Formation of Urine Flashcards
What are the 5 major stages of urine production
1) Glomerulus: filtration of blood
2) PCT: reabsorption of filtrate secretion into the tubule
3) LOH: concentration of urine
4) DCT: modification of urine
5) collecting duct: final modification of urine
Outline glomerular filtration
Blood enters via afferent arteriole and leaves via small efferent arterioles which creates a pressure in the glomerulus which drives the filtration. The blood has to pass through pores in the glomerular capillary endothelium, then the basement membrane of the Bowmans capsule and finally the podocytes via filtration slits.
What are forces involved in glomerular filtration
glomerular capillary hydrostatic pressure and Bowman’s space oncotic pressure is forcing contents through while the glomerular capillary oncotic pressure and Bowman’s space hydrostatic pressure is working the other way.
What is autoregulation of renal BP
GFR remains generally constant even when systemic BP changes.
What are the two hypotheses of autoregulation of renal blood flow
myogenic: due to a response of renal arterioles to stretch e.g. if bp decreases, renal artery and efferent arterioles automatically constrict to maintain RBF
metabolic: renal metabolites modulate afferent and efferent arteriolar contraction and dilation.
Outline the process of how the DCT affects systemic BP
A drop in GFR means fewer Na+ enters the PCT, the macula densa in the DCT senses a change in tubular Na+ levels and stimulates juxtaglomerular cells to release renin into the blood which leads to ang 2 production that causes vasoconstriction which causes BP to increase and as a result, GFR returns to normal.
Outline reabsorption into the peritubular capillaries
Na/k ATPase pumps out Na from the cells into the blood against chemical and electrical gradients. water follows the salt via AQP-1 and chloride ions also diffuse into the blood.
What are SGLT2 inhibitors
They make diabetic patients excrete more glucose in the urine to help reduce blood glucose levels by blocking na/glucose transporters.
