropical regions, marked with abnormal flattening of the villi and inflammation of the lining of the small intestine. ... Adult tapeworm infection is the infection of the digestive tract by parasitic flatworms called cestodes or tapeworms. ... Short bowel syndrome is a malabsorption disorder caused by either the surgical removal of the small intestine or the loss of its absorptive function due to diseases. ...

References

Solomon et. al (2002) Biology Sixth Edition, Brooks-Cole/Thomson Learning ISBN 0-03-033503-5

See also

• Intestinal juice
• Colon (anatomy)

Intestinal juice (succus entericus) refers to the clear to pale yellow watery secretions from the glands lining the small intestine walls. ... Grays Fig. ...

External Links

• Small Intestine from the Gray's Anatomy eBook