Lecture 25 Flashcards Preview

Anatomy and Physiology II > Lecture 25 > Flashcards

Flashcards in Lecture 25 Deck (33):
1

Reabsorption of Bicarbonate, Na+ & H+ Ions: What reabsorbs Na+ and secretes H+?

1. Na+ antiporters
-PCT cells produce the H+ & release bicarbonate ion to the peritubular capillaries
-important buffering system

2

***For every H+ secreted into the tubular fluid,

one filtered bicarbonate eventually returns to the blood

3

secretion =

blood to tubule

4

reabsorption =

tubule to blood

5

Passive Reabsorption in the 2nd Half of PCT: Electrochemical gradients produced by

symporters & antiporters causes passive reabsorption of other solutes

6

What passively diffuses into peritubular capillaries?

Cl-, K+, Ca+2, Mg+2 and urea

7

What promotes osmosis in PCT?

Passive Reabsorption in the 2nd Half of PCT-
VERY permeable because of aquaporin-1 channels

8

Ammonia (NH3) is a

-poisonous waste product of protein deamination in the liver
-most is converted to urea which is less toxic

9

Both ammonia & urea are

filtered at the glomerus & secreted in the PCT

10

PCT cells do what?

deaminate glutamine in a process that generates both NH3 and new bicarbonate ion.

11

Bicarbonate diffuses into what?

-the bloodstream
-

12

during acidosis more what is generated?

bicarbonate

13

Reabsorption in the Loop of Henle:

-Tubular fluid
-Sets the stage for independent regulation of both volume & osmolarity of body fluids

14

Tubular fluid has PCT that does what?

-reabsorb 65% of the filtered water so chemical composition of tubular fluid in the loop of Henle is quite different from plasma

15

Osmolarity of tubular fluid is close to that of blood because why?

Since many nutrients were reabsorbed as well

16

Symporters in the Loop of Henle: Thick limb of loop of Henle has

Na+ K- Cl- symporters that reabsorb these ions

17

Symporters in the Loop of Henle: K+ leaks through

K+ channels back into the tubular fluid leaving the interstitial fluid and blood with a negative charge

18

Symporters in the Loop of Henle: Cations do what?

passively move to the vasa recta

19

Reabsorption in the DCT: 1. Removal of Na+ and Cl- continues in

the DCT by means of Na+ Cl- symporters

20

Reabsorption in the DCT: 2. Na+ and Cl- then reabsorbed into

peritubular capillaries

21

***DCT is major site

where parathyroid hormone stimulates reabsorption of Ca+2

22

***DCT is not very permeable to

water so it is not reabsorbed with little accompanying water

23

Reabsorption & Secretion in the Collecting Duct: By end of DCT,

95% of solutes & water have been reabsorbed and returned to the bloodstream

24

***Reabsorption & Secretion in the Collecting Duct: 2 Cell types in the collecting duct make the final adjustments

1. Principal cells
2. Intercalated cells

25

***Principal cells do what?

reabsorb Na+ and secrete K+

26

***Intercalated cells do what?

reabsorb K+ & bicarbonate ions and secrete H+ (buffering, ex. pH)

27

Actions of the Principal Cells: 1st step

Na+ enters principal cellsthrough leakage channels

28

Actions of the Principal Cells: 2nd step

Na+ pumps keep theconcentration of Na+ inthe cytosol low

29

Actions of the Principal Cells: 3rd step

Cells secrete variableamounts of K+, to adjustfor dietary changes in K+intake
-down concentration gradient due to Na+/K+ pump

30

Actions of the Principal Cells: 4th step

Aldosterone (hormone) increases Na+ and water reabsorption & K+ secretion by principal cells by stimulating the synthesis of new pumps and channels

31

Secretion of H+ and Absorption of Bicarbonate by Intercalated Cells: 1st Step =

Proton pumps secrete H+ into tubular fluid
-can secrete against a concentration gradient so urine can be 1000 times more acidic than blood

32

Secretion of H+ and Absorption of Bicarbonate by Intercalated Cells: 2nd Step =

Cl-/HCO3- antiporters move bicarbonate ions into the blood
-intercalated cells help regulate pH of body fluids

33

Secretion of H+ and Absorption of Bicarbonate by Intercalated Cells: 3rd Step =

Urine is buffered by HPO4 2- and ammonia, both of which combine irreversibly with H+ and are excreted
-get rid of waste w/o destroying body