proximal convoluting tubule physiology Flashcards
what is osmolality?
number of particles per Kg of solute (moles/Kg)
what is the osmolality in the proximal convoluted tubule?
300 mosm/L
what is tubular secretion?
substances moving from the blood into the kidney tubule (this is an active process)
what is tubular reabsorption?
-moving substances from the kidney tubule to the blood (Can be passive or active)
role of sodium potassium ATPase?
- pumps 2 K+ into the cell
- pumps 3Na+ out of the cell
role of sodium glucose transporters?
- Sodium is low in the cell (due to sodium potassium ATPase pumping out 3 sodium) so sodium can enter the cell with passive diffusion through the sodium glucose transporter
- there are high levels of glucose in the cell so it cannot diffuse into the cell
- however due to secondary active transport with the sodium glucose transporter, glucose can enter the cell through the sodium glucose transporter
what substances move into the cell with sodium through secondary active transport?
- glucose (SGLT)
- amino acids
- lactate
- H+ (sodium hydrogen antiporter, it moves out when sodium moves in)
- H2O (water follows salt)
- chloride
how does glucose enter the blood stream from the proximal convoluted tubule?
- sodium potassium ATPase causes 3 Na+ ions to leave the cell, decreasing concentration of Na+ in the cell
- Sodium then enters the cell through diffusion through the sodium glucose transporters, allowing glucose to also enter
- glucose then passes through glucose transporters at the cell basolateral membrane and into the blood stream (capillaries)
- lactate can also enter with glucose
how do amino acids enter the blood from the proximal convoluting tubule?
- sodium-potassium ATPase pumps out 3Na+ from the cells causing a decrease of sodium concentration in the cell
- sodium then moves from the proximal convoluted tubule and into the cell, allowing amino acids to also enter the cell, agaisnt their concentration gradient through secondary active transport
- amino acids then leave the cell and enter the blood stream through their transporter
in normal physiological conditions how much glucose, lactate and amino acids are reabsorbed from the kidney tubules and into the blood?
100% of it
what allows H+ to enter the proximal convoluting tubule from the cell?
-the sodium hydrogen antiporter
how do Calcium, magnesium and potassium leave the proximal convoluting tubule and enter the blood stream?
-through paracellular transport (moving between the cells) and into the blood stream
what type of substance is urea?
lipid
how do lipids pass out of the proximal convoluting tubule?
- lipid soluble substances can pass through the phospholipid bilayer
- urea (lipid) can just pass straight from the proximal convoluting tubule, through the cell and into the blood stream
how much glucose is reabsorbed in the proximal convoluting tubule?
100%