Lecture 4 Reabsorption and Secretion Flashcards
What percentage of plasma is filtered into the bowman’s capsule from the glomerulus
20%
What happens when carriers maximum transport capacity in exceeded
Excess substrate enters the kidneys
Up to how many mmoles/l will the be absorbed in man before it appears in the urine
10mmoles/l
if plasma glucose os 15mmoles/l how much will be absorbed and how much will be excreted
10 mmoles/l absorbed
5 moles/l secreted
What levels of sulphate and phosphate lead to saturation and excretion
Normal levels
What is the most abundant ion in the ECF
Na+
Where does majority of Na+ ion resorption occur
Proximal tubule
How is Na+ reabsorbed
• Not reabsorbed by a Tm mechanism, but by active transport, which establishes a gradient for Na+ across the tubule wall.
Moves Na+ into blood and K+ into cell to create a gradient for Na+ to passively move into the tubule cells across the luminal surface
Why does the proximal tubule cells brush border have a high permeability to Na+ ions
Enormous surface area offered by the microvilli and larger number of Na+ ion channels
The active transport of Na+ leads to the movement of what other components
Cl- (passie) and H2O (osmosis)
Permeable solutes are reabsorbed by diffusion as the fluid volume in the lumen has decreased
What percentage of urea is absorbed
50%
Remainder stays in tubule
The tubular membrane is impermeable to
Inulin and mannitol
What substances share the same carrier molecule as Na+ (symport)
Glucose
Amino acids
Tubular secretion in the peritubular lumen is important for ___
Elimination of potentially harmful substances
The amount of solute secreted can be calculated by
Amount filtered - amount reabsorbed + amount secreted
