Anatomy WK 10 (4/8) | Comprehensive Notes on Liver, Bile, and Kidney Functions

General Functions of the Liver

• Primary Role: Provides nutrition for the body by processing blood from intestines.
• Detoxification: Filters out harmful substances from blood before circulation.
• Nutrient Absorption: Absorbs proteins and sugars from digested food.

Hepatic Portal System

• Function: Network of veins transporting blood from the intestines to the liver.
• Structure: Comprised of portal veins and venous capillaries within the liver.

Hepatocytes

• Function: The primary functional cells of the liver.
  • Processes in Hepatocytes:
  • Glucose Storage: Converts excess glucose to glycogen.
  • Protein Synthesis: Modifies proteins for body use.
  • Bile Production: Secretes bile for fat digestion.
  • Detoxification: Produces enzymes to neutralize toxins.

Microscopic Liver Anatomy - Hepatic Lobule

• Structure: Hexagonal units in the liver containing:
  • Sinusoids: Capillaries facilitating blood flow to hepatocytes.
  • Portal Triad: Comprising three structures:
  • Portal Venule: Carries nutrient-rich blood from intestines.
  • Portal Arteriole: Supplies oxygen-rich blood to hepatocytes.
  • Bile Duct: Transports bile produced by hepatocytes.

Blood Flow Through the Liver

• Blood arrives via the portal vein, enters the portal venule, mixes in sinusoids, and exits through the central vein into the hepatic vein.

Bile Production and Transport

• Bile Composition: Essential for fat digestion; acts as a detergent to break down fat globules.
• Bile Canaliculi: Micro-tubes collecting bile from hepatocytes, leading to bile ducts and eventually out of the liver.
• Bile Ducts: Merge to form larger ducts that transport bile to the small intestines.

Liver Diseases

• Fatty Liver Disease:

  • Description: Excess fat storage in hepatocytes; often reversible with lifestyle changes.
  • Risks: High-fat diet or obesity can lead to liver dysfunction.

• Cirrhosis:

  • Description: Scar tissue replacing healthy liver tissue due to chronic inflammation.
  • Causes: Hepatitis, autoimmune diseases, alcohol abuse.
  • Consequences: Blood flow obstruction in the liver, leading to complications like ascites (fluid accumulation) and reduced liver function.

Ascites and Management

• Ascites: Caused by blocked flow in the liver leading to fluid leakage into the abdomen.
• Management: Manual drainage may be necessary, but the underlying problem must be addressed to prevent recurrence.

Biliary System

• Series of ducts connecting liver and gallbladder to the small intestine:
  • Right and Left Hepatic Ducts merge into the Common Hepatic Duct.
  • Cystic Duct: Connects gallbladder to the common hepatic duct for bile storage.
  • Common Bile Duct: Carries bile to the duodenum.

Gallstones

• Causes: Hardened bile formation due to genetic or dietary factors.
• Complications: Can block bile flow, leading to inflammation and risks of pancreatitis.
• Treatment: Gallbladder removal may be performed if gallstones are recurrent.

Pancreas Overview

• Structure: Composed of pancreatic islets (endocrine functions) and acinar cells (digestive functions).
• Duct System: Main pancreatic duct merges with the common bile duct, leading to the small intestine.

Kidney Function Overview

• Major Roles: Maintenance of blood volume and removal of waste products.
• Nephrons: Microscopic filtration units consisting of:
  • Cortical Nephrons mainly in the cortex.
  • Juxtamedullary Nephrons spanning cortex and medulla, possessing long loops of Henle.

Nephron Functioning

• Filtration: Occurs in glomeruli, collecting fluid into Bowman's capsule.
• Reabsorption: Fluid and electrolytes from tubules back to capillaries.
• Secretion: Removal of substances from capillaries into tubules.

Importance of Juxtaglomerular Apparatus

• Macula Densa: Senses urine concentration to regulate filtration and blood pressure via:
  • Mesangial cells: Constrict afferent or efferent arterioles based on urine concentration.
  • Granular cells: Release renin to raise blood pressure and reduce urine output in response to low blood volume.

Podocytes Function

• Prevent leakage except at filtration slits, regulating urine production based on hydration needs.

Diabetic Implications on Kidney Health

• Chronically high blood sugar causes glomerular inflammation, leading to excess filtration of proteins and glucose, indicating kidney dysfunction.