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Gastro > Digestion and Abs 2 (Johnson) > Flashcards

Digestion and Abs 2 (Johnson) Flashcards

1
Q

Sources of fluids entering small intestine?

A 
diet
saliva
gastric secretion
bile
pancreatic secretion
sm intestinal secretion
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2
Q

Fluids are absorbed by:

A

dueodenum/jejunum (4L)
ileum (3.5L)
colon (1.4L)

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3
Q

What is NOT present in feces?

A

almost all nutrients, electrolytes, and all but 100-200mL fluid)

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4
Q

By what mechanism are water and electrolytes absorbed?

A

transcellularly

paracellularly (via tight junctions)

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5
Q

Duodenum tight junctions are very (loose/tight)

A

loose–water easily absorbed

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6
Q

Tightest tight junctions are found in the:

A

colon

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7
Q

What are the fat-soluble vitamins?

A

ADEK

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8
Q

What frees up B12 during absorption?

A

pepsin

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9
Q

Binds B12 in stomach (protective)

A

heptacorn

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10
Q

What happens to B12 once it passes in to duodenum?

A

heptacorn degraded, intrinsic factor complexes with B12

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11
Q

What is the function of intrinsic factor?

A

binds B12 in duodenum, protects it in passage from small bowel to ileum

in ileum, intrinsic factor is recognized by its carrier and allows for uptake of B12

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12
Q

All mechanisms for Na+ absorption depend on:

A

gradient established by Na/K/ATPase located at basolateral membrane

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13
Q

How is Na+ taken up from the mucosal solution at apical membrane? (4 mechanisms)

A
  1. Na+ channel, most likely located in colon
  2. Na+ w/ sugar or amino acid
  3. Na+/Cl- cotransport (elec neutral)
  4. Na+/H+ exchange (elec neutral)
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14
Q

In the COLON,

HCO3- is exchanged for ____, which is then:

A

Cl-

reabsorbed into serosal solution w/ H+

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15
Q

Why is stool H2O alkalinic?

A

the colon exchanges Cl- for bicarb, so high levels of bicarb in feces

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16
Q

What mechanism of electrolyte absorption predominates in the small intestine?

A

paracellular

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17
Q

The amount of K excreted depends on:

How + why?

A

aldosterone: activates Na channels and increases # of Na/K/ATPases in basolateral membrane

goal = conserve Na

18
Q

In the COLON,

K+ is exchanged for ____

A

Na+

K excreted, Na absorbed

19
Q

How is water absorption different in the prox small bowel versus the colon?

A

colon = tight junctions, not much water abs

PSB = “leaky” and water follows Na via osmosis

20
Q

By the time that small amount of water is excreted, it is (hypo/hyper/iso)-tonic

A

iso

due to bacteria

21
Q

The small intestine secretes ___ liter of H2O per day via (what structural component?).

A

1

crypts

(probably to keep chyme liquidy)

22
Q

How does secretion of water from crypt cells occur (in terms of ions and water)?

A

On apical/serosal side:

  • -Na is actively pumped out of cell, K diffuses out via channel
  • -Na+/K+ brought back in along with 2 Cl-

On basolateral/mucosal side:

  • -Cl- leaves cell via channels (2 types)
  • -Na+ diffuses paracellularly

NaCl secreted, and H2O follows!

23
Q

What types of Ca channels are located in crypt cells on apical membrane?

A

cAMP-activated

Ca-activated

24
Q

What causes watery diarrhea in bacterial infections?

A 
bacterial toxins (like in cholera) stimulate adenylate cyclase; cAMP then activates Cl- channel 
(this drives NaCl and H2O secretion)
25
Q

What condition is seen in Cl- channel abn on the basolateral membrane?

A

cystic fibrosis

26
Q

What is osmotic diarrhea?

What can cause this?

A

impaired absorption –> accumulation of solutes

lack of enzymes
decr absorptive surface
ppt of bile salts
hypermotility

27
Q

What is secretory diarrhea?

What can cause this?

A

increased secretion from crypt cells

bacteria (cholera)
increased secretory hormones (VIP)
incr adenylate cyclase
activation of apical Cl- channels

28
Q

Ca++ absorption from gut depends on:

A

PTH + VitD3

29
Q

1,25-OH2-D3 acts on nucleus to produce:

A

Ca binding protein

Ca-ATPase

30
Q

Fe absorption is regulated by:

A

levels of ferritin and transferrin

31
Q

He just said this class is not overweight…“for the most part”

A

Awkward…

32
Q

Integrates signals from endo, GIT and CNS to drive satiety

A

arcuate nucleus

has POMC, NPY/AgRP

33
Q

POMC –> ______ (hormone) –> activation of ____ receptor

A

alpha-melanocyte stimulating hormone

MC4

34
Q

decr food intake (=satiety), incr metabolism

A

alpha-MSH

M=metabolism

35
Q

incr food intake, decr metabolism

A

NPY

36
Q

What is the function of AgRP?

A

promotes action of NPY by blocking MC4R

blocks satiety/incr metabolism

37
Q

What induces NPY production?

A

hunger

38
Q

What inh NPY production?

A

incr metabolism

satiety

39
Q

Stimulated by vagal nerve; Inh food intake and acts on hypothalamus/AN

A

NTS

don’t really know what this is?

40
Q

Hormones which decr appetite:

A

CCK
insulin
leptin
PYY

41
Q

Hormone which incr appetite:

A

ghrelin

42
Q

Hormones which inh NPY and activate POMC:

A

leptin

PYY

Gastro (25 decks)

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