Bile Cholecystokinin

Bile is secreted by the liver, stored in the gallbladder, and used in the small intestine. It is transported toward the small intestine by the hepatic duct (from the liver) and the cystic duct (from the gallbladder), which join to form the common bile duct. Pancreatic juice is transported toward the small intestine by the pancreatic duct. The common bile duct and the pancreatic duct join to form the hepatopancreatic ampulla, which empties into the duodenum. The entrance to the duodenum is surrounded by the Sphincter of Oddi. This sphincter is closed between meals in order to prevent bile and pancreatic juice from entering the small intestine it relaxes in response to the intestinal hormone cholecystokinin, thus allowing biliary and pancreatic secretions to flow into the duodenum. 

CCK-PZ 50 113-116), whose C-terminal pentapeptide sequence is identical with that of gastrin, is discharged into the blood from certain intestinal cells and reaches the gallbladder, where it causes the bile to discharge into the intestine, thus promoting digestion. Cholecystokinin also functions as a cerebral neurotransmitter. 

In addition to growth factors, it has been shown that countless other molecules have multiple functions. Cholecystokinin, for example, is a peptide that acts as a hormone in the intestine, where it increases the bile flow during digestion, whereas in the nervous system it behaves as a neurotransmitter. Encephalins are sedatives in the brain, but in the digestive system are hormones that control the mechanical movements of food. Insulin is universally known for lowering the sugar levels in the blood, but it also controls fat metabolism and in other less known ways it affects almost every cell of the body. 

There are a variety of peptide hormones acting in the gut the gastrins stimulate gastric acid secretion secretin and somatostatin inhibit the production of gastrins. Cholecystokinin and somatostatin can inhibit gastric acid secretion directly, and the former one causes the gall-bladder to contract and thus force bile into the duodenum. 

The flow of bile is lowest during fasting, mostly being diverted to the gall bladder for concentrating. When chyme from an ingested meal enters the small intestine, acid and partially digested fats and proteins stimulate secretion of the enteric hormones cholecystokinin and secretin. 

Cholecystokinin (cholecysto = gall bladder and kinin = movement) release is stimulated by the presence of fat in the duodenum it induces contractions of the gall bladder and common bile duct, resulting in delivery of bile into the gut. 

Bile, pH 7.8-8.6, is produced continuously in humans. Hepatic bile is concentrated and stored in the gall bladder between meals. It is ejected from the gall bladder and flows into the duodenum when food enters the intestine. The main constituents of bile are bile salts, bilirubin, end products of hemoglobin breakdown, the electrolytes sodium, chloride, and bicarbonate, cholesterol, phospholipids, and lecithin. The gall bladder contracts within 30 min after eating due to liberation of cholecystokinin. The most effective stimulus to this is food high in fat. 

The chemical phase of digestion also involves the hormone cholecystokinin (CCK). Dietary fats and proteins elicit the release of CCK from cells of the intestines. The versatility of this hormone in digestion is revealed, later in this chapter, via studies involving dogs, rats, and humans. These studies address the influence of CCK on the release of pancreatic enzymes, bile salts, and pancreatic bicarbonate into the lumen of the small intestines. 

The duodenum is the shortest part of the small intestine, where most chemical digestion occurs. The duodenum releases secretin, a hormone, which suppresses gastric acid. Cholecystokinin, a hormone, is released by the duodenum that simulates flow of bile from the gallbladder into the duodenum. Bile (produced by the liver), trypsin, chymotrypsin, lipase, and amylase (all produced by the pancreas) digest carbohydrates, protein, and fat in preparation for absorption in the small intestine. The duodenum connects the stomach to the jejunum. The jejunum is the second division of the small intestine and connects the duodenum to the ileum. The ileum is the end of the small intestine. 

In response to a meal, cholecystokinin is released from the intestine and causes relaxation of the sphincter of Oddi and contraction of the gallbladder (see Chapter 48). This allows a concentrated solution of micelles (consisting of bile salts, lecithin, and cholesterol) to enter the intestine. In the intestinal lumen, dietary cholesterol and the products of triglyceride digestion (predominantly free fatty acids and monoglycerides) are incorporated into mixed micelles. Micelles deliver lipolytic products to the mucosal surface. To carry out these functions, a critical micellar bile acid concentration of 2ramoI/L is necessary. 

Cholecystokinin (CCK) is a 33 amino acid gastrointestinal peptide hormone of that was originally isolated from porcine gut and was given its name "the gallbladder mover" due to its ability to stimulate bile flow [1],... 

Cholecystokinin Stimulates secretion of digestive enzymes and bile... 

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