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Physiology Exam 3 > GI 2 > Flashcards

GI 2 Flashcards

1
Q

where is digestion initiated

A

in the mouth

  • chewing
  • saliva
  • swallow
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2
Q

when is bolus referred to as chyme

A

once enters the stomach

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3
Q

explain the anatomy breakdown of intestine

A

first 1/3: duodenum
middle 1/3: jejunum
final 1/3: ileum

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4
Q

trace pathway of food bolus from mouth to small intestine

A

mouth–>esophagus–>stomach–>SI

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5
Q

how much fluid is absorbed compared to how much is excreted from the body and where is it mostly absorbed

A

massive amount of fluid is absorbed in the SI

much more than is excreted from the body (minimal amount is excreted in urine and feces)

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6
Q

layers of GI tissues from lumen to just lining abdominal cavity

A
  1. mucosa
    - single layer of epithelial cells
    - lamina propria
    - muscularis mucosa
  2. submucosa
    - major blood vessels
    - submucosal nerve plexus
  3. muscularis externa
    - circular muscle
    - myenteric nerve plexus
    - longitudinal muscle
  4. serosa
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7
Q

what two cells are found in the lamina propria of GI tissue

A

stromal cells and fibroblasts

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8
Q

how is surface area increased in small intestine

A

finger like projections

microvilli “brush border”

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9
Q

what is present within each microvillus?

A

capillary bed

lacteal

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10
Q

what is a lacteal

A

lymphatic duct responsible for absorbing fats

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11
Q

5 basic categories of useable food

A 
carbs
proteins
fat
vitamins
minerals
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12
Q

when we eat carbs what form do we usually get from our diet

A

polysaccharides
disaccharides
DO NOT get monosaccharides

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13
Q

what form does carb have to be in to be absorbed into the blood

A

monosaccharide

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14
Q

polysaccharides

A

starch
glycogen
cellulose

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15
Q

disaccharides

A

sucrose
lactose
maltose

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16
Q

monosaccharides

A

glucose
fructose
galactose

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17
Q

where are ectoenzymes and what do they do

A

ectoenzymes are bound to the membrane of the brush border in the intestine

break down disaccharides to monosaccharides

ex: lactase

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18
Q

how are monosaccharides absorbed through the intestinal tissue

A
  1. Na/K pump creates Na gradient
    - Na high outside cell, low inside cell, will want to move into cell
  2. Na and glucose symporter pumps into cell (SGLT1)
  3. Fructose will follow concentration gradient and diffuse into cell (GLUT5)
  4. GLUT2 transporter will move glucose, fructose, galactose into blood
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19
Q

what effect do sweetners have in the absorption in the SI

A

increase expression of GLUT2 transporter

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20
Q

proteins are broken down into

A

amino acids

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21
Q

where are 2 locations proteins are broken down

A

stomach

small intestine

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22
Q

what proenzyme is produced in the stomach

A

pepsinogen

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23
Q

pepsinogen

A

proenzyme

converted to pepsin by HCl in stomach

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24
Q

what does HCl do to make proteins more susceptible to enzymes in the stomach

A

unravels the proteins

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25
Q

what enzyme releases proenzymes into the small intestine for digesting proteins

A

pancrease

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26
Q

what are the proenzymes of the small intestine

A

trypsinogen
chymotrypsin
procarboxypeptidase A and B
proelastase

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27
Q

why is trypsinogen so important

A

cleaved to trypsin by enteropeptidase

trypsin essential for peptide breakdown because activates all the other proenzymes of the intestine

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28
Q

enteropeptidase

A

brush border enzyme

cleaves trypsinogen to trypsin

29
Q

oligosaccharides are broken down into disaccharides by

A

dipeptidylaminopeptidase

30
Q

disaccharides to AA by

A

amino peptidase

31
Q

two transporters for amino acids

A

Na dependent: brush border

Na independent: basolateral membrane

32
Q

how does Na dependent transport work

A
  1. Na/K pump maintains Na gradient
  2. Na goes into cell and H+ goes out
  3. creates gradient for H+
  4. H+ want to diffuse into cell and bring peptides in with it
  5. peptidases in cytoplasm can further breakdown peptides to AAs if need be
  6. diffuse into blood (passive)
33
Q

what is the Na independent transporter

A

AA to the blood across basolateral membrane

passive diffusion

34
Q

protein degraded by

A

HCl and proteases

35
Q

how are all proteases released

A

proenzymes

36
Q

need enzymes for breakdown of peptides in two different parts of intestine to be sufficient

A

luminal peptidases

brush border enzymes

37
Q

transporters can move proteins across apical membrane in what form(s)

A

peptides (di, tri)

AAs

38
Q

fat breakdown is triggered by

A

lipase

39
Q

three types of lipase

A

lingual
gastric
pancreatic

40
Q

first place lipase is secreted

A

lingal lipase

von ebner’s glands

41
Q

which lipase is most important

A

pancreatic lipase

42
Q

where does fat breakdown start

A

stomach

43
Q

why does chyme stay in stomach for longer period of time

A

chemoreceptors sense FAs

44
Q

why does the stomach mix chyme

A

so that SA increases that lipases can interact with

45
Q

fat has two layers

A

fatty layer

aqueous layer

46
Q

structure of bile salt

A

polar region and non polar region so interacts with both layers of emulsion droplet

47
Q

how does lipase interact with the fat

A

colipase integrates into fat droplet

has polar and non polar region so now lipase can interact with triglyceride

48
Q

how do micelles enhance absorption of FAs

A

micelles are in equilibrium with free FAs

micelles are constantly breaking down and reforming

49
Q

what form of fats are found in systemic circulation

A

triglycerides

50
Q

how are fatty acids absorbed into the cell

A

monoglycerides

51
Q

what happens when monoglycerides enter the endoplasmic reticulum of the cell

A

reform triglycerides

52
Q

what form must triglyceride have to travel accross epithelial cell and be absorbed by lacteal

A

form chylomicron

53
Q

fat soluble vitamins

A

A, D, E, K

54
Q

how are fat soluble vitamins released into the body

A

with chylomicrons

55
Q

the rest of vitamins besides A, D, E, K are water soluble vitamins except

A

vitamin B12

56
Q

how does B12 get into the cell

A

binds to intrinsic factor (IF) and IF will bind to its receptor and taken into cell by receptor mediated endocytosis

57
Q

where does most water absorption occur

A

SI

58
Q

where is Na absorbed in GI tract

A

throughout the entire GI tract

59
Q

what ions do Na help to be absorbed

A

K, Cl, HCO3-

60
Q

where is Na concentration the highest

A

where glucose, galactose, or AA are being transported

61
Q

why do Ca not create salts in the stomach

A

low pH keeps Ca soluble

62
Q

why is there a problem when Ca2+ enters the cell

how do we fix the probelm

A

not acidic environment so Ca2+ will want to produce salts rapidly

calbindin binds to Ca2+ and takes it to basolateral membrane where it can be release into the blood

63
Q

what causes rickets

A

vitamin D deficiency

cant absorb Ca2+

64
Q

what does vitamin D do for Ca2+ absorption

A

increase Ca2+ transporters and binding proteins (calbindin)

65
Q

what state is iron absorbed and what state is iron most present in the body

A

iron absorbed in ferrous state (Fe++)

most iron in body is ferric iron (Fe+++)

66
Q

how do you convert ferric iron to ferrous iron

A

iron reductase

67
Q

what happens first to ferrous iron once it gets into the cell

A

converted back to ferric iron by feroxidase

68
Q

what are the two pathways in the cell that iron can take

A

RELEASED: bind to carrier protein and moved to basolateral membrane to diffuse into blood

STORE: bind to ferritin; inhibits release

Physiology Exam 3 (7 decks)

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