Deck · USMLE Step 1
Renal & Urinary
Renal physiology and transport, fluid/electrolyte and acid-base disorders, AKI and CKD, glomerular and tubulointerstitial disease, stones, urinary tract pathology, and diuretics.
90 cards · audited · SM-2 spaced repetition
Included with the full USMLE Step 1 program — 14 decks, 1,546 cards.
Sample cards
What are the four functional segments of the nephron in order from glomerulus to collecting duct?
Proximal convoluted tubule → loop of Henle (thin descending, thin/thick ascending) → distal convoluted tubule → collecting duct.
Roughly what fraction of filtered Na+ and water is reabsorbed in the proximal convoluted tubule?
About 65-67% of filtered Na+ and water, reabsorbed isosmotically. The PCT reabsorbs the bulk of filtrate.
What substances are essentially completely reabsorbed in the early proximal tubule, and via what cotransporters?
Glucose and amino acids are nearly 100% reabsorbed via Na+-coupled cotransporters (SGLT for glucose). Bicarbonate is reclaimed via Na+/H+ exchange + carbonic anhydrase.
What is the transport mechanism of the thick ascending limb of the loop of Henle?
The Na+-K+-2Cl- (NKCC2) cotransporter on the apical membrane. It is impermeable to water, so it dilutes the filtrate while building the medullary interstitial gradient. K+ leaks back, creating a lumen-positive potential driving paracellular Ca2+/Mg2+ reabsorption.
Why is the thick ascending limb called the 'diluting segment'?
It actively reabsorbs NaCl but is impermeable to water, so the tubular fluid becomes hypotonic (dilute) while the medullary interstitium becomes hypertonic.
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