Renal Physiology: GFR and Blood Flow

Study Notes

Macula Densa and Glomerular Filtration Rate

Macula densa cells detect tubular fluid flow and composition.
These cells help regulate glomerular filtration rate (GFR).
They also influence renin secretion.
Lacis cells, similar to mesangial cells, are phagocytic.

Renal Blood Flow (RBF) and Renal Plasma Flow (RPF)

In resting adults, total kidney blood flow is approximately 1200 ml/min;
This represents approximately 22% of cardiac output.
The kidneys' combined weight accounts for less than 0.5% of total body weight.
Blood flow provides kidneys with nutrients and removes waste.
High renal blood flow substantially exceeds nutritional needs.
This surplus supports high glomerular filtration rates critical for precise fluid and solute balance.

Renal Blood Flow Regulation: Vasoconstrictors and Vasodilators

Adenosine:
- Produced in the kidneys.
- Causes afferent arteriole vasoconstriction, decreasing RBF and GFR.
- Involved in tubuloglomerular feedback.
Vasodilators:
- Nitric oxide:
  - Endothelial-derived factor.
  - Causes vasodilation of afferent and efferent arterioles.
  - Counteracts vasoconstriction from angiotensin II and catecholamines.
- Prostacyclin and prostaglandin E2 (prostaglandins):
  - May not be major regulators of RBF and GFR in health.
  - Important in pathological conditions like hemorrhage.
  - Produced locally to counteract vasoconstrictors (sympathetic nerves, angiotensin II).
  - Prevents severe vasoconstriction and renal ischemia.
- Bradykinin:
  - Produced in the kidney.
  - Vasodilator.
  - Increases GFR and RBF.
- Dopamine:
  - Produced in the kidney.
  - Renal vasodilator.

Description

This quiz covers key concepts in renal physiology, focusing on the macula densa, glomerular filtration rate (GFR), and the regulation of renal blood flow (RBF). Understand how these elements contribute to kidney function and homeostasis. Test your knowledge on the roles of different cells and substances in renal regulation.