Lecture Notes on Urinary System

Introduction to Urination

• Known as micturition by anatomists, but commonly referred to as urination.
• Purpose: Remove toxins and maintain water-volume homeostasis.
• Unique to humans: Study of urine as diagnostic tool.

Historical Perspective

• Early Sumerian, Babylonian, and medieval physicians used urine for diagnosis.
• Modern tests detect ailments based on urine's color, smell, clarity, and chemical composition.

Composition of Urine

• 95% water, slightly acidic (pH ~6), aromatic.
• Contains over 3000 chemical compounds.
• Diagnostic clues:
  • Cloudy urine: Possible urinary tract infection.
  • Sweet smell: Possible diabetes.
  • Pink urine: Potential internal bleeding.
  • High protein levels: Possible pregnancy, excessive exercise, high blood pressure, or heart failure.

Urinary Production Regulation

• Blood volume and pressure influence urine production through glomerular filtration.
• Glomerular filtration rate: Blood flow through glomeruli per minute.
  • Kidneys maintain constant flow rate despite blood pressure changes via autoregulation.

Hormonal Influence

• Caffeine and alcohol inhibit antidiuretic hormone (ADH), affecting urine production and hydration.
• ADH function:
  • Facilitates water reabsorption through aquaporins in nephron tubules.

Urine Transport and Storage

• Ureters transport urine using peristalsis to the bladder.
  • Bladder anatomy: Inner mucosa, detrusor muscle, protective outer membrane.
  • Bladder capacity: Comfortably holds ~500 ml, maximum ~1 liter.

Urination Control

• Internal Sphincter: Involuntary control via autonomic nervous system.
• External Sphincter: Voluntary control via skeletal muscle.
• Stretch receptors in bladder wall signal need to urinate.
• Brainstem (pons) regulates urination:
  • Pontine Storage Area: Inhibits urination.
  • Pontine Micturition Center: Initiates urination.

Conclusion

• Summary of urine regulation and elimination processes.
• Acknowledgement of contributors and support for the educational platform.