Renal Flashcards
Which part of the kidney is more prone to ischemic and toxic injury?
Medulla as it only received 3-10% of the overall blood flow to the kidneys.
Factors that determine the filtration of molecules at the glomerular capillaries:
- Size (< 4 nm) selectivity - lamina densa
- Charge selectivity - favour positively charged molecules - sialoglycoproteins and peptidoglycans at the capillary endothelium, lamina RI, lamina RE, podocytes all negatively charged
What are the 7 functions of the kidneys?
- Regulation of water and electrolyte balance
- Regulation of systemic blood pressure and extracellular fluid volume
a. Determine blood volume: salt and water balance
b. Production of vasoactive hormones: RAAS - Excretion of metabolic waste and foreign substances (uremic retention solutes)
- Regulation of red blood cell production: erythropoietin (synthesised by interstitial cells)
a- Stimulus: reduction in partial pressure of oxygen - Regulation of acid-base balance
- Regulation of Vit D production and calcium + phosphate balance
- Production of calcitriol (active Vit D) - Gluconeogenesis
What is the GFR of a dog?
3-5mL/kg/min
What is the GFR of a cat?
2.5-3.5mL/kg/min
What is the macula densa?
Specialised tubular epithelial cells that line the thick ascending loop of Henle at its junction with the distal tubules and sits in close contact with the afferent arterioles
What is the autoregulation range of the kidneys?
MAP 80-180mmHg
What is autoregulation
Intrinsic ability of kidneys to maintain RBF and GFR for varying BPs between 80-180mmHg
Name the 3 main ways Angiotensin II stimulates Na reabsorption:
- aldosterone secretion
- vasoconstriction of efferent arterioles
- direct stimulation of pumps in PT, LOH, DT and collecting tubules (Na-K ATPase, Na-bicarb cotransporter, Na/H+ antiporter luminal)
Where is aldosterone’s site of action?
principal cells of cortical collecting tubules
What does aldosterone do?
Na reabsorption (Na-K-ATPase basolateral, ENaC at luminal)
K+ secretion (ROMK in luminal)
Where does ADH act to increase water reabsorption?
V2 receptor in the late distal tubule and collecting ducts
How does ADH reabsorb water?
Synthesis + insertion of aquaporin 2 to luminal membrane
Where does ANP act?
- collecting ducts to inhibit Na and water reabsorption
- inhibits renin secretion
Which 2 mechanisms create the hyperosmotic medullary interstitium?
- loop of Henle’s countercurrent mechanism
- urea recycling