PP F

Overview of Liver and Biliary Systems

• The liver and biliary systems are integral to the digestive and circulatory systems.

• Important processes occur when food enters the small intestine and nutrients are absorbed by the intestinal walls.

• Nutrient-rich blood from the intestine enters the liver through the portal system, which plays a crucial role in metabolism and storage of these nutrients.

Portal Venous System

• Function: Transports nutrient-rich blood from the gastrointestinal (GI) tract (from lower esophagus to mid-anal canal) as well as from the spleen and pancreas to the liver.

• Blood Supply:

  • Supplied by the portal vein carrying blood from the GI tract.

  • Supplied by the hepatic artery providing oxygen-rich blood.

• Bile is drained from the liver through the biliary system, stored in the gallbladder, and transported via the common bile duct (CBD).

Anatomy of the Biliary System

• Key Structures:

  • Hepatic Ducts: Right and left hepatic ducts collect bile from the liver.

  • Cystic Duct: Connects the gallbladder to the hepatic duct.

  • Common Bile Duct: Formed by the merge of the cystic duct and common hepatic duct, carries bile to the small intestine.

  • Ampulla of Vater: Entry point of the bile into the small intestine (duodenum).

Microanatomy of Liver

• The liver is composed of cubical cells (hepatocytes) arranged in rows around a central vein.

• Sinusoids (blood vessels wider than capillaries) run alongside these cells, facilitating blood flow into the central vein.

Liver Functions

• Metabolism: Converting nutrients absorbed from food into energy and storage forms (like glycogen).

• Bile Production: Bile assists in breaking down fats for digestion.

• Detoxification: Clears blood of drugs, chemicals, and alcohol.

• Blood Clotting: Produces factors necessary for clotting; prothrombin is converted to thrombin.

• Immunity: Impacts overall immune function via its filtering capabilities.

Bile Composition and Function

• Bile is composed of water, bile salts, and cholesterol.

• Role: breaks down fats into finer particles for efficient digestion; aids in tracking fats in the digestive process.

• Gallstones: Formed from imbalances in the composition of bile, particularly excess cholesterol.

Anatomy and Function of the Gallbladder

• Storage: Gallbladder stores and concentrates bile when not in use; releases bile into the small intestine upon ingestion of food.

• Regulation: Controlled by the release of the enzyme cholecystokinin in response to fats and proteins entering the duodenum.

Pancreas Anatomy and Functions

• The pancreas functions as both an endocrine and exocrine gland:

  • Endocrine: Islets of Langerhans (small clusters of cells) produce insulin and glucagon for glucose regulation.

  • Exocrine: Acinar cells produce digestive enzymes (like amylase, lipase, trypsin) and bicarbonate that aids digestive processes.

Kidneys and Renal Function

• Structure: Bean-shaped organs located retroperitoneally, supplied by renal arteries with significant blood flow (25% of cardiac output).

• Nephron: Functional unit of kidneys, responsible for filtering blood and forming urine.

• Filtration: Glomerular filtration is the first step in urine formation, followed by selective reabsorption of vital nutrients and the secretion of waste products into urine.

Enzymes in Liver Functionality

• Amino Acids: Involved in protein synthesis; enzymes like AST and ALT are markers for liver health and disease diagnosis.

• Lactic Dehydrogenase: Indicates liver and other tissue health, with elevated levels suggesting various diseases or conditions.