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Study Guide: The Urinary System Overview

Mar 26, 2025

Anatomy Class: Chapter 24 - The Urinary System

Introduction

  • Lecture recorded exclusively for Dr. Young's anatomy class.
  • Focus on kidneys and urinary tract, which includes tubes leading from kidneys out of the body.

Functions of the Urinary System

  • Kidneys:
    • Primarily filters waste.
    • Maintains nutrients and water balance.
    • Regulates fluid balance and blood pressure.
    • Plays a role in acid-base balance by excreting or reabsorbing hydrogen ions.
  • Urinary Tract:
    • Composed of ureters, bladder, and urethra.
    • Bladder stores waste before removal from the body.

Kidney Function and Homeostasis

  • Maintains homeostasis by:
    • Removing metabolic waste.
    • Balancing electrolytes and fluids (osmolarity).
    • Managing acid-base balance.
    • Stimulating red blood cell production via the hormone erythropoietin.

Anatomy of the Kidneys

  • Location: Retroperitoneal (behind abdominal cavity tissue).
  • Surrounded by: Adipose tissue (fat) for protection.
  • Adrenal Glands: Sit atop kidneys, involved in endocrine functions.

Internal Structure of the Kidney

  • Renal Cortex: Outer region with a large blood supply.
  • Renal Medulla: Middle region with pyramids.
  • Renal Pelvis: Collects urine before it exits via ureters.
  • Nephrons: Functional unit, responsible for urine production.
    • Start in the cortex, go through pyramids.
    • Composed of renal corpuscle, proximal convoluted tubule, nephron loop, distal convoluted tubule, and collecting duct.

Blood Supply

  • Renal Arteries: Provide significant blood supply (1/4 of cardiac output).
  • Arterioles: Afferent (into) and efferent (out of) leading to/from glomerulus.

Nephron Functional Overview

  • Renal Corpuscle/Glomerulus: Filters blood, only part that acts as a filter.
  • Proximal Convoluted Tubule: Reabsorbs 60-70% of filtered materials.
  • Loop of Henle: Descending limb reabsorbs water, ascending reabsorbs sodium chloride.
  • Distal Convoluted Tubule: Fine-tunes reabsorption under hormonal control, manages acid-base balance.

Collecting Duct

  • Collects final urine product, can reabsorb water.
  • Leads to minor/major calyces, then renal pelvis.

Urinary Tract Components

  • Ureter: Transports urine from kidney to bladder.
  • Bladder: Muscular storage organ (detrusor muscle) that contracts to expel urine.
  • Trigone: Smooth area where ureters enter and urethra begins.

Urethra

  • Male vs. Female:
    • Male: Longer, passes through the prostate, dual function (urine and sperm).
    • Female: Shorter, higher UTI risk.

Micturition Reflex

  • Bladder fills, pressure increases, signals brain.
  • Internal sphincter closes, followed by external.
  • Relaxation leads to urination when appropriate.

Common Conditions

  • BPH (Benign Prostatic Hypertrophy): Enlarged prostate affecting urination in males.
  • UTI (Urinary Tract Infection): More common in females due to shorter urethra.

These notes should help as a study guide on the urinary system, focusing on the kidney's role in homeostasis and the anatomy and function of the urinary tract.

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