Kidney Structure Flashcards
Nephron
Functional unit of the kidney, wall are 1 cell thick
How many nephrons are there per kidney?
I million
Glomerulus
Capillary bed inside Bowman’s Capsule
Vasa Recta
Capillary network surrounding each nephron, important for reabsorption and secretion
Diluting
Above 300mOsm
Dehydrating
Below 300mOsm
Osmolarity of blood
300mOsm
What determines how concentrated urine can be?
Loop of Henle length and size of osmotic gradient
PCT
Proximal Convoluted Tubule, 2/3s of initial filtrate reabsorbed
Descending Loop of Henle
Water reabsorption continues, osmolarity of pre-urine at bottom is 1200
Ascending Loop of Henle
Salt reabsorption occurs here, not permeable to water
Diluting Segment
Thick part of the ascending loop of henle, osmolarity at the end of the DS is 100mOsm
Distal Convoluted Tubule and Cortical Collecting Duct
Action depends on hormones and acid-base balance, aldosterone stimulates Na+ reabsorption and K+ secretion, H+ can be secreted into pre-urine, permeable to H2O only when ADH is high
ADH
Causes insertion of H2O channels through membrane, aquaporines, allows pre-urine to equilibrate with hi extracellular osmolarity of medulla
Medullary Collecting Ducts
H2O reabsorption, permeable to H2O only when ADH is high, very permeable to urea
Urea
A toxic nitrogenous waste product of protein metabolism, becomes concentrated approx 65x in the nephron, diffuses down its concentration gradient into the extracellular fluid and is passively transported
Low ADH
Urine is approx 100mOsm
High ADH
Urine is approx 1200mOsm
Ethanol (ETDH)
Dehydrates by inhibiting ADH so there is no insertion of aquaporines
3 Steps of Urine Formation
Filtration, reabsorption, and secretion
Filtration
Driven by blood pressure in glomerulus, non-selective, 15-25% of water and solutes passing through glomerulus are filtered
Reabsorption
99% of filtered H2O and salts are reabsorbed before kidney produces final urine, approx 100% of important cmpds like glucose, vitamins, and AAs are reabsorbed
