BILIARY PHYSIOLOGY
The gallbladder stores and concentrates bile (10 times) until it is required in the small intestine. During the process of concentration, water and ions are absorbed through the lining of the gallbladder.
When the small bowel needs bile, the smooth muscle wall of the gallbladder to contract and push the bile into the cystic duct, common bile duct and small intestine.
When the small intestine is empty, a valve located around the bulb hepato-pancreatic sphincter called the bulb hepato-pancreatic (sphincter of Oddi) closes and causes the bile accumulated up to the cystic duct gallbladder to be stored [29].
Bile
Liver cells secrete daily from 800 to 1000 ml of bile, yellow liquid, brownish or olive-green, its pH is between 7.6 and 8.6.
Bile is composed primarily of water and bile acids, bile salts, cholesterol, phospholipids called lecithin, bile pigments and various ions. Bile is both a product of excretion and intestinal secretion.
Bile is secreted continuously by the liver, then stored in the gallbladder, which concentrated.At the time of digestion, bile is sent by the gallbladder into the duodenum through the bile duct.
Its role is to promote the absorption of fat by bile salts it contains. It still consists of water, mucin, minerals, pigments from the breakdown of hemoglobin and cholesterol.
Bile salts
Bile salts, which are salts of sodium and potassium of bile acids (mainly cholic and chenodeoxycholic acid) play a role in the emulsification, the degradation of large globules of fat into a suspension of fine droplets fat and fat absorption after digestion.
The fine droplets of fat have a very large surface area for the action of pancreatic lipase necessary for a rapid digestion of fats. Cholesterol is rendered soluble in bile by bile salts and lecithin.
The main bile pigment is bilirubin. When red blood cells break down, iron, hemoglobin and bilirubin (derived from the heme) are released. Iron and globin are recycled, but some of the bilirubin is excreted in the bile ducts. Bilirubin is then degraded in the gut. One of its degradation products, urobilinogen, gives feces their normal brown color.
Bile salts are molecules of steroidal structure synthesized by hepatocytes at the expense of cholesterol under control of a single enzyme: cholesterol - 7 - hydrolase.
In normal humans, the major bile acids, cholic acid and chénodeoxycholique are combined with two amino acids glycine and taurine.As conjugates, bile salts are secreted into bile by hepatocytes cells.
The regulation of bile secretion
Bile secretion is regulated by nervous and hormonal factors. Vagal stimulation of the liver may increase more than twice the normal rate of production of bile. Secretin, a hormone that stimulates the production of pancreatic juice rich in bicarbonate ions (HCO3-), also stimulates the secretion of HCO3-rich bile by the liver cells.
The increased blood flow in the liver leads to a certain point,increasing bile secretion.
Finally, the presence of a large amount of bile salts in the blood also increases the rate of production of bile.
Cholecystokinin (CCK), a hormone that stimulates the production of pancreatic juice rich in digestive enzymes, also stimulates contraction of the gallbladder. Thus compressed the bile passes from the gallbladder to the bile duct.
In addition, cholecystokinin causes relaxation of the sphincter of the ampulla of Vater hepato-pancreatic, thus promoting the flow of bile into the duodenum.
When the small bowel needs bile, the smooth muscle wall of the gallbladder to contract and push the bile into the cystic duct, common bile duct and small intestine.
When the small intestine is empty, a valve located around the bulb hepato-pancreatic sphincter called the bulb hepato-pancreatic (sphincter of Oddi) closes and causes the bile accumulated up to the cystic duct gallbladder to be stored [29].
Bile
Liver cells secrete daily from 800 to 1000 ml of bile, yellow liquid, brownish or olive-green, its pH is between 7.6 and 8.6.
Bile is composed primarily of water and bile acids, bile salts, cholesterol, phospholipids called lecithin, bile pigments and various ions. Bile is both a product of excretion and intestinal secretion.
Bile is secreted continuously by the liver, then stored in the gallbladder, which concentrated.At the time of digestion, bile is sent by the gallbladder into the duodenum through the bile duct.
Its role is to promote the absorption of fat by bile salts it contains. It still consists of water, mucin, minerals, pigments from the breakdown of hemoglobin and cholesterol.
Bile salts
Bile salts, which are salts of sodium and potassium of bile acids (mainly cholic and chenodeoxycholic acid) play a role in the emulsification, the degradation of large globules of fat into a suspension of fine droplets fat and fat absorption after digestion.
The fine droplets of fat have a very large surface area for the action of pancreatic lipase necessary for a rapid digestion of fats. Cholesterol is rendered soluble in bile by bile salts and lecithin.
The main bile pigment is bilirubin. When red blood cells break down, iron, hemoglobin and bilirubin (derived from the heme) are released. Iron and globin are recycled, but some of the bilirubin is excreted in the bile ducts. Bilirubin is then degraded in the gut. One of its degradation products, urobilinogen, gives feces their normal brown color.
Bile salts are molecules of steroidal structure synthesized by hepatocytes at the expense of cholesterol under control of a single enzyme: cholesterol - 7 - hydrolase.
In normal humans, the major bile acids, cholic acid and chénodeoxycholique are combined with two amino acids glycine and taurine.As conjugates, bile salts are secreted into bile by hepatocytes cells.
The regulation of bile secretion
Bile secretion is regulated by nervous and hormonal factors. Vagal stimulation of the liver may increase more than twice the normal rate of production of bile. Secretin, a hormone that stimulates the production of pancreatic juice rich in bicarbonate ions (HCO3-), also stimulates the secretion of HCO3-rich bile by the liver cells.
The increased blood flow in the liver leads to a certain point,increasing bile secretion.
Finally, the presence of a large amount of bile salts in the blood also increases the rate of production of bile.
Cholecystokinin (CCK), a hormone that stimulates the production of pancreatic juice rich in digestive enzymes, also stimulates contraction of the gallbladder. Thus compressed the bile passes from the gallbladder to the bile duct.
In addition, cholecystokinin causes relaxation of the sphincter of the ampulla of Vater hepato-pancreatic, thus promoting the flow of bile into the duodenum.
08:29
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