Digestive system bile acids

Although products of fat digestion, including cholesterol, are absorbed in the first 100 cm of small intestine, the primary and secondary bile acids are absorbed almost exclusively in the ileum, and 98—99% are returned to the liver via the portal circulation. This is known as the enterohepatic circulation (Figure 26—6). However, lithocholic acid, because of its insolubility, is not reabsorbed to any significant extent. Only a small fraction of the bile salts escapes absorption and is therefore eliminated in the feces. Nonetheless, this represents a major pathway for the elimination of cholesterol. Each day the small pool of bile acids (about 3-5 g) is cycled through the intestine six to ten times and an amount of bile acid equivalent to that lost in the feces is synthesized from cholesterol, so that a pool of bile acids of constant size is maintained. This is accomplished by a system of feedback controls. 

Digestive system g agonists decrease secretion of stomach acid, reduce gastric motility, and prolong gastric emptying. Pancreatic, biliary, and intestinal secretions are reduced. Intestinal transit is also slowed. Peristaltic movements are reduced, but tone is increased, sometimes causing spasm. As a result, constipation is a frequent problem with opioid use. Bile duct pressure is also increased by opioids. 

N.A. Picrasma exeelsa (Sw.) Planch. Quassinoid (quassin), alkaloids, coumarin (scopoletin), vitamin B,.09 Strengthen digestive systems, increase bile flow, secretion of salivary juices, and stomach acid production. 

Electrophysiological studies of the smell and taste systems of fish have likewise demonstrated chemoreceptor cells that are responsive, with varying degrees of specificity, to the amino acids known to elicit feeding behavior.73 75 In addition, a number of fish have receptor cells that respond to bile acids, amphipathic steroid compounds that are used as digestive detergents and that can be released into the environment in substantial quantities. Responses can exhibit both exquisite specificity for the structure of a bile acid, and extreme sensitivity, as best exemplified by the sea lamprey.76 77... 

Bile salt molecules secreted by the gallbladder are essential for the emulsification and absorption of fats. They are the salt forms of bile acids, which are the major product of cholesterol catabolism in the liver. Bile salts form micelles as their hydrophobic face contacts the fat (triacylglycerol), and their polar face maintains contact with the aqueous enviromnent. This micelle formation allows water-soluble digestive enzymes to digest the entrapped triacylglycerol molecnle, releasing fatty acids that are readily absorbed by the digestive system. 

Bile Acids acids liberated by the gall bladder which play a role in the digestion of fats. Bilharzia parasitic disease due to schistosomes which live in the human circulatory system. Cholagogue substance which increases the flow of bile from the gallbladder. 

The liver secretes a elear, golden yellow viscous liquid known as bile . It is stored in gall bladder and is solely useful for the digestive system. It mainly consists of the inorganie ions like HCO3, Cl Na , K, etc., in addition to organic compoimds such as bile aeids, bile pigments, liquid fatty acids and cholesterol. Cholic Acid Deoxycholic Acid Chenodeoxycholic Acid. 

A detailed consideration of the behavior and solubility of lipolytic products in aqueous systems not containing bile acids has two justifications. First, digestion is an aqueous process and significant intestinal absorption of certain lipolytic products may occur in the absence of bile acids, despite their low solubility. It is a reasonable assumption that such absorption occurs from a molecular solution, or at lest a nonmicellar solution, and we therefore seek information on molecular solubility or types of aggregation or both in aque-our systems. Second, behavior of lipolytic products in the absence of bile acids provides a framework from which to predict the behavior of these compounds when bile acids are added. 

Figure 6. Because the solubility of cholesterol in aqueous systems is low, its absorption depends on the formation of detergent structures (mixed micelles) in the small intestine. Initially, when dietary fat enters the stomach and passes into the small intestine, it takes the form of relatively large lipid droplets (shown in grey). Bile acids (shown in black) reduce the surface tension in the hpid droplets, leading to the formation of smaller structures (mixed micelles). Mixed micelles consist of an outer sheU of bile acids, monoacylglycerols, phospholipids and lysolecithin, and an inner core of digestion products of fats such as fatty acids, monoacylglycerols, cholesterol (of which 90% infreeform), andfat-soluble micronutrients.

About 20% of the population of the United States has cholesterol levels that exceed the recommended total. Typical adults have about 150 g in their body and for a good reason—cholesterol is vital for the mnning of the body. It is an essential building block of cell membranes, especially of the nervous system, the brain, and the spinal cord. It is also a key chemical intermediate in the biological production of other steroids, especially the sex and the corticoid hormones, including cortisone. We need cholesterol to produce bile acids, which in turn are key chemicals that help digest the fats we consume, and we need it to form vitamin D, which enables us to utilize calcium in bone construction. 

Decahn ring systems appear as structural units m a large number of naturally occur ring substances particularly the steroids Cholic acid for example a steroid present m bile that promotes digestion incorporates as decahn and trans decahn units into a rather complex tetracyclic structure... 

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