B5.020 Prework 1 Water and Electrolyte Absorption and Secretion Flashcards Preview

GIR Test 1 > B5.020 Prework 1 Water and Electrolyte Absorption and Secretion > Flashcards

Flashcards in B5.020 Prework 1 Water and Electrolyte Absorption and Secretion Deck (24)
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1
Q

when does diarrhea manifest

A

both the small intestine and colon have a large reserve capacity for reabsorption, diarrhea manifests when this is exceeded

2
Q

intracellular tight junctions

A

restrict passive flow across the intestinal epithelium in response to established osmotic gradients

3
Q

function of transcellular proteins

A

workhorse of intestinal luminal activity
move molecules and water through cells
may work against electrochemical gradients (require energy)
subject to transcriptional and post-transcriptional regulation

4
Q

active transport

A

requires ATP for movement of molecules across the membrane

5
Q

primary active transport

A

the ATP driven Na+/K+ stores energy by creating a steep concentration gradient for Na+ entry into the cell

6
Q

secondary active transport

A

as Na+ diffuses back across the membrane through a membrane cotransporter protein, it drives glucose against its concentration gradient into the cell

7
Q

paracellular trans-epithelial transport

A

movement of solutes and water through tight junctions

dictated primarily by electrochemical gradient

8
Q

3 key points surrounding the process of trans epithelial transport

A
  1. membrane transport proteins drive transcellular transport of ions
  2. transport of ions sets up electrochemical gradients
  3. electrochemical gradients allow paracellular transport of fluid through tight junctions
9
Q

differences between small intestine and colon absorption functions

A

small intestine: tight junctions more permeable, larger passive flux of fluids, absorption of nutrients, vitamins, minerals, salt and water
colon: tight junctions less permeable, only absorption of sodium and water favored

10
Q

effect of motility on absorption/secretion

A

motility/transit time increased: less time for absorption across epithelium
motility/transit time decreased: more time for absorption across epithelium

11
Q

function of villi

A

absorption
fluid absorption primarily depends on Na+ transport
Na+ may be coupled with Cl-, nutrients, bile acids, and other solutes

12
Q

function of crypts

A

secretion

primarily follows Cl- and bicarb

13
Q

small intestine ion transport mechanisms

A

bicarb secretion
electroneutral NaCl absorption
chloride secretion

14
Q

small intestine nutrient/mineral/other transport mechanisms

A
Na+ coupled nutrient absorption
H+ coupled nutrient absorption
N+ coupled bile acid absorption
Ca2+ absorption
Fe absorption
15
Q

colon ion transport mechanisms

A

Na+ absorption
K+ secretion and absorption
Cl- secretion
short chain fatty acid absorption

16
Q

mediators that regulate transport mechanisms in diarrhea

A
infection
inflammation
gut hormones
chemical mediators
enteric nervous system
17
Q

action of Na+/K+ ATPase

A

on basolateral side of enterocytes
actively drives sodium out of cell and potassium in at a ratio of 3:2
creates a Na+ electrochemical gradient between enterocyte and lumen

18
Q

glucose/AA transport

A

fostered by the electrochemical gradient established by Na+/K+ ATPase
proteins along apical aspect of enterocyte utilize Na+ transport to facilitate absorption of glucose and AAs

19
Q

SGLT1 transporter in context of diarrhea

A

preserved function
allows oral rehydration using glucose coupled sodium absorption to promote fluid absorption by coupling sodium with glucose in solution

20
Q

NaCl transport

A

NaCl is absorbed in conjunction with export of H+ and bicarb
relies on Na+/K+ ATPase to establish gradient
Na+/H+ cation exchanger works in conjunction with Cl-/HCO3- exchanger allowing NaCl reabsorption

21
Q

KCC1

A

co transport of Cl- and K+

22
Q

CFTR function

A

coupled import of Na, K, and Cl in basolateral membrane
as intracellular Cl increases, Cl is secreted via apical CFTR
CFTR expression highest in ileum and colon
relevant to secretory diarrhea

23
Q

osmotic diarrhea

A

solute driven water losses, more prominent in colon
non absorbed solutes create intraluminal concentration gradients that draw in fluid into the lumen and promote fluid loss
carb malabsorption common example

24
Q

secretory diarrhea

A

crypt secretion leads to more prominent small intestine losses
due to dysregulation of intestinal ion transport which leads to imbalance of ion secretion/absorption
favors secretion, water follows