Kidney Structure and Function Lecture

Key Components of the Kidney

• Pyramids: Shaped like upside-down pyramids, with the apex facing downward.
• Main Sections
  • Cortex: Outer part, means "crust."
  • Medulla: Inner part, means "marrow."
  • Capsule: External to the cortex.
• Pyramids and Columns: Pyramids are found in the medulla, separated by renal columns.

Drainage System

• Minor Calyx: Drains each pyramid.
• Major Calyx: Formed by the fusion of minor calyces.
• Renal Pelvis: Drains into the ureter.
• Ureter: Leads to the urinary bladder.
• Urinary Bladder to Urethra: Final exit for urine.
• Hilum: Entry/exit point for ureter, blood vessels, lymphatics, nerves.
• Renal Sinus: Contains fat, blood vessels.

Functional and Structural Tissue

• Parenchyma: Functional tissue consisting of the cortex and pyramids.
• Stroma: Structural tissue, includes tubes like calyces.
• Nephron: Functional unit, located in pyramids.
• Renal Papilla: Nipple-like tip of the pyramid, drains into minor calyx.

Kidney Transplant Overview

• Donor kidney placed in pelvis of the recipient, typically without removing the failing kidney.
• Immunosuppressive drugs are necessary for life to prevent rejection.

Blood and Nerve Supply

• Sympathetic Stimulation: Kidney controlled by sympathetic nervous system, no parasympathetic supply.
• Blood Flow:
  • Renal Artery and Vein
  • Cardiac Output: 25% of resting cardiac output is directed to the kidneys.
  • Capillary Beds:
    • Glomerular Capillaries: Site of filtration.
    • Peritubular Capillaries: Surround nephron tubules for reabsorption.
    • Vasa Recta: Supplies nutrients to the medulla, maintains osmolarity.
• Renal Plexus: Sympathetic nerve supply, controls blood flow by altering arteriole diameter.

Nephrons

• Types
  • Cortical Nephron: Mostly in cortex, slightly dips into the medulla.
  • Juxtamedullary Nephron: Extensive loop in medulla.
• Blood Flow Pathway:
  • Renal artery -> series of arteries -> afferent arterioles -> glomerulus -> efferent arterioles -> peritubular capillaries -> venules -> renal vein.

Lecture Goals

1. List parts of the excretory system.
2. Describe macroscopic kidney structure and parts forming parenchyma and stroma.
3. Define parenchyma and stroma.
4. Identify components found in the renal sinus.
5. List retroperitoneal parts of the excretory system.
6. Define nephroptosis, afferent, and efferent.
7. Explain sympathetic control of kidney function.
8. Detail the three capillary systems in the kidney.
9. Describe a kidney transplant process.