Kidney Histology Lecture Notes

Introduction

• Function: Kidneys filter blood and produce urine.
• Structure: Consists of cortex, medulla, and renal sinus/calices.
• Nephron: Main functional unit, removes waste and excess water.

Kidney Structure

• Shape: Bean-shaped with convex lateral and concave medial surfaces.
• Components:
  • Cortex and Medulla: Cortex is the outer layer, medulla is inner, both have nephrons.
  • Renal Sinus: Contains calices, renal pelvis, and renal vessels.
  • Hilum: Passage for renal vessels and ureter.
• Protection: Enclosed by renal capsule and perinephric fat.
• Suprarenal Gland: Sits on the superior pole, separated by fat.

Cortex and Medulla

• Renal Cortex: Darker due to high blood supply, contains renal corpuscles and convoluted tubules.
• Renal Medulla: Appears striped, has renal pyramids and columns.
  • Pyramids: Project into minor calices via area cribrosa.
  • Lobes and Lobules: Each pyramid with cortex forms a lobe, lobes divided into lobules.

Nephron

• Types: Cortical (short tubules) and Juxtamedullary (long tubules).
• Components:
  • Renal Corpuscle: Includes glomerulus and Bowman's capsule.
  • Tubule System: Proximal tubule, nephron loop, distal tubule.
• Capillaries: Surround nephrons, secrete EPO.

Renal Corpuscle

• Structure: Glomerulus (capillary network) and Bowman's capsule.
• Filtration: Blood filtered to form ultrafiltrate.
• Layers:
  • Endothelium, glomerular basement membrane, podocytes.
• Function: Selectively filters water and solutes.

Renal Tubule System

• Parts:
  • Proximal Tubule: Convoluted and straight, reabsorbs water and molecules.
  • Nephron Loop: Descending (water permeable) and ascending (solute permeable) limbs.
  • Distal Tubule: Straight and convoluted, reabsorption, influenced by aldosterone.

Collecting System

• Function: Transfers urine from nephrons to minor calices.
• Structure: Cortical (cuboidal) and medullary (columnar) collecting ducts.
• Cells: Principal (ion transport) and intercalated (acid-base balance).

Juxtaglomerular Apparatus (JGA)

• Components: Macula densa, JG cells, and extraglomerular mesangial cells.
• Functions:
  • Regulates glomerular blood flow and filtration rate.
  • Regulates systemic blood pressure via renin-angiotensin-aldosterone system.

Secretion and Reabsorption

• Processes: Filtration, reabsorption, secretion, and excretion.
• Regulation: Hormonal and nervous system control.

Conclusion

• Urine Composition: Contains ions, urea, creatinine. Free from microorganisms, glucose, blood cells, and proteins.
• Study Aids: Videos, quizzes, and diagrams for better understanding.