bulk reabsorption in the PCT Flashcards
sequence of events in the Nephron
filtration - pressure forces filtration of waste-laden blood in the glomerulus
reabsorption
secretion
what is reabsorption
process of returning important substances from filtrate back to body
what is secretion
movement of waste materials from the body to the filtrate
what is tubular reabsorption
process of returning important substances from filtrate back into renal interstitium then into renal blood vessels and then back to body
what do tubular cells have to increase surface area for reabsorption
microvilli/brush border on apical membrane
other components of tubular cells
large amount of NAK-ATPase on basolateral membrane
large amount of carbonic anhydrase enzyme
description of the oncotic pressure in the peritubular capillaries of the kidney
increased oncotic pressure compared with normal capillary blood
transportation of sodium in tubular reabsorption
actively transported over basolateral membrane (blood capillary side) of tubular cell out of tubular cells towards peritubular capillaries.
sets up sodium gradient which drives Na movement across apical (filtrate side) membrane
what follows sodium down its electrochemical gradient
negatively charged chloride
what follows sodium and chlorine when they set up an osmotic gradient
water by osmosis
what does the bulk movement of water cause
solvent drag
diffusion
what is glucose transport dependent on
specific membrane proteins
why is there not a limit on how much glucose can be filtered into the PCT?
glucose is freely filtered and does not saturate.
what does glucose filtration depend on
plasma concentration
why is glucose reabsorption from the PCT limited
rate of flow of the filtrate - decreased rate increases reabsorption
number of protein transporters
what substance does not exhibit a transport maximum but requires protein carriers
sodium
difference of phosphate reabsorption to glucose reabsorption
hormonally regulated
what hormone regulates phosphate reabsorption
parathyroid hormone
effect of PTH on phosphate reabsorption
reduces therefore increasing phosphate excretion
where does reabsorption occur
proximal convoluted tube (PCT)
what provides the energy for the transport from the lumen of the PCT back to the plasma
sodium/potassium pump
what does the sodium/potassium pump fuel
secondary active transport
diffusion
osmosis
functional adaptations of the PCT that enables large volume reabsorption of H20 and solutes
large surface area
single layer of epithelial cells
high concentration of Na, K ATPase
high concentration of carbonic anhydrase
asymmetrical distribution of Na, K ATPase
peritubular capillaries continuous with efferent arteriole have very high oncotic pressure
why is most of filtrate being immediately reabsorbed back into the blood in the PCT advantageous
able to swiftly remove toxic substances from the blood that are freely filtered at the renal corpuscle
