Urinary System Lecture Notes

Overview

• Micturition is the anatomical term for urination.
• Urination is essential for removing toxins and maintaining blood pressure.
• Humans study urine to diagnose various ailments.
• Urological tests analyze color, smell, clarity, and chemical composition.

Historical Perspective

• Ancient physicians used urine for diagnostic purposes.
• Urine as a diagnostic tool dates back to early Sumerian and Babylonian physicians.
• Medieval doctors often diagnosed diseases based on urine analysis.

Composition of Urine

• Fresh urine is ~95% water, slightly acidic (pH ~6), and varies in color based on hydration.
• Contains over 3000 chemical compounds.
• Cloudiness, sweetness, and color can indicate various health conditions:
  • Cloudy urine with white blood cells indicates a urinary tract infection.
  • Sweet-smelling urine with glucose suggests diabetes.
  • Pink urine (without dietary causes) could indicate internal bleeding.
  • High protein levels could indicate pregnancy, high blood pressure, heart failure, or excessive exercise.

Urine Production Regulation

• Glomerular Filtration begins with filtering blood in glomeruli.
• Glomerular Filtration Rate (GFR): Regulates blood flow in glomeruli.
• Intrinsic regulation helps maintain a constant filtration rate despite blood pressure changes.
• Hormonal Influence:
  • Caffeine & alcohol inhibit Antidiuretic Hormone (ADH), affecting water reabsorption.
  • ADH normally helps retain water by moving aquaporins to cell membranes.

Urine Storage and Excretion

• Ureters: Move urine to the bladder using peristalsis.
• Bladder: A collapsible sac with three layers - inner mucosa, muscular layer (detrusor), and an outer membrane.
  • Expands to hold up to 1 liter of urine.
  • Overdistention can theoretically lead to a burst bladder.
• Urethra: Passes urine through internal and external sphincters.
  • Internal urethral sphincter: Autonomically controlled.
  • External urethral sphincter: Voluntarily controlled.

Nervous System's Role

• Stretch receptors in bladder wall trigger urination reflexes.
• Reflexive Urination: In infants, urination is a reflex without voluntary control.
• Brainstem Control:
  • Pontine storage area inhibits urination.
  • Pontine micturition center allows urination.
• Conscious control develops as the nervous system matures.

Summary

• The urinary system regulates urine production and excretion.
• GFR and hormones play crucial roles in urine concentration.
• Urine storage involves multiple anatomical structures and processes.
• The nervous system controls voluntary and reflexive urination.