LIVER AND GALL BLADDER.pptx DIGESTIVE SYSTEM
- 1. Liver and gall bladder Vigneswaran Ganesan M.sc., Senior Lecturer Department of Biochemistry
- 2. SYNOPSIS
- 3. LIVER - largest gland in the body - weighs about 1.5kg in man - located in the upper and right side of the abdominal cavity immediately beneath the diaphragm FUNCTIONAL ANATOMY OF LIVER • Made up of hepatic lobes • Each lobe consists of many lobules called hepatic lobules Hepatic lobules FUNCTIONS Dual organ having both secretory and excretory function Structural & Functional unit of liver Honey comb like structure Made up of liver cells called HEPATOCYTES Arranged in hepatic plates Each plates made up of two columns of cells In between two columns of each plate lies a Bile canaliculus In between the neighboring plates, a blood space called sinusoid is present. Sinusoid is lined by the endothelial cells. In between the endothelial cells some special macrophages called Kupffer cells are present
- 4. PORTAL TRIADS • Each lobule is surrounded by many portal triads. Each portal triad consists of three vessels 1. A branch of hepatic artery. 2. A branch of portal vein. 3. A tributary of bile duct • The branches of hepatic artery and portal vein open into the sinusoid. • Sinusoid opens into the central vein. Central vein empties into hepatic vein. • Bile is secreted by hepatic cells and emp tied into bile canaliculus. From canaliculus, the bile enters the tributary of bile duct. • The tributaries of bile duct from canaliculi of neighboring lobules unite to form small bile ducts. • These small bile ducts join together and finally form left and right hepatic ducts which emerge out of liver
- 5. BILIARY SYSTEM • Biliary system is also known as extrahepatic biliary apparatus. • It is formed by gallbladder and the extrahepatic bile ducts (bile ducts outside the liver). • The right and left hepatic bile ducts which come out of liver join to form common hepatic duct. • It unites with the cystic duct from gallbladder to form common bile duct • The common bile duct unites with pancreatic duct to form the common hepatopancreatic duct or ampulla of Vater which opens into the duodenum. • There is a sphincter called sphincter of Oddi at the lower part of common bile duct, before it joins the pancreatic duct. It is formed by smooth muscle fibers of common bile duct. • It is normally kept closed; so the bile secreted from liver enters gall bladder where it is stored. • Upon appropriate stimulation the sphincter opens and allows flow of bile from gallbladder into the intestine
- 6. BLOOD SUPPLY TO LIVER
- 7. PROPERTIES AND COMPOSITION OF BILE Bile is a golden yellow or greenish fluid. It enters the digestive tract along with pancreatic juice through the common opening called ampulla of Vater. PROPERTIES Volume – 800 to 1200 mL/day Reaction – alkaline pH- 8 - 8.6 Specific gravity – 1.010 to 1.011
- 9. SECRETION AND STORAGE OF BILE Bile is secreted by hepatocytes. The initial bile secreted by hepatocytes contains large quantity of bile acids, bile pigments, cholesterol, lecithin and fatty acids. From hepatocytes, bile passes through canaliculi and hepatic ducts to reach common hepatic duct. From here it may enter the intestine or gallbladder. Sodium, bicarbonate and water are added to bile when it passes through the ducts. These substances are secreted by the epithelial cells of the ducts. The addition of sodium, bicarbonate and water increases the total quantity of bile When bile is stored in gallbladder, it undergoes many changes both in quality and quantity such as: 1. Volume is reduced because of absorption of large amount of water and electrolytes (except calcium and potassium). 2. Concentration of bile salts, bile pigments, cholesterol, fatty acids and lecithin is increased because of absorption of water. 3. The pH is slightly decreased. 4. Specific gravity is increased. 5. Mucin is added
- 11. BILE SALTS • Bile salts are the sodium and potassium salts of bile acids, which are conjugated with glycine or taurine. Bile salts are formed in liver FORMATION OF BILE SALTS • formed by primary bile acids Cholic acid deoxycholic acid Chenodeoxycholic acid lithocholic acid
- 12. FUNCTIONS OF BILE SALTS 1. Emulsification of fats 2. Absorption of fats 3. Choleretic action 4. Cholagogue action 5. Laxative action 6. Prevention of gall stone formation • Choleretic – bile salts stimulate the secretion of bile from liver. • Cholagogue - Cholagogue is an agent, which causes contraction of gallbladder (CCK) and release of bile into the intestine. • Laxative is an agent which induces defe cation. Bile salts act as laxatives by stimu lating peristaltic movements of the intestine
- 13. BILE PIGMENTS Bile pigments are the excretory products in bile. Bilirubin and biliverdin are the two bile pigments and bilirubin is the major bile pigment in human being. The bile pigments are formed during the breakdown of hemoglobin, which is released from the destroyed RBCs in the reticuloendothelial system
- 14. FORMATION AND EXCRETION OF BILE PIGMENTS
- 15. BILE FUNCTIONS 1. Digestive Function 2. Absorptive Function 3. Excretory Function 4. Laxative Action 5. Antiseptic Action 6. Choleretic Action 7. Maintenance Of PH In GIT 8. Prevention Of Gallstone Formation 9. Lubrication Function 10. Cholagogue Action
- 16. LIVER Liver is the largest gland and one of the vital organs of the body. It performs many vital metabolic and homeostatic functions FUNCTIONS 1. Metabolic function 2. Storage function 3. Synthetic function 4. Secretion of bile 5. Excretory function 6. Heat production 7. Hemopoietic function 8. Hemolytic function 9. Inactivation of hormones and drugs 10. Defensive and detoxification functions
- 17. GALL BLADDER Bile secreted from the liver is stored capacity 50mL (approx) not essential for life FUNCTIONS 1. Storage of bile 2. Concentration of bile 3. Alteration of pH of bile 4. Secretion of mucin 5. Maintenance of pressure in biliary system
- 18. REGULATION OF BILE SECRETION Bile secretion is a continuous process though the amount may be less during fasting. It starts increasing 3 hours after the meals. Secretion of bile from the liver and release of bile from the gallbladder are influenced by some chemical factors which are categorized into three groups: 1. Choleretics. 2. Cholagogue. 3. Hydrocholeretic agents
- 21. APPLIED PHYSIOLOGY • GALL STONES Gallstone is a solid crystal deposit that is formed by cholesterol, calcium ions and bile pigments in the gallbladder or bile duct. Cholelithiasis is the presence of gallstones in gallbladder. • FORMATION – Precipitates in the mucosa of gall bladder as a crystals. Bile pigments and calcium are attached to these crystals and results in gallstones. • Causes 1. Reduction in bile salts. 2. Excess of cholesterol or disturbed cholesterol metabolism 3. Excess of calcium ions due to increased concentration of bile. 4. Damage or infection of gallbladder epithelium. 5. Obstruction of bile flow from the gall bladder