Detailed Notes on Kidney Structure and Nephron Function

Structure of the Kidney

• Kidney Overview

  • Kidneys are crucial for maintaining homeostasis, particularly in regulating water and electrolytes.
  • Two main regions: cortex and medulla.

• Cortex

  • Contains:
  • Bowman's capsules
  • Convoluted tubules (proximal and distal)
  • Functions primarily in filtration and reabsorption.

• Medulla

  • Contains loops of Henle and collecting ducts.
  • Collecting ducts drain urine into the renal pelvis.

Nephron Structure and Function

• Nephron Overview
  • The basic structural and functional unit of kidneys.
  • Each nephron consists of:
  • Bowman's capsule: A cup-shaped structure at the start of the nephron.
  • Glomerulus: A knot of blood capillaries inside the Bowman's capsule.
  • Tubule: Part of the nephron where urine is formed.
    • Proximal convoluted tubule: First section of the tubule, involved in reabsorption.
    • Loop of Henle: Located in the medulla, plays a critical role in concentrating urine.
    • Distal convoluted tubule: Final segment before urine enters the collecting ducts.

Main Functions of Nephrons

• Ultrafiltration

  • The process where blood pressure forces water and solutes from the glomerulus into the Bowman's capsule.
  • Results in the formation of a filtrate, which contains waste products and essential substances.

• Selective Reabsorption

  • The process of reabsorbing essential substances (like glucose, salts, and water) from the filtrate back into the bloodstream.
  • Occurs primarily in the proximal convoluted tubule and parts of the Loop of Henle.

Collecting Ducts

• Collect urine from multiple nephrons and direct it into the renal pelvis, where it will then flow into the ureter for excretion.
  • The collecting ducts also play a role in water reabsorption, influenced by hormones (e.g., ADH).