Human Anatomy and Physiology: Urinary System - Focus on the Kidney

Overview

• Primary Function: Process blood plasma to form urine.
• Functional Units: Nephrons (over a million in each kidney).

Kidney Structure

• Location: Protected by ribs and fat tissue.
• Main Structures:
  • Renal Arteries: Arise from abdominal aorta, deliver blood for filtration.
  • Renal Veins: Drain filtered blood into the inferior vena cava.
  • Calices (Minor and Major): Collect urine post-filtration.
  • Renal Pelvis: Funnel for urine collection leading to the ureter.
• Layers:
  • Renal Cortex: Outer layer.
  • Renal Medulla: Inner layer, contains calices and pelvis.

Nephron Anatomy

• Parts of a Nephron:
  • Renal Corpuscle:
    • Glomerulus: Tuft of capillaries for blood filtration.
    • Bowman’s Capsule: Surrounds glomerulus, filters small molecules from blood.
  • Renal Tubule:
    • Proximal Convoluted Tubule (PCT): High absorption and secretion.
    • Nephron Loop (Loop of Henle): Determines urine concentration.
    • Distal Convoluted Tubule (DCT): Further absorption and secretion.
    • Collecting Duct: Drains urine from several nephrons, responsive to ADH.

Urine Formation Process

• Filtration: Occurs at the renal corpuscle; based on particle size.
• Reabsorption and Secretion: Primarily in proximal tubule, lesser extent in distal tubule.
• Urine Concentration: Loop of Henle’s length influences concentration.

Hormonal Influence

• Anti-diuretic Hormone (ADH): Influences water reabsorption in collecting ducts.
  • Mechanism: ADH inserts aquaporin channels into cell membranes for water recovery.

Filtration Mechanism

• Filtration Slits:
  • Podocytes: Form filtration slits for selective permeability.
  • Fenestrations: Allow fluid/smaller solutes to pass, block larger molecules/cells.

This lecture covered the essential structures and functions of the kidney within the urinary system, emphasizing the roles of nephrons, filtration processes, and hormonal influences on urine formation.