Liver, Pancreas, and Gallbladder Function

Digestive System Overview

• Definition: A group of organs that convert food into energy and nutrients.

Accessory Organs of the Digestive System

• Key Organs:

  • Salivary Glands

  • Liver

  • Gall Bladder

  • Pancreas

Salivary Glands

• Major Salivary Glands: 3 pairs

  1. Parotid

  2. Submandibular

  3. Sublingual

• Minor Salivary Glands: Numerous microscopic glands throughout the oral mucosa.

• Functions:

  • Lubrication of ingested food and oral mucosa.

  • Enzymatic digestion of carbohydrates (CHO) and lipids via amylase and lipase.

Functions of the Liver

• Metabolism: Substances absorbed by the gut are processed by the liver before entering circulation.

  • Lipid metabolism: Involves cholesterol, triglycerides (TGs), phospholipids, vitamin A, and fatty acids.

  • Protein metabolism: Synthesis and degradation of amino acids and proteins; crucial products include albumin and clotting factors.

  • Carbohydrate metabolism: Formation, storage, and breakdown of glucose and glycogen.

• Bile Production: Emulsifies fats and facilitates absorption in the small intestine (SI).

• Blood Regulation: Phagocytosis of old or damaged red blood cells (RBCs), pathogens, and debris; metabolism of drugs and toxins.

Liver Structure

• Outer Layer: Surrounded by a thin fibrous capsule containing fibroblasts and collagenous fibers.

• Hepatocytes: The functional cells of hepatic parenchyma, arranged in lobules.

Hepatic Lobules

• Structure: Hexagonal or pentagonal, surrounded by reticular connective tissue (CT).

• Components Include:

  • Central vein in the middle.

  • Hepatocytes arranged in plates around the central vein.

  • Sinusoids interspersed between hepatocyte plates, facilitating nutrient absorption and secretion.

  • Blood supply from the hepatic portal vein and the hepatic artery flows into the sinusoids.

Portal Tract (Triad)

• Components:

  • Portal venule: Nutrient-rich but low in oxygen.

  • Hepatic arteriole: Oxygen supply.

  • Bile ducts: Drainage system for bile.

cell Types Found in Hepatic Lobules

1. Hepatocytes: Function as the main cell type with active involvement in metabolism and secrete bile.

2. Sinusoidal Endothelial Cells: Form the lining of the sinusoids, allowing exchange of substances.

3. Kupffer Cells: Specialized macrophages that perform phagocytic functions.

4. Ito Cells: Store vitamin A and can transform during liver injury.

Bile Canaliculi

• Function: Drain bile produced by hepatocytes; they transport bile from lobule centers to bile ducts.

• Structure: Formed by intracellular space between adjacent hepatocytes, leading to canals of Hering and bile ducts.

Biliary Tree

• Components: Right and left hepatic ducts, common hepatic duct, cystic duct (to the gallbladder), and common bile duct (to the duodenum).

Gallbladder

• Function and Structure: Stores bile (30-50 mL), contains a three-layer wall structure including mucosa, musculosa, and serosa; no muscularis mucosae.

• Mucosa Characteristics: Highly folded with simple columnar epithelium; functions in mucus secretion.

Definitions

• Cholelithiasis: Formation of gallstones.

• Cholecystitis: Inflammation of the gallbladder.

• Choledocholithiasis: Presence of stones in bile ducts.

• Cholangitis: Infection/inflammation of bile ducts.

Pancreas

• Structure: A mixed exocrine-endocrine gland located retroperitoneally.

• Exocrine Functions: Secretion of bicarbonate and digestive enzymes into the duodenum via ducts.

• Endocrine Functions: Secretion of insulin and glucagon by the Islets of Langerhans.

Islet of Langerhans

• Cell Types:

  • Alpha Cells: Produce glucagon.

  • Beta Cells: Produce insulin.

  • Delta Cells: Secrete somatostatin.

Pancreatic Carcinoma

• Characteristics: Most common pancreatic malignancy (85% of cases); risk factors include smoking and chronic pancreatitis.

• Clinical Signs: Jaundice, peripheral venous thrombosis, elevated serum markers (SPan-1, CA19-9).

Hepatic Disorders

• Cirrhosis: Chronic, irreversible liver disease characterized by widespread necrosis and fibrosis. Causes include chronic viral hepatitis and alcohol abuse.

  • Appearance: Nodular texture and fibrous tissue formation leading to dysfunctional liver architecture.

• Steatosis: Fatty liver condition marked by accumulation of fat within liver cells, can be macrovesicular or microvesicular.

Summary of Functions

• Liver: Processes nutrients, produces bile, regulates blood composition/volume, involved in detoxification.

• Gallbladder: Stores and concentrates bile.

• Pancreas: Secretes digestive enzymes and hormones that regulate blood sugar.