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Physiology III > Lecture 23: Mucosal Digestion > Flashcards

Lecture 23: Mucosal Digestion Flashcards

1
Q

Absorption refers to the…

A

Transfer of simple molecules across intestinal epithelium

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2
Q

Maldigestion is usually related to a ___ problem whereas malabsorption is related to a ___problem

A

Enzyme, epithelial

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3
Q

What is are four ways to increase surface area of GI

A
  1. GI tract elongation
  2. Plica circulars
  3. Villi
  4. Microvilli
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4
Q

What is the glycocalyx

A

Border of glycoproteins on apical membrane of enterocytes

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5
Q

What structures create the mucosal border

A

Microvilli, glycocalyx, mucus, unstirred water

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6
Q

What does enteritis do to the villi

A

Destroys villi resulting in loss of absorptive surface/malabsorption

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7
Q

What are the two phases of carbohydrate digestion

A

Luminal and membranous

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8
Q

What happens during luminal phase of carbohydrate digestion

A
  1. Breakdown facilitated by enzymes of salivary gland and pancreas
  2. Polysaccharides broken down to dimers and trimers
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9
Q

Where are enzymes bound during membranous phase

A

Glycocalyx (diffused through mucus layer)

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10
Q

What happens during membranous phase of carbohydrate digestion

A

Dimers and trimers are broken down by sugar specific enzymes to monomers and then absorbed

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11
Q

What enzyme hydrolyzes starches to smaller polysaccharides in the oral cavity

A

Alpha-amylase

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12
Q

In the stomach 30-40% of starches are converted to ___

A

Maltose

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13
Q

What enzyme further breaks down all starches to di or polysaccharides

A

Alpha-amylase

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14
Q

What di or polysaccharides are the result of carbohydrate digestion in SI

A

Maltose, isomaltose, dextrin and maltotriose

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15
Q

What are two forms of starches

A

Amylose and amylopectin

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16
Q

Carbohydrate polymers come as __, ___, ___ or ___

A

Fibers, starch, sugar, glycogen

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17
Q

T or F: fibers are indigestible by mammals

A

True

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18
Q

What bond makes fiber indigestible by mammals

A

Beta-acetal bond between carbons 1 and 4

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19
Q

How are fibers digested

A

Fermenting bacteria in hind or foregut depending on species

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20
Q

Where does fiber come from in plants

A

Cell wall

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21
Q

Where does sugar come from in plants

A

Vacuoles

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22
Q

Where does starch come from in plants

A

Endosperm

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23
Q

Fiber remains in the lumen and provides bulk to ___

A

Feces

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24
Q

Bacterial hydrolyzes in rumen and/pr cecum/colon ferment fiber to __

A

VFA’s

25
Q

Describe the luminal phase of protein digestion

A

Broken down to peptides and amino acids, first in stomach via gastric enzymes and HCl and then by pancreatic enzymes in duodenum

26
Q

Describe the membranous phase of protein digestion

A

Further breakdown to amino acids facilitated by peptidases

27
Q

Proteins are hydrolyzed into __, ___ and ___

A

di, tripeptides and AS

28
Q

Gastric pepsinogen is activated by __ and ___

A

HCl and pepsin

29
Q

Trypsinogen is activated by ___ or ___

A

Enterokinase or trypsin

30
Q

Trypsin activates __

A

Other pro enzymes

31
Q

How does protein absorption differ from carbohydrate absorption

A

Proteins can be absorbed as di, tripeptides or amino acids whereas carbohydrates must be broken down to monomers

32
Q

what cleave internal bonds in proteins

A

Endopeptidases

33
Q

What cleaves terminal residue of polypeptide chain

A

Exopeptidases

34
Q

What cleaves the N-terminal residue on proteins

A

Aminopeptidases

35
Q

What cleaves the C terminal residue on proteins

A

Carboxypeptidases

36
Q

During lipid digestion triglycerides are hydrolyzes into__ and ___

A

Monoglycerides and FFA

37
Q

T or F: fats are water soluble

A

False

38
Q

How does the stomach assist in fat digestion

A
  1. Initial emulsification (coat in bile acids)
  2. Fat globules liquify
  3. Lipid droplets
39
Q

How does the small intestine participate in fat digestion

A
  1. Emulsification finalized
  2. Bile acids and phospholipids added
  3. Emulsified droplets are digested
  4. Co-lipase and lipase produce FFA and monoglycerides
40
Q

What are the four steps of fat digestion in small intestine

A
  1. Emulsification
  2. Hydrolysis of triglycerides
  3. Micelle formation
  4. Micelle content can be absorbed in jejunum
41
Q

What is emulsification

A

Coating lipids in bile acids to make them more hydrophilic

42
Q

What are primary bile acids synthesized by

A

Liver

43
Q

What are secondary bile acids a result of

A

Bacterial actions in the colon

44
Q

What do small lipid droplets encoated in bile acids contain

A

Triglycerides, cholesterol, cholesterol esters, phospholipids

45
Q

Describe the steps in hydrolysis of triglycerides

A
  1. Co-lipase clear bile from surface of droplets
  2. Lipase hydrolyzes triglycerides producing monoglycerides and FFA
46
Q

What are Micelles

A

Small sized droplets that combine with bile salts and phospholipids to prepare for absorption

47
Q

Micelles act as lipid ___ and increase ___ in chyme

A

Lipid shuttles, increase lipid solubility in chyme

48
Q

What part of the small intestine are lipids exposed to bile and form droplets

A

Duodenum

49
Q

What part of small intestine are does co-lipase and lipase act

A

Jejunum

50
Q

What part of small intestines do Micelles diffuse through

A

Jejunum

51
Q

What is exocrine pancreas insufficiency

A

Insufficient synthesis and secretion of pancreatic enzymes caused by pancreatic Acinar atrophy or tumor

52
Q

How does exocrine pancreas insufficiency cause anorexia/exercise intolerance/weakness

A

Insufficient breakdown of nutrients and therefore prevents absorption

53
Q

How does exocrine pancreas insufficiency cause abdominal pain

A

Bacterial gas production/ malfermentation in LI, inflammation

54
Q

How can exocrine pancreas insufficiency cause vomiting

A

Delayed gastric emptying, SI distention due to increase gastric secretion, bacterial toxins in LI

55
Q

How can exocrine pancreas insufficiency lead to diarrhea

A

Osmotic diarrhea

56
Q

How can exocrine pancreas insufficiency lead to dehydration

A

Insufficient water reabsorption in LI

57
Q

How can exocrine pancreas insufficiency lead to fever

A

Bacterial toxins; compromised immune defense

58
Q

How can exocrine pancreas insufficiency cause arrhythmias

A

Electrolyte imbalance, acid-base imbalance

Physiology III (34 decks)

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