GALLBLADDER | GIT | ROLE COMPOSITIOnstructure | function | | BSN | MLT | DENTAL RADIOLOGY|LECTURE 8 скачать в хорошем качестве

GALLBLADDER | GIT | ROLE COMPOSITIOnstructure | function | | BSN | MLT | DENTAL RADIOLOGY|LECTURE 8

GALLBLADDER | GIT | ROLE COMPOSITIOnstructure | function | | BSN | MLT | DENTAL RADIOLOGY|LECTURE 8 The gallbladder (gall-bile) is a pear-shaped sac that is located in a depression of the posterior surface of the liver. ▶ It is 7–10 cm (3–4 inches) long and typically hangs from the anterior inferio margin of the liver. ▶ It has a fundus or expanded end, a body or main part and a neck, which is continuous with the cystic duct. ▶ The wall of the gall bladder has the same layers of tissue as those described in the basic structure of the alimentary canal, with some modifications. 1. Mucosa: Innermost layer, secretes mucus 2. Submucosa: Connective tissue layer 3. Muscularis: Smooth muscle layer for contraction 4. Serosa: Outermost layer Each day, hepatocytes secrete 800–1000 mL of bile, a yellow, brownish, or olive-green liquid. ▶ It has a pH of 7.6–8.6 and consists mostly of water, bile salts, cholesterol, a phospholipid called lecithin, bile pigments, and several ions. ▶ The principal bile pigment is bilirubin. ▶ The phagocytosis of aged red blood cells liberates iron, globin, and bilirubin (derived from heam). ▶ The iron and globin are recycled, the bilirubin is secreted into the bile and is eventually broken down in the intestine. One of its breakdown products—stercobilin—gives feces their normal brown color. Bile is partially an excretory product and partially a digestive secretion. ▶ Bile salts, which are sodium salts and potassium salts of bile acids (mostly chenodeoxycholic acid and cholic acid), play a role in emulsification, the breakdown of large lipid globules into a suspension of small lipid globules. ▶ The small lipid globules present a very large surface area that allows pancreatic lipase to more rapidly accomplish digestion of triglycerides. ▶ Bile salts also aid in the absorption of lipids following their Digestion