Mechanisms which regulate bile secretion act to either alter secretion rate, or contract the gall bladder. The primary regulator of bile acid production is the concentration of bile acids in the portal blood. Elevated blood bile feedsback to inhibit the enzyme cholesterol 7-hydroxylase which is required for the synthesis of primary bile acids. Therefore, when bile concentration in portal blood is high, bile synthesis is inhibited and secretion is stimulated thereby facilitating the entero-hepatic circulation of bile. As bile concentration in the blood decreases following a meal, synthesis is initiated by removing inhibition of cholesterol 7-hydroxylase.
Obstructions lead to buildup of bilirubin in the blood causing symptomatic jaundice.
Bile salts which remain in the colon act both as an osmotic agent and also as a secretory stimulant. Bile salts in the portal blood cause increased secretion of bile salts by hepatocytes, and inhibition of de novo synthesis of bile. Brunner's glands - mucous and HCO3 secreting glands which are found in the upper duodenum between the sphincter of Oddi and the pyloric sphincter. Intestinal Villi - Refers to the extensive folding observed in the surface of the intestine, covered with transporting epithelial cells. Crypts of Lieberkuhn - Pits found in all parts of the small intestine.