Renal Physiology 2 (Renal) Flashcards
Where does pinocytosis occur in the nephron?
Proximal convoluted tubule.
Describe tubular reabsorption amounts for different compounds: water, glucose, sodium, chloride, potassium, urea and creatinine.
Almost all of water, glucose, sodium and chloride is reabsorbed.
Most of the potassium is reabsorbed, but some is lost due to leakage in exchange for sodium reabsorption.
50% of urea is reabsorbed.
NO creatinine is reabsorbed.
What is the difference in saturation of active and passive transport giving examples.
Active transport is saturable e.g. glucose
Passive transport is not saturable, dependent only on electrochemical gradient, permeability.
Describe the ‘leakiness’ of different parts of the nephron to water.
PCT is very leaky. Water follows Na+ quickly.
Ascending LoH is impermeable. No aquaporins with very tight TJs.
DCT/CD have varialbe permeability depend on what we need.
Where does reabsorption of ALL glucose, amino acids and small proteins back into blood occur?
Proximal convoluted tubule.
Co transport of sodium-glucose, sodium-AA
Describe reabsorption of water in the nephron.
65% reabsorption in PCT - Obligatory
15% reabsorption in descending LoH - Obligatory
20% reabsorption in DCT and CD is varaible, based on hormonal control.
Obligatory = follows sodium, not regulated.
Hormonal control of DCT/CD allows for different %’s of Na+ and water to be reabsorbed.
Describe the reabsorption of Na in the nephron.
67% in PCT - Obligatory
25% in LoH - Obligatory
8% in DCT - Hormonal control
Where are most wastes and H+ secreted into tubular fluid? Give examples of waste products.
Most secreted in PCT
NH3, bile salts, urate, creatinine.
What feature of the PCT allows for maximal exchange to take place?
Extensive brush border - huge SA, loaded with carriers (Na+/K+ ATPase, aquaporins)
Differentiate between descending and ascending loops of Henle.
Descending LoH is highly permeable to water. Thin. Few mitochondria as there is minimal metabolic activity.
Ascending LoH is thick, impermeable to water. Undergoes active reabsorption of Na+, Cl-, K+
Differentiate between early and late DCT
Early DCT is the same as teh thick, ascending LoH - IMPERMEABLE salt resorber.
Late DCT has two cells types:
Principal cells - reabsorb Na and secrete K
Intercalated cells - secrete H+, reabsorb HCO3- and K+
How do we create concentrated urine?
In juxtamedullary nephrons.
We need to open aquaporins.
Need leaky DCT/CT/CD
Need hyperosmotic renal medullary interstitum (created through urea recirculation)
What is the obligatory urine volume, based on maximum urine concentration?
Humans must excrete ~600mOsmoles of solute a day.
maximum urine concentration posssible is 1200mOsm/L, so minimum urine output is 0.5L.
