Kidney Structure & Function Flashcards
What is the relation of the kidneys to the peritoneum?
Retroperitoneal
What percent of cardiac output goes to the kidneys?
20-25%
What constitutes the “maintenance” or homeostatic function of the kidneys?
- Maintain fluid balance
- Regulate quantity & concentration of extra-cellular fluid ions
- Maintain plasma volume & osmolarity
- Assist in acid-base balance
What constitutes the excretory functions of the kidneys?
- Excretion of end products of metabolism
2. Excretion of foreign compounds
What are the end products of metabolism and their origins?
- Urea (protein)
- Creatinine (muscle)
- Uric Acid (DNA & RNA)
- Bilirubin (haemoglobin) - excreted as urobilinogen
What metabolic functions do the kidneys have?
- Produce & secrete erythopoietin
- Secrete renin (vasoconstriction), kallikrein (vasodilation) and prostaglandins (paracrine activity)
- Convert vitamin D into it’s active form (1,25-dihydrocholecalciferol)
What are the main structural components of the nephron?
- Blood capillaries
- Glomerulus
- Afferent & Efferent arterioles
- Peritubular capillaries
- Bowman’s Capsule
- Proximal Convoluted Tubule
- Loop of Henle
- Distal Convoluted Tubule
- Collecting Duct
What is the histology of the PCT?
- Microvilli (apical brush border)
- Long & thin
- Mitochondria
NB: Site of most reabsorption - needs large surface area
What is the histology of the Loop of Henle?
- Thick & Thin portions
2. Ascending & Descending have different permeabilities
What is the histology of the DCT?
- Fewer microvilli compared to PCT
2. Low water permeability
What is the histology of the CD?
- Intercalated cells - Simple columnar, pale
2. Principle cells - Cuboidal, darker cytoplasm
What is the function of the PCT?
- Reabsortion:
- 65-70% of Na, Cl, K, water & solutes
- 100%~ of glucose & amino acids
- All processes are linked to ACTIVE Na reabsorption - Production & Secretion of EPO + Active vitamin D
- Secretion of H+
