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Flashcards in renal function 4b Deck (18):

180L of fluid passes through the glomerular capillaries but only 1.5L is excreted as urine out of the body



what percent is reabsorbed back into the blood

99% of the fluid is reabsorbed back into the blood as it passed through the nephron


where in the nephron does reabsorption occur

mostly in the proximal tubule but very little in the distal segment of the nephron
regulated reabsorption in the distal nephron is important in selectively returning water and ions into the blood


how is water and ion reabosrbed from the tubule to the ECF?

active transport


how is Na reabsorbed from the lumen to the ECF

Na uses active transport


how are anions reabsorbed from lumen to the ECF

when the Na leaves the lumen, it creates a transepithelial electrochemical gradient. the lumen is negative so, the anions flow towards the positive ECF


how does water get reabsorbed from the lumen to the ECF

when the anions and Na leave the lumen, the lumen becomes diluted while the ECF is highly concentrated, so water return to the ECF through osmosis


how do solutes (K and Ca) leave the lumen

when the concentration of the solutes are higher in the lumen than ECF, the solutes diffuse through the epithelium, if it is permeable into the ECF


what type of transports does reabsorption involve?

- epithelial transport, substance move through the apical and basolateral membrane of the tubule epithelial cells
- paracellular transport, substances go through cell-cell junction b/w two adjacent cells


are protiens found in the urine ?

yes really small protiens , < 50 Kda, glycoprotien hormones, and other protein hormones


how are the proteins reabsorbed into the capillary?

proteins are too big to be reabsorbed, they enter the proximal tubule cells via receptor-mediated endocytosis, where the proteins are digested by lysosomes into smaller AA that can cross the epithelium into the blood


what is renal threshold

the plasma concentration at which glucose appears in the urine


How does that reabsorbed fluid then get into the capillary?

- the hydrostatic pressure ( pressure that results solute and ions to move from capillary to tubule) is less than colloid osmotic pressure so, it favours reabsorption


Secretion like reabsorption depends mostly on membrane transport system



what is secreted in the distal nephron and why

K+ and H+ are secreted in distal nephron bc it is important in homeostatic regulation of these ions


what type of transport is secretion

secretion is active transport, as most substrates must move against the concentration gradient


what is OAT

organic anion transporters that transport a wide range of anions endogeneous and exogeneous anions
secretion of organic anions is a tertiary active transport


what are the steps of secreting an organic anion in the proximal tubule

1. direct transport: proximal tubules use ATP to maintain low concentration of intercellular NA
2. the Na gradient is then used to concentrate dicarboxylate in the tubule cells using Na- dicarboxylate cotransporters known as NaDc found o the apical and basolateral membrane of the proximal tubule
3. OAT in an indirect active transporter that used the Na-dicarboxylate going down its concentration gradient, to move an organic anion against its concentration into the tubule cell
4. when the tubule cell us concentrated with organic anion, it will use facilitated diffusion to diffuse into the lumen