Renal Physiology Part 6 Flashcards
(17 cards)
What are the two main pathways of tubular reabsorption?
Paracellular transport and transcellular pathway.
What characterizes paracellular transport?
It involves passive diffusion only, passes through tight junctions, and accounts for 5–10% of water reabsorption, along with some ions and large non-polar solutes.
What characterizes the transcellular pathway?
It includes all active transport and passive diffusion, responsible for 90–95% of water reabsorption.
How is sodium transported out of tubular cells into the blood?
Actively transported via the Sodium-Potassium Pump (Na⁺/K⁺-ATPase) at the basolateral membrane.
How does sodium move into tubular cells from the lumen?
Sodium moves passively via facilitated diffusion across the luminal membrane.
What role does the Sodium-Potassium Pump play in reabsorption?
It maintains a sodium gradient by pumping sodium out and potassium in, which drives passive sodium entry from the lumen.
What is a secondary active cotransporter?
A transporter that allows two or more substances to interact with a specific carrier in the cell membrane and be translocated across it, often using the sodium gradient.
What is the transport maximum (Tm)?
It refers to the limit of how much material can be transported across the membrane, beyond which excess substances appear in urine.
What are common substances reabsorbed using secondary active cotransporters?
Glucose and amino acids.
Where does the majority of sodium and water reabsorption occur in the nephron?
In the proximal tubule (about two-thirds of total reabsorption).
Which parts of the nephron are primarily under hormonal control for reabsorption?
The distal convoluted tubules and collecting ducts.
Is sodium (Na⁺) reabsorption passive or active?
Na⁺ reabsorption is an active process that occurs in all tubular segments except the descending limb of the loop of Henle.
How is water reabsorbed in the nephron?
Water reabsorption occurs by osmosis and is dependent on Na⁺ reabsorption.
What percentage of filtered Na⁺ is reabsorbed in the proximal tubule?
About 65–70% of filtered sodium is reabsorbed in the proximal tubule.
How is water reabsorbed in the nephron?
Water reabsorption occurs by osmosis and is dependent on Na⁺ reabsorption.
What co-transport mechanisms are involved in Na⁺ reabsorption in the proximal tubule?
• Na⁺–Glucose co-transport
• Na⁺–Amino acids co-transport
What is the main counter-transport mechanism for Na⁺ in the proximal tubule?
Na⁺–H⁺ exchange (counter-transport).
