Lecture 1: Introduction to the Urinary System and Its Anatomy

Overview of the Urinary System

• Composed of:
  • Two kidneys
  • Two ureters
  • One urinary bladder
  • One urethra
• Function:
  • Filters blood and removes waste (mostly metabolic)
  • Returns most water and solutes to the bloodstream

Medical Disciplines

• Nephrology: Studies the function and diseases of the urinary and male reproductive systems
• Urology: Surgical branch related to the urinary and male reproductive systems

Anatomy Details

• Kidneys:
  • Right kidney is positioned lower than the left due to liver displacement
  • Located in the posterior part of the perianal cavity (retroperitoneal)
  • Sit against floating ribs for protection
  • Surrounded by three layers:
    • Renal capsule
    • Adipose capsule (fat layer)
    • Renal fascia
• Ureters:
  • Connect kidneys to the urinary bladder
  • Located retroperitoneally, passing by the iliac crest
• Urinary Bladder:
  • Sits behind the pubic symphysis
• Urethra:
  • In women: releases urine
  • In men: releases urine and transports semen

Functions of the Urinary System

• Regulates blood volume and composition
  • Filters and adjusts water content, producing either dilute or concentrated urine
  • Regulates blood ions and pH levels
  • Secretes renin for blood pressure regulation
  • Releases hormones:
    • Erythropoietin (stimulates red blood cell production)
    • Calcitriol (active Vitamin D)
• Detoxifies and excretes waste
  • Works with the liver for detoxification

External Anatomy of the Kidney

• Size and Location:
  • Kidney-shaped, about 4-5 inches long, 2-3 inches wide
  • Located just above the waist, between the peritoneum and posterior abdominal wall
  • Protected by the 11th and 12th ribs (floating ribs)
• Layers Around the Kidney:
  • Renal Capsule: Innermost layer
  • Adipose Capsule: Middle fat layer
  • Renal Fascia: Outermost connective tissue

Additional Points

• Kidneys have one opening (hilus) where blood vessels, lymphatics, and nerves enter/exit
• Excessively thin individuals may have mobile kidneys, leading to potential ureter kinking and urine flow obstruction
• Transverse section illustrations show the positioning of kidneys relative to the liver and other organs

This lecture provides a foundational understanding of the urinary system's anatomy, functions, and related medical disciplines, with a focus on the kidneys' role in maintaining homeostasis.