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Physiology III > Mucosal Digestion > Flashcards

Mucosal Digestion Flashcards

1
Q

define digestion

A

breakdown of complex nutrient molecules

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2
Q

define absorption

A

transport of simple molecules across intestinal epithelium

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3
Q

simple molecules are absorbed through ___ membrane and are transferred through ___ membrane

A

apical
basolateral

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4
Q

maldigestion and malabsorption cause ___ symptoms but require ___ treatment approaches

A

similar symptoms
different Tx

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5
Q

a lot of enzymatic digestion and all absorption takes place on ___ of intestinal epithelium

A

surface

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6
Q

what are the barriers that nutrients must pass across before being taken up by blood or lymph?

A

unstirred layer
glycocalyx
cell membrane
enterocyte cytoplasm
basolateral membrane
intercellular space
basement of membrane
capillary/lymph membrane

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7
Q

a ___ surface facilitates membrane bound digestion and absorption

A

large

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8
Q

what are the four levels that surface is extended at in SI?

A
  1. GI elongation
  2. plica circulares (mucosal folds)
  3. villi (epithelial projections)
  4. brush border (microvilli)
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9
Q

what is glycocalyx?

A

layer formed by apical membrane covered in glycoproteins that are synthesized in enterocytes and transferred to apical surface

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10
Q

what makes up the mucosal barrier?

A

microvilli/glycocalyx
mucus
unstirred water

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11
Q

what is enteritis?

A

loss of function due to extreme SA reduction

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12
Q

what are the two phases of CHO digestion?

A

luminal
membranous

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13
Q

describe the luminal phase of CHO digestion

A

enzymes from salivary gland and pancreas
incomplete breakdown

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14
Q

describe the membranous breakdown of CHO digestion

A

brush border digestion
enzymes part of glycocalyx allow diffusion of nutrients through mucus layer before being broken down into monomers

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15
Q

where does luminal phase CHO digestion occur?

A

oral cavity, stomach, SI

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16
Q

explain the luminal phase of CHO digestion in oral cavity

A

a-amylase hydrolyzes starch to smaller polysaccharides

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17
Q

explain the luminal phase of CHO digestion in stomach

A

continues digestion
neutralized by acid when mixing
~40% starches convert to maltose

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18
Q

explain the luminal phase of CHO digestion in SI

A

pancreatic a-amylase (more powerful than saliva)
further breakdown

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19
Q

what are the products of starch from luminal phase?

A

amylose and amylopectin become di/tri-mers

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20
Q

explain the membranous phase of digestion of CHO

A

di/tri-meric sugars are broken down into monomers

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21
Q

final breakdown during membranous digestion occurs near site of absorption, which is…

A

apical membrane of absorptive cells

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22
Q

CHO polymers come as…

A

fiber, sugar, starch, glycogen

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23
Q

what is fiber?

A

vegetal origin
indigestible by mammals
beta-acetal bond between C1 and C4
digested by fermenting bacteria

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24
Q

what are sugars?

A

animal and vegetal origin
short molecules (sucrose, lactose)

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25
Q

what are starches?

A

vegetal origin
large molecules (a-acetal bond between C1 and C4

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26
Q

what is glycogen?

A

animal origin
large molecule

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27
Q

plant material provides…

A

fiber, sugar, starch

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28
Q

the polymers of fiber ___ be degraded by luminal or mucosal hydrolases in SI

A

CANNOT

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29
Q

what does fiber do when in GI tract?

A

fiber stays in lumen and provides bulk to feces
helps retain fluid and aids in passage

30
Q

what does the rumen do to fiber?

A

converts to VFA

31
Q

what are the two phases of protein digestion?

A

luminal
membranous

32
Q

explain the luminal phase of protein digestion

A

breakdown to peptides and aa
starts in stomach by gastric enzymes and HCl
completed in duodenum by pancreatic enzymes

33
Q

explain the membranous phase of protein digestion

A

further breakdown to aa
facilitated by peptidases in apical membrane of enterocytes

34
Q

many protein enzymes are ___ for peptide bonds between specific types of aa

A

specific

35
Q

what activates gastric pepsinogen?

A

HCl and pepsin

36
Q

intestinal enzyme are released as ___

A

proenzymes

37
Q

how is trypsinogen activated?

A

enterokinase/trypsin

38
Q

what do endopeptides do?

A

cleave internal bonds

39
Q

what do exopeptidases do?

A

cleave terminal residue of polymer chain

40
Q

what do aminopeptidases do?

A

cleave N terminal residue

41
Q

what do carboxypeptidases do?

A

cleave C terminal residues

42
Q

in lipid digestion, triglycerides are hydrolyzed into…

A

monoglycerides and FFA

43
Q

are fats water soluble?

A

NO

44
Q

are lipolytic enzymes water soluble?

A

YES

45
Q

lipids make a ___ portion of diet

A

large

46
Q

fat digestion in oral cavity

A

minimal initial digestion
lipase

47
Q

fat digestion in stomach

A

initial emulsification
fat globules liquify
lipid droplets

48
Q

fat digestion in SI

A

emulsification is finalized
bile acids and phospholipids added
emulsified droplets are digested
pancreatic lipase and co-lipase produce free FA, monoglycerides
cholesterol esterase and phospholipase produce free FA, cholesterol, lyso phospholipid

49
Q

which lipases produce free fa, monoglycerides?

A

cholesterol lipase
co-lipase

50
Q

fat digestion in micelle formation

A

all digestion products surrounded by bile acids

51
Q

what are the 4 steps of fat digestion in SI?

A
  1. emulsification by bile salts
  2. hydrolysis of triglycerides
  3. micelle formation
  4. micelle content absorbed in jejunum
52
Q

what are primary bile acids?

A

synthesized by liver
some are conjugated with taurine or glycine in liver

53
Q

what are secondary bile acids?

A

result of bacterial actions in colon

54
Q

describe the emulsification by bile salts process

A

exposure to bile acids from liver/gallbladder and formation of bile encoated droplets
small droplets have triglycerides, cholesterol, esters, phospholipids
hydrophilic domains allow contact with lipase

55
Q

what cooperates to access bile-coated droplets?

A

pancreatic lipase
co-lipase

56
Q

describe hydrolysis of triglycerides

A

co-lipase clears bile constituents from area of surface to droplet
lipase hydrolyzes triglycerides producing FFA, monoglycerides

57
Q

what are micelles?

A

small sized droplets containing FFA and bile acids

58
Q

describe the process of micelle formation

A

products of hydrolytic lipid digestion combines with bile salts and phospholipids to form micelles in preparation for absorption

59
Q

micelles act as lipid ___ and ___ lipid solubility in chyme

A

shuttles
increase solubility

60
Q

micelle content can be absorbed in…

A

jejunum

61
Q

nutritional differences between and within species are reflected by…

A

digestive intestinal activity

62
Q

activities of digestive enzyme often ___ levels of substrate in diet

A

match

63
Q

what is exocrine pancreas insufficiency (EPI)?

A

insufficient synthesis and secretion of enzymes from 90% of pancreas
caused by pancreatic acinar atrophy or tumor

64
Q

what are symptoms of exocrine pancreas insufficiency?

A

anorexia, V, exercise intolerance, D, abdomen pain, dehydration

65
Q

why does exocrine pancreas insufficiency cause D?

A

water follows solutes

66
Q

why does exocrine pancreas insufficiency (EPI) anorexia and exercise tolerance?

A

insufficient breakdown of nutrients that prevents absorption

67
Q

why does exocrine pancreas insufficiency (EPI) abdomen pain?

A

bacterial gas production and malfermentation in LI

68
Q

why does exocrine pancreas insufficiency (EPI) cause V?

A

due to delayed gastric emptying
SI distension
bacterial toxins in LI

69
Q

why does exocrine pancreas insufficiency (EPI) cause D?

A

osmotic D

70
Q

why does exocrine pancreas insufficiency (EPI) cause dehydration?

A

insufficient water absorption in LI

since water follows solute (so stays in GI tract)

71
Q

why does exocrine pancreas insufficiency (EPI) cause fever?

A

bacterial toxins, compromised immune defense

Physiology III (18 decks)

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