Key Concepts and Functions of the Liver and Pancreas

Anatomy and Function of the Digestive System

• Digestive Tract Components:

  • Oral Cavity: Swallowing and chewing (minimal digestion)

  • Esophagus: Transport food via peristalsis

  • Stomach:

    • Motility: Peristaltic mixing, propulsion

    • Secretion: Hydrochloric acid (HCl), pepsinogen, gastric lipase, and mucus

    • Digestion: Proteins, fats

    • Absorption: Lipid-soluble substances (e.g., alcohol, aspirin)

  • Small Intestine:

    • Motility: Segmentation mixing and propulsion

    • Secretion: Bile, enzymes from pancreas, mucus, hormones (e.g., CCK, secretin)

    • Digestion: Carbohydrates, fats, polypeptides, nucleic acids

    • Absorption: Peptides, amino acids, glucose, fructose, fats (diffusion)

  • Large Intestine:

    • Motility: Segmental mixing, mass movement

    • Secretion: Mucus

    • Absorption: Ions, water, minerals, vitamins from bacteria

The Liver

• General Characteristics:

  • Largest internal organ, average weight 1.2-1.5 kg

• Functions:

  • Detoxification: Conversion of toxic substances into less toxic substances (e.g., urea)

  • Carbohydrate Metabolism: Converts glucose to glycogen; gluconeogenesis

  • Lipid Metabolism: Produces triglycerides and cholesterol

  • Protein Synthesis: Produces essential proteins including albumin and clotting factors

  • Bile Secretion: Critical for digestion, composed of bile salts, bilirubin, and cholesterol

    • Bile Salts: Emulsifies fats in small intestine

    • Bilirubin: Pigment resulting from red blood cell breakdown

    • Important for digestion and absorption of dietary fats.

Anatomy of the Liver

• Hepatic Portal Circulation:

  • Receives blood from the gastrointestinal tract via the hepatic portal vein

  • Excretes bile salts and bilirubin into the duodenum

• Hepatocytes: Main functional cells organized into lobules essential for bile production

Liver Diseases and Damage

• Common Sources:

  • Toxins: E.g., paracetamol, alcohol, wild mushrooms

  • Infections: Hepatitis A, B, C (leading to chronic inflammation and cancer)

  • Fatty Liver Diseases: Non-alcoholic fatty liver disease (NAFLD) associated with obesity and metabolic diseases

  • Jaundice: Caused by excessive bilirubin, leading to yellowing of skin/eyes

The Pancreas

• General Characteristics:

  • Weighs between 40-180 g (average ~90 g)

  • Exocrine Function: Secretes digestive enzymes and sodium bicarbonate

  • Endocrine Function: Hormones like insulin and glucagon from pancreatic islet cells

Function of the Pancreas

• Digestive Enzyme Secretion: Includes amylase, lipase, and proteases (20 types in total)

• Hormonal Regulation:

  • Insulin: Lowers blood glucose by promoting uptake into cells (produced by beta cells)

  • Glucagon: Raises blood glucose by stimulating liver glycogen breakdown (produced by alpha cells)

Diseases of the Pancreas

• Diabetes Mellitus: Type 1 diabetes (autoimmune destruction of beta cells), leads to high glucose levels

• Pancreatitis: Inflammation of pancreas due to gallstones, alcohol abuse; can be acute or chronic, leading to tissue damage and scarring

Summary of Digestive Processes

• Role of bile in emulsifying fats, facilitating absorption of fat-soluble vitamins and fat digestion.

• Interaction and balance between liver and pancreas essential for overall digestive health and metabolic function.