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The human digestive system consists of the digestive tract plus the digestive accessory organs (tongue, salivary glands, pancreas, liver, and gallbladder). In this system, the process of digestion has many stages, the first begins in the mouth. Digestion involves breaking down food into smaller and smaller components, until they can be absorbed and assimilated into the body.
Chewing, where food is mixed with saliva begins the digestive process. This produces a bolus that can be swallowed into the esophagus and into the stomach. Here it is mixed with gastric juice until it enters the duodenum where it is mixed with a number of enzymes produced by the pancreas. Saliva also contains a catalytic enzyme called amylase that begins to act on the food in the mouth. Another digestive enzyme called lingual lipase is secreted by several lingual papillae on the tongue and also from the serous glands in the major salivary glands. Digestion is aided by food chewing by teeth and also by peristaltic muscle action and contraction of segmentation. Gastric juice in the stomach is very important for the continuation of digestion such as the production of mucus in the stomach.
Peristalsis is a rhythmic contraction of the muscles that begin in the esophagus and continues along the wall of the stomach and the rest of the gastrointestinal tract. It initially results in the production of chyme which when completely damaged in the small intestine is absorbed as chyle into the lymphatic system. Much of the digestion of food takes place in the small intestine. Water and some minerals are absorbed back into the blood in the colon's large intestine. The product of digestion waste (waste) is removed from the anus through the rectum.
Video Human digestive system
Components
There are several organs and other components involved in the digestion of food. Organs known as accessory digestive glands are the liver, gallbladder and pancreas. Other components include the mouth, salivary glands, tongue, teeth and epiglottis.
The biggest structure of the digestive system is the digestive tract (gastrointestinal tract). It starts in the mouth and ends in the anus, which covers a distance of about nine (9) meters.
The largest part of the gastrointestinal tract is the colon or colon. Water is absorbed here and residual waste is stored before defecation.
Much of the digestion of food takes place in the small intestine.
The main digestive organs are the stomach. Inside the mucosa there are millions of stomach glands that are embedded. Their secretions are very important for organ function.
There are many specialized cells of the digestive tract. These include various cells of the gland, tasting cells, pancreatic duct cells, enterocytes and microfolder cells.
Some parts of the digestive system are also part of the excretory system, including the colon.
Mouth
The mouth is the first part of the gastrointestinal tract and comes with several structures that begin the first digestive process. These include the salivary glands, teeth and tongue. The mouth consists of two regions; the right front room and oral cavity. Vestibulum is the area between the teeth, lips and cheeks, and the rest is the right oral cavity. Most oral cavities are coated with oral mucosa, mucous membranes that produce lubricating mucus, which only a small amount is required. Mucous membranes vary in structure in different areas of the body but they all produce mucus lubricants, which are either secreted by surface cells or more usually by the underlying glands. The mucous membrane in the mouth continues as a thin mucosa that covers the basics of teeth. The main component of mucus is a glycoprotein called mucin and the secreted type varies according to the region involved. Mucin is thick, clear, and clingy. The underlying mucous membrane in the mouth is a thin layer of smooth muscle tissue and loose connections to the membrane provide great elasticity. Includes the cheek, the inner surface of the lips, and the base of the mouth.
The roof of the mouth is called the ceiling and it separates the oral cavity from the nasal cavity. The ceiling is hard in front of the mouth because the mucosa above it covers a plate of bones; it is softer and more flexible on the back that is made of muscle and connective tissue, and can move to swallow food and fluids. The soft palate ends in uvula. The hard palate surface allows for the pressure required in eating food, to leave a clean nose section. The lips are the front border of the mouth and fauces (the channel between the tonsils, also called the throat), marking the posterior border.
On either side of the soft palate is the palatoglossus muscle that also reaches the tongue region. These muscles lift the back of the tongue and also close both sides of the fauces to allow food to be swallowed. Mucus assists in the mastery of food in its ability to soften and collect food in bolus formation.
Salivary glands
There are three pairs of major salivary glands and between 800 and 1,000 small salivary glands, all of which primarily serve the digestive process, and also play an important role in maintaining oral hygiene and general lubrication, without which it is impossible to speak. The main gland is the exocrine gland, which secretes through the channel. All these glands stop in the mouth. The biggest are the parotid glands - their secretions are mainly serous. The next pair is under the jaw, the submandibular gland, this produces serous fluid and mucus. Serous fluids are produced by the serous glands in the salivary glands that also produce lingual lipases. They produce about 70% of the saliva of the oral cavity. The third pair is a sublingual gland located under the tongue and their secretions are mainly mucus with a small percentage of saliva.
In the oral mucosa (mucous membranes) that coat the mouth and also on the tongue and the palate and floor of the mouth, is a small salivary gland; their secretions are mainly mucus and innervated by the facial nerve (seventh cranial nerve). The glands also release the first stage of amylase in the breakdown of foods that work on carbohydrates in foods to convert starch content to maltose. There is another gland on the surface of the tongue that surrounds the tongue tongue on the back of the tongue and this also produces lingual lipase. Lipase is a digestive enzyme that catalyzes lipid hydrolysis (fat). This gland is called the Von Ebner gland which has also been shown to have other functions in histatins secretions that offer an early defense (outside the immune system) to the microbes in the diet, when making contact with these glands on the tongue tissue. Sensory information can stimulate the secretion of saliva that provides the fluid that the tongue needs to work and also to ease the food swallow.
Saliva
Saliva wets and softens food, and along with chewing gears, turning food into fine bolus. Bolus is further assisted by the lubrication provided by saliva in its path from the mouth to the esophagus. Also important is the presence of saliva enzyme digestion of amylase and lipase. Amylase begins to work on starches with carbohydrates, breaking them into simple sugars of maltose and dextrose that can be further described in the small intestine. Saliva in the mouth can reach 30% of this starch digestion. Lipase starts to work to break down fat. Lipase is produced further in the pancreas where it is released to continue digestion of these fats. The presence of salivary lipase is very important in young infants whose pancreatic lipases have not been developed.
As well as its role in supplying digestive enzymes, saliva has a cleansing action for teeth and mouth. It also has an immunological role in supplying antibodies to the system, such as immunoglobulin A. This appears to be a key in preventing salivary gland infection, most importantly from parotitis.
Saliva also contains a glycoprotein called haptocorrin which is a binding protein for vitamin B 12 . It binds with vitamins to carry them safely through the acid content of the stomach. When it reaches the duodenum, the pancreatic enzyme breaks down the glycoprotein and liberates the vitamin which then binds to the intrinsic factor.
Tongue
Food enters the mouth where the first stage in the digestive process occurs, with tongue action and salivary secretion. The tongue is a muscular organ that is muscular and muscular, and the first sensory information is received through the tasting in the papilla on its surface. If it tastes good, the tongue will act, manipulating the food in the mouth that stimulates salivary secretion from the salivary glands. The quality of the saliva will help in the softening of the food and its enzyme content will begin to break down food while still in the mouth. The first part of the food that is broken down is carbohydrate starch (by the enzyme amylase in the saliva).
The tongue is attached to the bottom of the mouth by a ribbon of ligament called frenum and this gives great mobility for the manipulation of food (and speech); the range of manipulation is optimally controlled by the action of some muscles and limited in its external range by the frenum stretch. Two sets of tongue muscles, are four intrinsic muscles that originate from the tongue and are involved with its formation, and four extrinsic muscles derived from the bones involved with its movement.
Taste
Taste is a form of chemoreception that occurs in a special taste receptor, which is contained in a structure called taster in the mouth. Taste flavors especially on the upper surface (dorsum) of the tongue. The function of taste perception is very important to help prevent harmful or foul food from consumed. There is also a taster on the epiglottis and the top of the esophagus. The tastes are innervated by the branches of the chorda tympani facial nerve, and the glossopharyngeal nerve. Flavor messages are sent through this cranial nerve to the brain. The brain can differentiate between the chemical qualities of food. These five basic tastes are called saltiness, sour, bitterness, sweetness, and umami. Salty and acid detection allows the control of the salt and acid balance. Bitter detection warns of toxins - many plant defenses are bitter toxic compounds. A sweet guide to food that will supply energy; the initial breakdown of carbohydrates that energize by salivary amylase creates a sweet taste because simple sugars are the first result. Umami taste is considered to signal protein rich foods. Acidic flavor is often found in bad foods. The brain must decide quickly whether food should be eaten or not. It was a finding in 1991, explaining the first olfactory receptor that helped push the research into flavor. The olfactory receptor is located on the surface of the cells in the nose that binds chemicals allowing odor detection. It is thought that signals from taste receptors work together with those from the nose, to form the idea of ​​a complex food flavor.
Dental
Teeth are complex structures made of special materials for them. They are made of a material like bone called dentin, which is covered by the most difficult tissue in the body - enamel. Teeth have different shapes to deal with different aspects of mastication used in tearing and chewing pieces of food into smaller and smaller pieces. This results in a much larger surface area for the work of digestive enzymes. Teeth are named after their special role in the mastication process - incisors are used to cut or bite pieces of food; canine teeth, used for tearing, premolars and molars used for chewing and grinding. Mastication of food with the help of saliva and mucus results in the formation of soft bolus which can then be swallowed to make the way down the upper gastrointestinal tract to the stomach. Digestive enzymes in saliva also help keep your teeth clean by breaking nested food particles.
Epiglottis
Epiglottis is an elastic cartilage flap attached to the entrance of the larynx. It is covered with a mucous membrane and there is a taster on its lingual surface that faces the mouth. The laryngeal surface faces the larynx. Epiglottis serves to guard the glottic entrance, opening between the vocal cords. It usually points upward when breathing with its lower function as part of the pharynx, but during swallowing, the epiglottis folds downward to a more horizontal position, with the upper side acting as part of the pharynx. This prevents food from entering the trachea and instead directs it to the esophagus, which is behind. During swallowing, reverse movement of the tongue forces the epiglottis above the glottic opening to prevent any food swallowed into the larynx that leads to the lungs; The larynx is also pulled up to help this process. Stimulation of the larynx with ingested ingredients produces a strong cough reflex to protect the lungs.
Pharynx
Pharynx is part of the respiratory system conduction zone and is also part of the digestive system. This is part of the throat immediately behind the nasal cavity at the back of the mouth and above the esophagus and larynx. The pharynx consists of three parts. The lower two - oropharynx and laryngopharynx are involved in the digestive system. The laryngopharynx is connected to the esophagus and serves as a hallway for air and food. Air enters the larynx on the front but anything that is swallowed has priority and the air duct is temporarily blocked. Pharynx is innervated by the pharyngeal plexus of the vagus nerve. The muscles in the pharynx push the food into the esophagus. The pharynx joins the esophagus in the esophageal inlet located behind the cricoid cartilage.
Esophagus
The esophagus, commonly known as the throat, is an organ consisting of a muscle tube in which food moves from the pharynx to the stomach. The esophagus is continuous with the laryngeal part of the pharynx. It passes the posterior mediastinum in the thorax and enters the stomach through a hole in the thoracic diaphragm - the esophageal hiatus, at the level of the tenth thoracic vertebrae (T10). The length is an average of 25 cm, varying by height. It is divided into parts of the cervix, thorax and stomach. The pharynx joins the esophagus in the esophageal inlet located behind the cricoid cartilage.
When the esophageal rest is closed at both ends, by the upper and lower esophageal sphincters. The opening of the upper sphincter is triggered by a swallowing reflex so that food is allowed to enter. Sphincters also serve to prevent backflow from the esophagus to the pharynx. The esophagus has a mucous membrane and an epitelium that has a protective function constantly replaced due to the volume of food entering the esophagus. During swallowing, food passes through the mouth through the pharynx to the esophagus. The epiglottis folds down to a more horizontal position preventing food from entering the trachea, instead leading it to the esophagus.
Once in the esophagus, the bolus moves to the stomach through rhythmic contraction and muscle relaxation known as peristaltic motion. The lower esophageal sphincter is the sphincter muscle that surrounds the lower part of the esophagus. The junction between the esophagus and the stomach (gastroesophageal junction) is controlled by the lower esophageal sphincter, which remains narrowed at any time other than during swallowing and vomiting to prevent the contents of the stomach entering the esophagus. Because the esophagus does not have the same protection from acid as the stomach, the failure of this sphincter can cause heartburn. The esophagus has an epithelial mucous membrane that has a protective function and provides a smooth surface for food travel. Due to the high volume of food that passes through time, this membrane is constantly updated.
Diaphragm
Diaphragms are an important part of the body's digestive system. The muscle diaphragm separates the thoracic cavity from the abdominal cavity where most of the digestive organs are located. The suspensory muscle is attached to the duodenum ascending to the diaphragm. This muscle is considered to be helpful in the digestive system because its attachment offers a wider angle to the duodenojejunal bending to facilitate circulation of the digestive material. Diaphragms are also attached, and anchor the heart in the naked area. The esophagus enters the stomach through the aperture of the diaphragm at level T10.
Stomach
The abdomen is the main organ of the digestive tract and the digestive system. This is a consistent J-shaped organ that joins into the esophagus at its upper end and into the duodenum at its lower end. Stomach acid (informally stomach juice ), produced in the stomach plays an important role in the digestive process, and mainly contains hydrochloric acid and sodium chloride. Peptide hormone, gastrin, produced by G cells in the gland, stimulates the production of gastric juice that activates digestive enzymes. Pepsinogen is a precursor enzyme (zymogen) produced by stomach head cells, and gastric acid activates this to the enzyme pepsin which initiates protein digestion. Since both of these chemicals will damage the stomach wall, the mucus is secreted by innumerable gastric glands in the stomach, to provide a slimy protective layer against the detrimental effects of chemicals on the inner lining of the stomach.
At the same time that proteins are being digested, mechanical spins occur via peristaltic action, waves of muscle contractions that move along the wall of the stomach. This allows the mass of food to mix further with digestive enzymes. The gastric lipase secreted by the major cells in the fundus gland in the gastric mucosa, is the acid lipase, in contrast to the basic pancreatic lipase. It breaks down fat to some degree even though it is not as efficient as pancreatic lipase.
Pilorus, the lowest portion of the stomach attached to the duodenum through the pylorus channel, contains innumerable glands that secrete digestive enzymes including gastrin. After an hour or two, a thick, semi-liquid chyme is produced. When the pyloric sphincter, or valve is open, the chyme enters the duodenum where it mixes further with the digestive enzyme of the pancreas, and then passes through the small intestine, where the digestion continues. When the chyme is fully digested, it is absorbed into the blood. 95% absorption of nutrients occurs in the small intestine. Water and minerals are absorbed back into the blood in the large intestine, where the environment is slightly acidic. Some vitamins, such as biotin and vitamin K produced by bacteria in the intestinal flora of the colon are also absorbed.
Parietal cells in the fundus of the stomach, producing a glycoprotein called intrinsic factor are important for the absorption of vitamin B12. Vitamin B12 (cobalamin), carried to, and through the stomach, is bound to a glycoprotein secreted by the salivary glands - my transcobalamin is also called haptocorrine, which protects the acid-sensitive vitamins from the acid's contents. After being in the more neutral duodenum, pancreatic enzymes break down protective glycoproteins. The liberated vitamin B12 then binds to the intrinsic factor which is then absorbed by the enterocytes in the ileum.
The abdomen is an organ that can be distensible and can usually be expanded to accommodate about one liter of food. This expansion is made possible by a series of gastric folds on the inner abdominal wall. The newborn's belly will only expand to maintain about 30 ml.
Spleen
The spleen breaks red and white blood cells that are spent . This is why it is sometimes known as the 'red blood cell tomb'. The product of this digestion is the bilirubin pigment, which is sent to the liver and secreted in the bile. Another product is iron, which is used in the formation of new blood cells in the bone marrow. Treatment treats the spleen solely as belonging to the lymphatic system, although it is recognized that many important functions are not yet understood. Liver
The liver is the second largest organ (after the skin) and is an accessory digestive gland that plays a role in the body's metabolism. The liver has many functions that are essential for digestion. The liver can detoxify various metabolites; synthesize proteins and produce the biochemistry necessary for digestion. It regulates the storage of glycogen that can be formed from glucose (glycogenesis). The liver can also synthesize glucose from certain amino acids. Its digestive function is mostly involved with breaking down carbohydrates. It also maintains protein metabolism in its synthesis and degradation. In lipid metabolism it synthesizes cholesterol. Fat is also produced in the process of lipogenesis. The liver synthesizes most of the lipoproteins. The liver is located in the upper right quadrant of the abdomen and under the diaphragm attached to one part, This is to the right of the stomach and it lining the gallbladder. The liver produces bile, an important base compound that helps digestion.
Bile
The bile produced by the liver consists of water (97%), bile salts, mucus and pigment, 1% fat and inorganic salts. Bilirubin is the main pigment. The bile acts partly as a surfactant that lowers the surface tension between two liquids or solids and liquids and helps emulsify the fat in the chyme. Food fat is dispersed by the action of bile into smaller units called micelles. Breaking into micelles creates a much larger surface area for pancreatic enzymes, lipases to work on. Lipase digests triglycerides that are broken down into two fatty acids and monoglycerides. This is then absorbed by the villi in the intestinal wall. If the fat is not absorbed in this way in small bowel problems may occur later in the large intestine that is not equipped to absorb fat. Bile also helps in the absorption of vitamin K from food. Galls are collected and transmitted through common liver channels. This channel joins the cystic ducts to connect in the bile duct alongside the gallbladder. Bile is stored in the gallbladder to be released when food is discharged into the duodenum and also after a few hours.
Gallbladder
The gallbladder is an empty part of the bile ducts located just below the liver, with the gallbladder body resting in a small depression. This is the small organ in which the bile produced by the liver is stored, before it is released into the small intestine. Bile flows from the liver through the bile duct and into the gallbladder for storage. Bile is released in response to cholecystokinin (CCK), a peptide hormone released from the duodenum. The production of CCK (by endocrine cells of the duodenum) is stimulated by the presence of fat in the duodenum.
It is divided into three parts, fundus, body and neck. The neck narrows and connects to the bile ducts through the cystic tract, which then joins the common liver ducts to form the bile ducts. At this junction there is a mucous fold called the Hartmann pouch, where the gallstones are usually stuck. The body's muscular layer is the smooth muscle tissue that helps contract the gallbladder, so it can secrete bile into the bile ducts. The gallbladder needs to store bile in its natural semi-liquid form at all times. Hydrogen ions secreted from the inner layer of the gall bladder keep the bile acidic enough to prevent hardening. To dilute the bile, water and electrolytes from the digestive system are added. Also, the salt attaches to the cholesterol molecules in the bile to keep them from crystallizing. If there is too much cholesterol or bilirubin in the bile, or if the gallbladder does not empty properly, the system may fail. This is how gallstones form when a small piece of calcium is coated with cholesterol or bilirubin and bile crystallizes and forms a gallstone. The main purpose of the gallbladder is to store and release bile, or bile . Bile is released into the small intestine to help digest fat by breaking larger molecules into smaller ones. After the fat is absorbed, the bile is also absorbed and transported back to the liver for reuse.
Pancreas
The pancreas is the main organ that acts as an accessory digestive gland in the digestive system. These are the endocrine glands and exocrine glands. The endocrine part secretes insulin when blood sugar becomes high; insulin moves glucose from blood to muscles and other tissues to use as energy. The endocrine part releases glucagon when blood sugar is low; glucagon allows the stored sugar to be broken down into glucose by the liver to rebalance the sugar content. The pancreas produces and releases an important digestive enzyme in the pancreatic juice it provides to the duodenum. The pancreas is located below and at the back of the abdomen. It connects to the duodenum through the pancreatic duct that joins near the bile duct connections where both bile and pancreatic juice can act on chyme released from the stomach to the duodenum. The secretion of the aqueous pancreas from the pancreatic duct cells contains alkaline bicarbonate ions and helps bile to neutralize the acid chyme rotated by the stomach.
The pancreas is also a major source of enzymes for the digestion of fats and proteins. Some of these are released in response to CKK production in the duodenum. (Enzymes that digest polysaccharides, on the other hand, are mainly produced by the intestinal wall.) The cells are filled with secretory granules containing the precursor digesting enzyme. The main protease, the pancreatic enzyme that acts on proteins, is trypsinogen and chymotrypsinogen. Elastase is also produced. Smaller amounts of lipase and amylase are secreted. The pancreas also secretes A2 phospholipase, lysophospholipase, and cholesterol esterase. Zimogen predecessor, is a variant of inactive enzymes; which avoids the onset of pancreatitis caused by autodegradation. Once released in the intestine, the enteropeptidase enzyme present in the intestinal mucosa activates trypsinogen by splitting it to form trypsin; Further division produces chymotripsin.
Lower gastrointestinal tract
Lower gastrointestinal tract (GI), including the small intestine and all the colon. The intestine is also called the intestines or intestines. The lower GI begins in the stomach pyloric sphincter and ends at the anus. The small intestine is divided into duodenum, jejunum and ileum. The cecum marks the division between the small and large intestines. The large intestine includes the rectum and anal canal.
Small intestine
Food begins to arrive in the small intestine an hour after eating, and after two hours the stomach is empty. Until now the food is called bolus. Then it becomes a semi-liquid chyme called partially digested.
In the small intestine, pH becomes important; it needs to be balanced well to activate the digestive enzymes. Chyme is very acidic, with low pH, once released from the stomach and needs to be made more alkaline. This is achieved in duodenum by the addition of bile from the gallbladder combined with bicarbonate secretion from the pancreatic ducts and also from the secretion of rich mucarbonate mucus from the duodenal gland known as the Brunner gland. Chyme arrives in the intestine after being released from the stomach through the opening of the pyloric sphincter. The resulting alkaline mixture neutralizes the stomach acid which will damage the lining of the intestine. The mucus component lubricates the intestinal wall.
When digested food particles are reduced sufficiently in size and composition, they can be absorbed by the intestinal wall and brought into the bloodstream. The first container for this chyme is a duodenal ball. From here passes to the first of three parts of the small intestine, the duodenum. (The next section is jejunum and the third is ileum) . Duodenum is the first and shortest part of the small intestine. This is a c-shaped tube that connects the stomach to the jejunum. It starts on the duodenum and ends in the duodenal suspensory muscle. The attachment of the suspensory muscle to the diaphragm is thought to help travel the food by making a wider angle to its clinging.
Much of the digestion of food takes place in the small intestine. The segmentation contraction acts to mix and move the chyme more slowly in the small intestine which allows more time for absorption (and this continues in the colon). In the duodenum, pancreatic lipase is secreted along with co-enzyme, collagenase to further digest chyme fat content. From this damage, tiny particles of fatty emulsion called kilomikron are produced. There are also digestive cells called enterocytes that line the intestines (the majority are in the small intestine). They are unusual cells because they have villous on the surface which in turn has countless microvilli on its surface. All these villi make a larger surface area, not only for chyme absorption but also for further digestion by a large number of digestive enzymes present in microvilli.
The kilomikron is small enough to pass through the enterocyte villi and into their lymph capillaries called lacteal. The milk fluid is called chyle, mainly composed of emulsion fat from kilomikron, the result of a mixture absorbed with lymph in lacteal. Chyle is then transported through the lymphatic system throughout the body.
The suspensory muscle marks the end of the duodenum and the division between the upper gastrointestinal tract and the lower digestive tract. The digestive tract continues as a jejunum that continues as an ileum. Jejunum, the central part of the small intestine contains circular folds, folds of double mucous membranes that partially surround and sometimes surround the intestinal lumen. These folds along with the villi serve to increase the surface area of ​​the jejunum which allows increased absorption of the digestible sugars, amino acids and fatty acids into the bloodstream. The circular crease also slows down the food journey which gives more time for absorbed nutrients.
The last part of the small intestine is the ileum. It also contains villi and vitamin B12; bile acids and all residual nutrients are absorbed here. When the chyme is depleted of nutrients, the remaining waste material becomes semi-solid called faeces, which pass into the large intestine, where bacteria in the intestinal flora break down the rest of the protein and starch.
Cecum
The cecum is a bag that marks the division between the small intestine and the large intestine. The serum receives a chyme from the last part of the small intestine, ileum, and connects it to the ascending colon. At this junction there is a sphincter or valve, an ileocecal valve that slows the chyme journey from the ileum, allowing further digestion. This is also a attachment attachment site.
Colon
In the large intestine, the digestible food travel in the colon is much slower, taking from 12 to 50 hours until it is removed by a bowel movement. The colon mainly serves as a site for the fermentation of materials that can be ingested by intestinal flora. The time required varies between individuals. The residual semi-solid waste is called feces and is removed by a coordinated contraction of the intestinal wall, called the peristaltic, which pushes the excavate forward to reach the rectum and out through the bowel movement of the anus. The walls have longitudinal muscle outer layers, taeniae coli, and circular muscle layers. The circular muscles make the material move forward and also prevent backflow of waste. Also helpful in the peristaltic action is the basal electric rhythm that determines the frequency of contraction. Taeniae coli can be seen and is responsible for the bulge (haustra) present in the colon. Most of the digestive tract is covered with serous membranes and has mesentery. The more muscular part is lined with adventitia.
Maps Human digestive system
Blood supply
The digestive system is supplied by the celiac artery. The celiac artery is the first major branch of the abdominal aorta, and is the only major artery that nourishes the digestive organs.
There are three main divisions - left gastric artery, common hepatic artery and spleen artery.
The celiac artery supplies the liver, stomach, spleen and the upper half of the duodenum (to the Oddi sphincter) and the pancreas with oxygenated blood. Much of the blood is returned to the liver via the portal vein system for further processing and detoxification before returning to the systemic circulation via the hepatic vein.
The next branch of the abdominal aorta is the superior mesenteric artery, which supplies the gastrointestinal tract originating from the midgut, which includes 2/3 of the distal portion of the duodenum, jejunum, ileum, cecum, appendix, ascending colon, and proximal 2/3 of the colon transversum.
The last important branch for the digestive system is the inferior mesenteric artery, which supplies the digestive tract region derived from the hindgut, which includes 1/3 distal transverse colon, descending colon, sigmoid colon, rectum, and anus above the pectinate line.
Supply of nerves
The enteric nervous system comprises about a hundred million neurons embedded in the peritoneum, the lining of the gastrointestinal tract extending from the esophagus to the anus. These neurons are collected into two myenteric plexuses (or Auerbach) located between the longitudinal and fine muscle layers, and the submucosal (or Meissner) plexus that lies between layers of smooth muscle and circular mucosa.
The parasympathetic innervation to the ascending colon is supplied by the vagus nerve. The sympathetic innervation is supplied by the splanchnic nerve that joins the celiac ganglia. Most of the gastrointestinal tract is inserted by two large celiac ganglia, with the top of each ganglion joining the larger splanchnic nerve and the lower part joining the lower splanchnic nerve. From this ganglia many gastric plexus arise.
Development
At the beginning of embryonic development, the embryo has three layers of germs and is adjacent to the yolk sac. During the second week of development, the embryo grows and begins to surround and envelop some of this sac. The wrapped part forms the basis for the adult digestive tract. Parts of this foregut begin to differentiate into gastrointestinal organs, such as the esophagus, stomach, and intestines.
During the fourth week of development, the stomach rotates. The abdomen, originally located at the midline of the embryo, rotates so that its body is on the left. This rotation also affects part of the gastrointestinal tube just below the stomach, which will continue to be duodenum. At the end of the fourth week, the growing duodenum begins spitting out a small outpouch on its right side, the liver diverticulum, which will continue to be a biliary tree. Right below is the second outpouching, known as cystic diverticulum , which will eventually develop into the gall bladder.
Clinical interests
Every part of the digestive system is subject to many disorders that can be innate. Oral diseases can also be caused by pathogenic bacteria, viruses, fungi and as a side effect of some medications. Mouth disease includes tongue disease and salivary gland disease. A common gum disease in the mouth is gingivitis caused by bacteria in plaque. The most common viral infection in the mouth is gingivostomatitis caused by herpes simplex. Common fungal infections are candidiasis commonly known as thrush which affects the mucous membranes of the mouth.
There are a number of esophageal diseases such as the development of the Schatzki ring which can limit the entrance, causing swallowing difficulties. They can also completely block the esophagus.
Abdominal disease is often a chronic condition and includes gastroparesis, gastritis, and peptic ulcers.
A number of problems including malnutrition and anemia may arise from malabsorption, abnormal absorption of nutrients in the gastrointestinal tract. Malabsorption can have many causes ranging from infection, lack of enzymes such as pancreatic exocrine insufficiency. It can also arise as a result of other digestive diseases such as celiac disease. Celiac disease is an autoimmune disorder of the small intestine. This can lead to vitamin deficiency because of improper absorption of nutrients in the small intestine. The small intestine can also be blocked by the volvulus, the intestinal windings that become wrapped around the mesentery. This can cause mesenteric ischemia if it is severe enough.
Common bowel disorders are diverticulitis. Diverticula is a small pouch that can form inside the intestinal wall, which can become inflamed to give diverticulitis. The disease can have complications if an inflamed diverticulum erupts and sets incoming infections. Any infection can spread further into the lining of the abdomen (peritoneum) and cause potentially fatal peritonitis.
Crohn's disease is a common chronic inflammatory bowel disease (IBD), which can affect any part of the GI tract, but mostly begins in the ileal terminal.
Ulcerative colitis in the form of ulcerative colitis, is another inflammatory bowel disease limited to colon and rectum. Both IBDs may provide an increased risk of developing colorectal cancer. Ulcerative coliltis is the most common of IBD
Iritable bowel syndrome (IBS) is the most common functional gastrointestinal disorder. This is an idiopathic disorder that has been defined by the Roman process.
Giardiasis is a small intestinal disease caused by parasite protista Giardia lamblia . It does not spread but remains limited to the lumen of the small intestine. Often asymptomatic, but often can be indicated by various symptoms. Giardiasis is the most common pathogenic parasitic infection in humans.
There are diagnostic tools that mostly involve the consumption of barium sulfate to investigate gastrointestinal disorders. This is known as the upper gastrointestinal series that enables pharyngeal, laryngeal, esophageal, stomach and small intestine and lower gastrointestinal series for imaging of the colon.
In pregnancy
Gestation may predispose to certain digestive disorders. Gestational diabetes can develop in the mother as a result of pregnancy and while it is often present with few symptoms, it can cause pre-eclampsia.
See also
- Gastrointestinal physiology
- Brainstem axis
- Neurogastroenterology
References
Source of the article : Wikipedia
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