urinary system

• Components of the urinary system

  • Kidneys
  • Ureters
  • Urinary bladder
  • Urethra
• Functions of the urinary system


  • Remove metabolic wastes and excess substances
  • Regulate composition, pH, and volume of body fluids
  • Control red blood cell production, blood pressure, and calcium ion absorption
• Kidney


  • Bean-shaped, about 12 cm long, 6 cm wide, 3 cm thick, enclosed in a fibrous capsule
• Functions of the kidneys

  • Filter waste from the blood and produce urine
  • Regulate body fluid volume, composition, and pH
  • Remove nitrogenous and sulfur-containing waste products
  • Produce erythropoietin (EPO) to regulate red blood cell production
• Components of the nephron

  • Renal corpuscle (glomerulus, glomerular capsule)
  • Proximal convoluted tubule (PCT)
  • Nephron loop (loop of Henle)
  • Distal convoluted tubule (DCT)
• Functions of the nephron

  • Filtration, reabsorption, and secretion to form urine
• Urine formation


  1. Glomerular Filtration: Plasma filters through glomerular capillaries into Bowman's capsule

  2. Tubular Reabsorption: Substances move from tubules into peritubular capillaries

  3. Tubular Secretion: Substances move from capillaries into tubules
• Hormones regulating urine concentration and volume

  • Aldosterone and ANP: Affect solute concentration, especially sodium
  • ADH: Increases water reabsorption, concentrates urine
• Countercurrent mechanism


  Mechanism in nephron loops and vasa recta that regulates urine concentration and volume
• Components of the urinary tract

  • Ureters
  • Bladder
  • Urethra
• Micturition


  Involves stretch receptors in the bladder, detrusor muscle contractions, and control by the brainstem and cerebral cortex
• Developmental abnormalities of the urinary system

  • Crossed fused ectopia
  • Horseshoe kidney
  • Nephrotic syndrome
  • Polycystic kidney disease
• Age-related changes in the urinary system

  • Slower removal of wastes
  • Kidney shrinkage
  • Loss of elasticity in the urinary tract
  • By age 80, the kidneys lose about one-third of their mass