Electrolytes absorption and secretion

Question 1

What is TF/P

Answer 1

[Tubular fluid]/[plasma]

Both creatinine and inulin go up steadily,
used as the border for reabsorption (below) and secretion

Question 2

How do you interpret TF/P?

Answer 2

TF/P >1 when solute is reabsorbed less quickly than water
(it is getting concentrated in the urine)

TF/p=1 when solute and water reabsorbed at the same rate

TF/p<1 whe solute is reabsorbed more quickly than water
(It is getting diluted in the urine)

Question 3

Things that are actively secreted in the urine

Answer 3

Above the inulin line:

PAH, Creatinine

Question 4

Things that are reabsorbed FASTER than water

Answer 4

Glucose, AA get absorbed the fastest,
Bicarb
Pi

Question 5

Things that are reabsorbed at the same rate as water

Answer 5

Na+
Osmolarity
K+ (slightly secreted, so above >1=TF/P)

Question 6

Things that are reabsorbed SLOWER than water

Answer 6

Cl- (then dips down slightly)

Urea

Question 7

Odd thing about Cl- absorption?

Answer 7

Cl- reabsorption occurs at a slower rate than Na+ in the proximal 1/3. of the proximal tubule;
Then matches the rate of Na+ reabsorption more distally.

Thus its relative concentration increases before it plateus.