Urinary System Notes

Urinary System Overview

  • Organs:
    • Kidneys: Produce urine
    • Urinary tract: Eliminates urine
    • Ureters: Paired tubes
    • Urinary Bladder: Muscular sac
    • Urethra: Exit tube
  • Urination (Micturition): Process of urine elimination through bladder contraction.

Functions of the Urinary System

  • Excretion: Removal of organic wastes from body fluids.
  • Homeostatic Regulation:
    • Maintains blood plasma volume and solute concentration.
  • Elimination: Discharge of waste products.

Homeostatic Functions

  1. Regulates Blood Volume and BP:
    • Adjusts water volume in urine
    • Releases erythropoietin and renin.
  2. Ion Regulation:
    • Controls sodium, potassium, chloride, and calcium ions in urine.
  3. Blood pH Stabilization:
    • Regulates hydrogen and bicarbonate ion loss in urine.
  4. Nutrient Conservation:
    • Prevents valuable nutrients from being excreted.
  5. Detoxification Aid:
    • Assists liver in detoxifying poisons.

The Kidneys

  • Position:
    • Maintained by renal fascia and protected by fibrous capsule.
  • Blood Supply:
    • Receives 20-25% of cardiac output (1200 mL/min).

Nephron Structures

  • Types of Nephrons:
    • Cortical Nephrons (85%): Located in the cortex; short nephron loops.
    • Juxtamedullary Nephrons (15%): Extend deep into medulla; involved in concentration of urine.
  • Nephron Components:
    1. Renal Corpuscle: Includes glomerulus and Bowman's capsule
    2. Renal Tubule: Comprises PCT, nephron loop, DCT.

Filtration and Reabsorption

  • Filtration at Glomerulus:
    • Blood pressure forces water and solutes into capsular space, forming filtrate.
    • Larger solutes (e.g., proteins) are retained in blood.
  • Reabsorption:
    • Nutrients and water reabsorbed primarily in proximal convoluted tubule.

Kidney Diseases

  • Chronic Kidney Disease (CKD):
    • High BP damages glomeruli; leads to decreased kidney function.
  • Nephrolithiasis:
    • Kidney stones formed from crystallized minerals; treatment includes hydration or procedures.
  • Glomerulonephritis:
    • Inflammation of glomeruli; usually resolves with treatment.
  • Polycystic Kidney Disease (PKD):
    • Genetic disorder causing fluid-filled cysts; may require transplant.
  • Urinary Tract Infection (UTI):
    • Bacterial infection in urinary system; complications can arise if kidneys are infected.