Digestive System Topics
Food in the stomach that is partly digested and mixed with stomach acids is called chyme. Just before the connection to the stomach there is a "zone of high pressure," called the lower esophageal sphincter; this is a "valve" meant to keep food from passing backwards into the esophagus. After the food goes into the stomach, the muscles at the bottom of the stomach begin to move. Chemical digestion begins in the mouth with salivary amylase in saliva splitting complex carbohydrates into simple carbohydrates. The start of the process - the mouth: Besides aiding in the digestive process, the liver also stores nutrients and helps remove toxins from the body. There are many sections to the large bowel — the appendix, caecum, ascending rising colon, transverse across colon, descending going down colon, sigmoid colon, the rectum and the anus.
Description of the digestive system
Between the circular and longitudinal muscle layers is the myenteric plexus. Activity is initiated by the pacemaker cells, myenteric interstitial cells of Cajal. The gut has intrinsic peristaltic activity basal electrical rhythm due to its self-contained enteric nervous system. The rate can be modulated by the rest of the autonomic nervous system.
The coordinated contractions of these layers is called peristalsis and propels the food through the tract. Food in the GI tract is called a bolus ball of food from the mouth down to the stomach.
After the stomach, the food is partially digested and semi-liquid, and is referred to as chyme. In the large intestine the remaining semi-solid substance is referred to as faeces. The outermost layer of the gastrointestinal tract consists of several layers of connective tissue. Intraperitoneal parts of the GI tract are covered with serosa. These include most of the stomach , first part of the duodenum , all of the small intestine , caecum and appendix , transverse colon , sigmoid colon and rectum.
In these sections of the gut there is clear boundary between the gut and the surrounding tissue. These parts of the tract have a mesentery. Retroperitoneal parts are covered with adventitia.
They blend into the surrounding tissue and are fixed in position. For example, the retroperitoneal section of the duodenum usually passes through the transpyloric plane. These include the esophagus , pylorus of the stomach, distal duodenum , ascending colon , descending colon and anal canal.
In addition, the oral cavity has adventitia. Specific proteins expressed in the stomach and duodenum involved in defence include mucin proteins, such as mucin 6 and intelectin Finally, transit through the colon takes 12 to 50 hours with wide variation between individuals.
The gastrointestinal tract forms an important part of the immune system. There are additional factors contributing to protection from pathogen invasion. For example, low pH ranging from 1 to 4 of the stomach is fatal for many microorganisms that enter it. Beneficial bacteria also can contribute to the homeostasis of the gastrointestinal immune system.
For example Clostridia , one of the most predominant bacterial groups in the GI tract, play an important role in influencing the dynamics of the gut's immune system. This is due to the production of short-chain fatty acids during the fermentation of plant-derived nutrients such as butyrate and propionate. Basically, the butyrate induces the differentiation of Treg cells by enhancing histone H3 acetylation in the promoter and conserved non-coding sequence regions of the FOXP3 locus, thus regulating the T cells , resulting in the reduction of the inflammatory response and allergies.
The large intestine hosts several kinds of bacteria that can deal with molecules that the human body cannot otherwise break down. These bacteria also account for the production of gases at host-pathogen interface , inside our intestine this gas is released as flatulence when eliminated through the anus. However the large intestine is mainly concerned with the absorption of water from digested material which is regulated by the hypothalamus and the re absorption of sodium , as well as any nutrients that may have escaped primary digestion in the ileum.
Health-enhancing intestinal bacteria of the gut flora serve to prevent the overgrowth of potentially harmful bacteria in the gut. These two types of bacteria compete for space and "food," as there are limited resources within the intestinal tract. Enzymes such as CYP3A4 , along with the antiporter activities, are also instrumental in the intestine's role of drug metabolism in the detoxification of antigens and xenobiotics.
There are many diseases and conditions that can affect the gastrointestinal system, including infections , inflammation and cancer. Various pathogens can cause gastroenteritis an inflammation of the stomach and small intestine. These can include those organisms that cause foodborne illnesses. Gastroenteritis is the most common disease of the GI tract.
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. Diverticulosis occurs when pouches form on the intestinal wall. Once the pouches become inflamed it is known as diverticulitis. Inflammatory bowel disease is an inflammatory condition affecting the bowel walls, and includes the subtypes 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. Although ulcerative colitis is often treated as though it were an autoimmune disease, there is no consensus that it actually is such. Functional gastrointestinal disorders the most common of which is irritable bowel syndrome.
Functional constipation and chronic functional abdominal pain are other functional disorders of the intestine that have physiological causes, but do not have identifiable structural, chemical, or infectious pathologies.
Gastrointestinal surgery can often be performed in the outpatient setting. In the United States in , operations on the digestive system accounted for 3 of the 25 most common ambulatory surgery procedures and constituted 9. Various methods of imaging the gastrointestinal tract include the upper and lower gastrointestinal series:.
Animal intestines have multiple uses. From each species of livestock that is a source of milk , a corresponding rennet is obtained from the intestines of milk-fed calves. Pig and calf intestines are eaten, and pig intestines are used as sausage casings. Calf intestines supply calf-intestinal alkaline phosphatase CIP , and are used to make goldbeater's skin.
Many birds and other animals have a specialised stomach in the digestive tract called a gizzard used for grinding up food. Another feature not found in the human but found in a range of other animals is the crop. In birds this is found as a pouch alongside the esophagus. Other animals including amphibians , birds , reptiles , and egg-laying mammals have a major difference in their GI tract in that it ends in a cloaca and not an anus. From Wikipedia, the free encyclopedia.
Redirected from Human gastrointestinal tract. For other uses, see Guts disambiguation. Esophagus , Stomach , and duodenum. Development of the digestive system. Duct of gland outside tract 7: Gland in mucosa 8: Glands in submucosa Meissner's submucosal plexus Areolar connective tissue Auerbach's myenteric plexus Oral mucosa and Gastric mucosa.
Serous membrane and Adventitia. This section discusses related diseases, medical associations with the gastrointestinal tract, and use in surgery. Gastrointestinal disease and Gastroenterology. Ruminant and Methanogens in digestive tract of ruminants. This article uses anatomical terminology; for an overview, see Anatomical terminology.
Invertebrate Zoology 7 ed. Surgical and Radiologic Anatomy. Factor in achieving total enteroscopy? H; Fava, F; Hermes, G. M; Hold, G; Quraishi, M. G; Hart, A A new clinical frontier". The Neglected Endocrine Organ". Introduction to Behavioral Endocrinology. Retrieved 2 September Oxford textbook of medicine: Retrieved 1 July Mitchell; illustrations by Richard; Richardson, Paul Gray's anatomy for students 3rd ed. Human Embryology and Developmental Biology 3rd ed.
Histology and cell biology: From Bench Side to Bedside. Small intestine transit time in the normal small bowel study. American Journal of Roentgenology ; 3: Colonic Transit Study Technique and Interpretation: Scandinavian Journal of Gastroenterology. In the stomach - The stomach is a large, sack-like organ that churns the food and bathes it in a very strong acid gastric acid. Food in the stomach that is partly digested and mixed with stomach acids is called chyme.
In the small intestine - After being in the stomach, food enters the duodenum, the first part of the small intestine. It then enters the jejunum and then the ileum the final part of the small intestine. In the small intestine, bile produced in the liver and stored in the gall bladder , pancreatic enzymes, and other digestive enzymes produced by the inner wall of the small intestine help in the breakdown of food.
In the large intestine - After passing through the small intestine, food passes into the large intestine. In the large intestine, some of the water and electrolytes chemicals like sodium are removed from the food.
Many microbes bacteria like Bacteroides , Lactobacillus acidophilus , Escherichia coli , and Klebsiella in the large intestine help in the digestion process. The first part of the large intestine is called the cecum the appendix is connected to the cecum. Food then travels upward in the ascending colon. The food travels across the abdomen in the transverse colon, goes back down the other side of the body in the descending colon, and then through the sigmoid colon.
The end of the process - Solid waste is then stored in the rectum until it is excreted via the anus. In human beings, this is between the diaphragm and the pelvis alimentary canal - the passage through which food passes, including the mouth, esophagus, stomach, intestines, and anus.
Chyme goes on to the small intestine for further digestion. When you swallow, the epiglottis automatically closes. When you breathe, the epiglottis opens so that air can go in and out of the windpipe.
It uses rhythmic muscle movements called peristalsis to force food from the throat into the stomach. It stores and releases bile a digestive chemical which is produced in the liver into the small intestine. It filters toxins from the blood, and makes bile which breaks down fats and some blood proteins. Chewing and salivary enzymes in the mouth are the beginning of the digestive process breaking down the food.
Enzymes from the pancreas help in the digestion of carbohydrates, fats and proteins in the small intestine.
Peristalsis is involuntary - you cannot control it. It is also what allows you to eat and drink while upside-down. Saliva contains enzymes that break down carbohydrates starch into smaller molecules.