reabsorption and secretion

Question 1

where is the major site of reabsorption taken place? what sort of things r reabsorbes there?

how do these reabsorbed material leave? via what?

Answer 1

PCT

– ~60-70% of Na and water

– ~80-90% of K+

– ~90% of HCO3-

– Normally, 100% of glucose and a.a

– Water follows osmotic gradients, so filtrate remains isotonic with plasma

– Reabsorbed materials leave by peritubular capillaries

Question 2

what r the 2 memebranes of the epithelial cells lining th tubules?

Answer 2

apical (lumnal) and basolateral side

Question 3

describe the free ion distribution across cell membranes

Answer 3

Question 5

what r the different types of transport?

Answer 5

Active transport: moves solutes from a region of their lower to a higher concentration (needs energy)

1. -Primary: transport coupled DIRECTLY to an energy source (ex: Na-K atpase pump, H+ atpase, Ca+ atpase)
2. -Secondary: (coupled transport or co-transport) 3aks primary, 2 or more substances interact w/ a specific membrane protein (Carrier) & r trasnported together across membrane

Osmosis: transport of water from areas of high to low concentration

Question 6

what sort of subctances r filtered in the kidney?

Answer 6

Question 7

what things r reabsorbed in the proximal tubule?

explain characterisitcs of proximal tubule

(early and late)

Answer 7

Early: Na+ & HCO_3- , (all nutrients, all glucose, aa, vitamins, urea, phosphate, Vb12, VD3, Ca+, Mg, other ions )

throughout: Cl-

Late: Na+ & Cl-

(cl shwaya reabsorbed mu wayd)

Question 10

how can particles transport across cell membranes?

Answer 10

transcellulary and paracellulary

Question 12

how is phosphate reabsorbed?

Answer 12

PTH blocks Na⁺/PO_4^3- cotranporter>>

therfore MORE phosphate excretion

Question 14

how is Vitamin B12 reabsorbed?

Answer 14

Transcobalamin (TC)

Vb12 needed for rbc formation, neurological formation, DNA synthesis

Question 15

how is a.a reabsorbed?

Answer 15

Question 16

how is Urea reabsrobed?

Answer 16

also via Na+

only about 1/2 of the Urea that is filteres is reabsorbed, u pee the remainder 1/2

Question 18

how is VD₃ reabsorbed?

Answer 18

Question 19

where is most water reabsorbed throughout the nephorn? via what mechanism?

Answer 19

Aquaporin 2 channels & via osmosis & ADH

(trancelullary and paracellulary)

ADH>> causes the insertion of aquaporins into the membranes of cells

Question 20

how is HCO3- reabsorbed?

Answer 20

1. in combination w/ Na+ (holds hands)
2. H+ r being secreted into tubulue and Na+ is reabsorbed>> NHE
3. HCO_3- is combined w/ H+>>bla bla>> the end product of CO₂ will be high, so it will rush into the tubular cells and be used again to form HCO_3-
4. HCO_3- that r formed again the tubular cells r reabsorbed via AE w/ Cl-

NHE, AE, Na-K ⁺ pump

Ann and edd do the HCO3- reabsobtion!

Question 21

how is Cl- reabsorbed?

Answer 21

1. Na-Cl co-transporter
2. Cl- dragged w/ water
3. Cl- diffused from high to low concentration (via tight junctions)
4. passively via paracellulary ( due Na leaving alot, leaving inside the cell negaitvely charged, charges repell!)

there is a high concentration of Cl- 2nd half of the PCT, bc when Na is reabsorbed, it carries glucose, HCO3- and ions w/ it in the early PCT, leaving behind a solution tha thas high Cl- in it. (favoring #3)

Question 22

Proportion of tubular ____ as the major anion increases as _____decreases

Answer 22

Proportion of tubular Cl- as the major anion increases as HCO_3^- decreases

Question 24

how is Glucose reabsorbed?

Answer 24

via SGLT2 in apical membrane

via GLUT 2 in basolateral membrane

Question 28

how is albumin reabsorbed?

Answer 28

.

Question 30

how is Ca²⁺ reabsorbed?

Answer 30

.

Question 31

the total solute concentration remians the same along the proximal tubule, why?

Answer 31

bc of the extrememly high permeability of this part of the nephron to water!

Question 32

what is the “solvent drag?”

Answer 32

as water moves across tight junctions by osmosis, it also pulls some of the solutes w/ it!

Question 33

NA is the BOSSSSS, if its reabsorption changes, it changes reabsorption of water and many other solutes!!!

Answer 33

cool

Question 34

secretion in Proximal tubule

Answer 34

Organic acids: penicillin, thiazide diuretics, p-aminohippurate (PAH), uric acid?

Strong organic bases: histamine, choline, thiamine, guanine, creatinine? tetraethylammonium?

EDTA (ethylenediaminetetraceticacid)

PAH

(para-aminohippuric acid)

Question 35

why is the total solute concentration remian essentialy the same along the proximal tubule?

Answer 35

bc of the extreemely high permeability of this part of the nephron to water,

water reapsorbtion keeps in pace w/ the Na+ reabsorption

Question 36

reabsorbed materials leave via the ________

Answer 36

peritubular capillaries