Digestion/Absorption of Fluids and Electrolytes

Question 1

ion movement in intestines

Answer 1

small intestine

• absorb Na, Cl, K
• secrete HCO3

large intestine

• absorb Na Cl
• secrete K HCO3

Question 2

absorptagogues

Answer 2

somatostatin

NE

Question 3

mucosal resistance

Answer 3

dependent on paracellular resistance

increases as you move away from mouth and down crypt

Question 4

osmotic diarrhea

Answer 4

lactose intolerance is an example

Question 5

secretory diarrhea

Answer 5

induced by secretagogue

enterotoxins from bacteria

can be reversed with oral rehydration solution

Question 6

location of sodium absorption

Answer 6

villus of epithelium of small intestine

surface epithelium of large intestine

Question 7

Na/K pump

Answer 7

basolateral membrane

low intracellular Na results

Question 8

nutrient coupled Na transport

Answer 8

glucose or AA

uses Na gradient, and makes lumen negative

not inhibited by cAMP agonists**
bacteria enterotoxins

ex. SGLT1 or Na/AA co-transporters

Question 9

Na/H exhanger

Answer 9

aka NHE3 on apical surface

Na uptake with H extrusion
-decreases luminal pH

stimulated by bicarbo in duodenum

proximal small intestine - without Cl-HCO3 exchanger

Question 10

electroneutral NaCl absorption

Answer 10

Na-H coupled to Cl-HCO3

primary in between meals

ileum and large intestine

modulated by E. coli enterotoxin

• alters cAMP levels - inhibits absorption
• increased intracellular Ca

Question 11

electrogenic Na absorption

Answer 11

distal colon
against large gradients

enhanced by aldosterone (absorptagogue)
-important for Na conservation

depends on Na/K pump gradient

Question 12

passive Cl transport

Answer 12

voltage dependent
jejunum and distal colon

paracellular based on luminal charge

nutrient coupled Na absorption small intestine
electrogenic Na absorption in distal colon

-both create lumen negative potential

Question 13

active Cl transport

Answer 13

Cl-HCO3 exchanger on apical surface
-DRA exchanger

ileum

down regulated in cancer

Question 14

Cl-HCO3 exchanger

Answer 14

one Cl brought in / one HCO3 extruded

Question 15

congenital Cl diarrhea

Answer 15

absence of Cl-HCO3 exchanger

high Cl in stool and alkalotic plasma

Question 16

chloride secretion

Answer 16

promotes Na secretion secondarily (water follows)

basal state low

requires Na/K pump, Na/K/Cl cotransporter, and K channels

apical membrane has CFTR

Question 17

CFTR

Answer 17

cystic fibrosis transmembrane regulator
-Cl channel release from cell

cystic fibrosis - thick mucus

responsive to cAMP and Ca

Question 18

bacterial enterotoxins

Answer 18

increase cAMP - P of CFTR

• active Cl secretion and sodium and water follow
• diarrhea results

Question 19

K absorption

Answer 19

small intestine (passive)
 and distal colon (active)

Question 20

passive K absorption

Answer 20

solvent drag

• paracellular
• pulled through tight movements via water movement

small intestine

Question 21

active K absorption

Answer 21

distal colon
transcellular

apical H/K pump H into lumen
basolateral Na/K ATPase

Question 22

K secretion

Answer 22

large intestine only

passive K secretion
-driven by negative lumen

paracellular

Question 23

dehydration

Answer 23

aldosterone secretion

• lumen negative
• induces passive K secretion

Question 24

active K secretion

Answer 24

basally low

basolateral
-Na/K, Na/Cl/K cotransporter, K channel
apical
-K channel

activated by aldosterone and cAMP

Question 25

calcium absorption

Answer 25

active transcellular -only in duodenum villous epithelial cells -need Vit D

Question 26

VItamin D

Answer 26

induces synthesis of calbindin

Question 27

calbindin

Answer 27

binds calcium in cell (buffers in cell) chaperones to basolateral membrane -pumped through Na/Ca exchanger or Ca pump

Question 28

passive calcium absorption

Answer 28

paracellular not under control of Vit D through small intestine (J and I) enhanced by low plasma concentration

Question 29

Mg absorption

Answer 29

``` active transcellular (ileum) passive paracellular (Duodenum and J) ``` needed for PTH synthesis

Question 30

Mg deficiency

Answer 30

low PTH | -results in hypocalcemia

Question 31

ferric iron

Answer 31

Fe3

Question 32

ferrous iron

Answer 32

Fe2

Question 33

ascorbic acid

Answer 33

Vit C -complexes with iron and reduces to ferrous increased absorption

Question 34

anemia

Answer 34

iron depletion

Question 35

hemochromatosis

Answer 35

iron overload - increased in end organs - bronze pigmented skin women less susceptible bc of menstruation

Question 36

treatment of hemochromatosis

Answer 36

phlebotomize | -remove blood to reduce iron and ferritin levels

Question 37

heme iron

Answer 37

absorbed in duodenum | -endocytosis

Question 38

nonheme iron

Answer 38

absorbed less efficiently | -ferric preciptates

Question 39

DMT1

Answer 39

cotransport Fe2 (ferrous) and H into cell not specific for iron - divalent ions

Question 40

ferric reductase

Answer 40

Dcytb - reduces ferric iron to ferrous iron - on apical surface

Question 41

mobilferrin

Answer 41

Fe2 chaperone in cytoplasm to basolateral membrane

Question 42

ferroportin transporter

Answer 42

FP1 | -translocates Fe2 across basolateral membrane

Question 43

Fe in blood

Answer 43

Fe 3 binds to transferrin

Question 44

cholera enterotoxin

Answer 44

rice water stool | mucus in stool

Question 45

E coli enterotoxin

Answer 45

blood in stool

Question 46

diarrhea

Answer 46

Cl secretion activated by cAMP from enterotoxins

Question 47

cholera mechanism

Answer 47

increased cAMP secretion of Cl (CFTR) -Na and H2O follow Na absorption inhibition by cAMP get secretory diarrhea

Question 48

oral rehydration solution

Answer 48

glucose, sodium, Cl, bicarbonate use nutrient coupled movement of Na into cells reverse dehydration and metabolic acidosis