Proximal Convoluted Tubule – Flashcards
Unlock all answers in this set
Unlock answersquestion
proximal convoluted tubule
answer
most tubular reabsorption occurs here
question
sodium reabsorption
answer
creates an osmotic gradient and an electrical gradient to drive reabsorption of water and other solutes
question
sodium ions
answer
reabsorbed by symporters in first portion of PCT along with glucose, amino acids, phosphate ions
question
reabsorption continues..
answer
because of Na+/K+ pumps in the membrane
question
chloride ions
answer
gets reabsorbed because they follow sodium ions due to electrical attraction
question
water reabsorption
answer
raises chloride concentration in tubular fluid and creates a chloride gradient
question
bicarbonate ions
answer
seem to be reabsorbed from the filtrate, but they really aren't; illusion
question
bicarbonate ions are filtered out of the blood
answer
but urine is usually free of bicarbonate ions because they do not cross membrane of proximal convoluted tubule
question
bicarbonate ions combine with hydrogen ions
answer
that are present in tubular fluid to form carbonic acid, which dissociates into water and carbon dioxide
question
carbon dioxide
answer
enters tubules cells and combines with water to reform carbonic acid; dissociates into bicarbonate and hydrogen ions
question
bicarbonate ions..
answer
pumped into blood and hydrogen ions are pumped back into tubular fluid
question
one bicarbonate ion
answer
disappears from the tubular fluid as another appears in the blood
question
glucose
answer
co-transported with sodium ions by sodium-glucose transport proteins
question
glycosuria
answer
occurs when excess glucose remains in urine because glucose is not reabsorbed fast enough by symporters
question
nitrogenous wastes
answer
reabsorbed into the capillaries
question
urea
answer
40%-60% formed gets reabsorbed along with water
question
uric acid
answer
almost all gets reabsorbed, but some will be secreted back into tubular fluid later
question
creatinine
answer
isn't reabsorbed because it is too large
question
water
answer
gets reabsorbed into the peritubular capillaries by obligatory water reabsorption
question
about 2/3 of this water
answer
reabsorbed by aquaporins inn PCT
question
reabsorption of sodium ions and chloride ions
answer
and other solutes make tissue fluid hypertonic to tubular fluid
question
because the PCT reabsorbs proportionate amounts of water and solutes...
answer
osmolarity of tubular fluid remains relatively constant
question
Tubular secretion in the PCT
answer
extracts urea, uric acid, ammonia, other wastes from blood and transfers them into tubular fluid
question
secretion of uric acid
answer
compensates for its reabsorption and accounts for its presence in urine
question
aspirin, penicillin, and other drugs
answer
secreted into tubular fluid and cleared from blood
question
bicarbonate ions and hydrogen ions
answer
secreted into tubular fluid to regulate pH of body fluids
