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?
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