Liver and Pancreas Anatomy and Function Notes

Largest Internal Organ

• Weighs approximately 1.5 kg or 2% of body weight

• Located in the right upper quadrant of the abdomen, beneath the diaphragm, and is protected by the rib cage

Main Functions:

• Bile Secretion: Aids in the digestion and absorption of fats and fat-soluble vitamins in the intestines.

• Synthesis and Endocrine Secretion: Produces major plasma proteins including:

  • Albumins: Maintain oncotic pressure and transport substances in the blood.

  • Fibrinogen: Plays a crucial role in blood clotting.

  • Apolipoproteins: Involved in lipid metabolism and transport.

  • Transferrin: Helps in the transport of iron throughout the body.

• Gluconeogenesis: Converts amino acids and other substrates into glucose to maintain blood sugar levels during fasting states.

• Detoxification: Breakdown and conjugation of ingested toxins and drugs, transforming them into less harmful substances for excretion.

• Amino Acid Deamination: Produces urea, which is subsequently removed from the blood by the kidneys.

Storage Functions:

• Glycogen: Stored as glycogen in granules for energy reserves.

• Triglycerides: Stored in lipid droplets and utilized during fasting for energy.

• Fat-Soluble Vitamins: Stores essential vitamins A, D, E, and K, contributing to various metabolic functions.

• Erythrocyte Removal: By Kupffer cells, which are specialized macrophages located within the liver, playing a key role in immune defense.

• Iron Storage: In complexes with ferritin, ensuring a readily available iron supply for erythropoiesis (red blood cell production).

Structural Organization of the Liver

• Glisson's Capsule: A fibrous connective tissue layer that surrounds the liver, providing structure and support.

• Hepatocytes:

  • Main functional cells of the liver performing essential functions such as:

  • Production of bile, plasma proteins, and amino acids.

  • Metabolism of fats, carbohydrates, and proteins.

  • Storage of glucose, vitamins, and iron.

  • Breakdown of metabolic waste products, drugs, and toxins, thereby sustaining homeostasis.

• Lobular Structure:

  • Hepatic Lobule: Basic structural unit of the liver, organized around a central vein and includes portal triads.

  • Portal Triad: Composed of:

  • Venule (portal vein): Carries nutrient-rich blood from the gastrointestinal tract.

  • Arteriole (hepatic artery): Supplies oxygen-rich blood to the liver.

  • Bile Ductule: Transports bile produced by hepatocytes to the bile ducts.

  • Sinusoids: Vascular channels between hepatocyte plates, facilitating blood flow and processing of nutrients and waste products.

Hepatic Sinusoids and Spaces

• Sinusoids:

  • Irregularly shaped vessels mixing venous and arterial blood, allowing for efficient exchange of substances.

  • Lined with fenestrated endothelium to enhance permeability.

• Space of Disse:

  • An area between sinoids and hepatocytes facilitating nutrient transfer and hepatic function modulation.

  • Houses stellate cells (involved in vitamin A storage and fibrosis) and Kupffer cells (immune response and phagocytosis).

Bile Production and Flow

• Bile Canaliculi:

  • Small channels between hepatocytes that collect bile for secretion.

  • Directly lead to bile ducts for transportation into the gallbladder or intestines.

• Bile Duct Structure:

  • Composed of:

  • Canal of Hering: Lined by cholangiocytes (bile duct epithelial cells), involved in bile modification.

  • Bile ductules that merge into larger interlobular bile ducts, facilitating bile transport.

Pancreas Overview

• Dual Role: The pancreas has both exocrine and endocrine functions critical for digestion and metabolic regulation.

• Exocrine Component:

  • Produces about 1.5 L of alkaline digestive enzymes daily, which play a key role in digestion.

  • Secreted from acinar cells into the small intestine to aid in nutrient breakdown.

• Endocrine Component:

  • Islets of Langerhans contain clusters of endocrine hormone-producing cells:

  • Alpha Cells: Produce glucagon, which raises blood sugar levels.

  • Beta Cells: Produce insulin, which lowers blood sugar levels.

  • Delta Cells: Secrete somatostatin, which regulates the endocrine system and slows down the digestive process.

Medical Applications

• Conditions related to the liver:

  • Acquired and hereditary diseases can affect liver function and structure.

  • Cholelithiasis: Formation of gallstones linked to water reabsorption and composition of bile, which can lead to complications if they block bile ducts.

  • Pancreatitis: A severe inflammation of the pancreas that can lead to severe complications when digestive enzymes activate prematurely within the pancreas, causing tissue damage.

  • Pancreatic Cancer: Often diagnosed late due to vague symptoms, leading to poor outcomes and limited treatment options.

• Risk Factors for Salivary Gland Disorders:

  • Xerostomia: Can involve viral infections, medications, dehydration, or radiation exposure.

  • Sialorrhea: Excess saliva production indicating underlying medical conditions such as neurological disorders or adverse medication effects.

Gall Bladder: A small organ located beneath the liver that stores and concentrates bile produced by the liver.

• Main Functions:

  • Storage: Stores bile that aids in fat digestion in response to meals.

  • Concentration: Absorbs water from bile to concentrate bile acids.

  • Release: Releases bile into the small intestine via the cystic duct during digestion, particularly after fatty meals.

• Structure:

  • Composed of three layers: mucosa, muscular layer, and serosa. Mucosa has folds to accommodate varying bile volumes.

  • Blood supply from the cystic artery, a branch of the hepatic artery.

• Clinical Significance:

  • Cholecystitis: Inflammation of the gallbladder often due to gallstones blocking the cystic duct.

  • Cholelithiasis: Formation of gallstones that can obstruct bile flow, potentially leading to pain and complications.

  • Function can be assessed via ultrasound or cholecystography to examine stones or inflammation.