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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 __

25
Describe the luminal phase of protein digestion
Broken down to peptides and amino acids, first in stomach via gastric enzymes and HCl and then by pancreatic enzymes in duodenum
26
Describe the membranous phase of protein digestion
Further breakdown to amino acids facilitated by peptidases
27
Proteins are hydrolyzed into __, ___ and ___
di, tripeptides and AS
28
Gastric pepsinogen is activated by __ and ___
HCl and pepsin
29
Trypsinogen is activated by ___ or ___
Enterokinase or trypsin
30
Trypsin activates __
Other pro enzymes
31
How does protein absorption differ from carbohydrate absorption
Proteins can be absorbed as di, tripeptides or amino acids whereas carbohydrates must be broken down to monomers
32
what cleave internal bonds in proteins
Endopeptidases
33
What cleaves terminal residue of polypeptide chain
Exopeptidases
34
What cleaves the N-terminal residue on proteins
Aminopeptidases
35
What cleaves the C terminal residue on proteins
Carboxypeptidases
36
During lipid digestion triglycerides are hydrolyzes into__ and ___
Monoglycerides and FFA
37
T or F: fats are water soluble
False
38
How does the stomach assist in fat digestion
1. Initial emulsification (coat in bile acids) 2. Fat globules liquify 3. Lipid droplets
39
How does the small intestine participate in fat digestion
1. Emulsification finalized 2. Bile acids and phospholipids added 3. Emulsified droplets are digested 4. Co-lipase and lipase produce FFA and monoglycerides
40
What are the four steps of fat digestion in small intestine
1. Emulsification 2. Hydrolysis of triglycerides 3. Micelle formation 4. Micelle content can be absorbed in jejunum
41
What is emulsification
Coating lipids in bile acids to make them more hydrophilic
42
What are primary bile acids synthesized by
Liver
43
What are secondary bile acids a result of
Bacterial actions in the colon
44
What do small lipid droplets encoated in bile acids contain
Triglycerides, cholesterol, cholesterol esters, phospholipids
45
Describe the steps in hydrolysis of triglycerides
1. Co-lipase clear bile from surface of droplets 2. Lipase hydrolyzes triglycerides producing monoglycerides and FFA
46
What are Micelles
Small sized droplets that combine with bile salts and phospholipids to prepare for absorption
47
Micelles act as lipid ___ and increase ___ in chyme
Lipid shuttles, increase lipid solubility in chyme
48
What part of the small intestine are lipids exposed to bile and form droplets
Duodenum
49
What part of small intestine are does co-lipase and lipase act
Jejunum
50
What part of small intestines do Micelles diffuse through
Jejunum
51
What is exocrine pancreas insufficiency
Insufficient synthesis and secretion of pancreatic enzymes caused by pancreatic Acinar atrophy or tumor
52
How does exocrine pancreas insufficiency cause anorexia/exercise intolerance/weakness
Insufficient breakdown of nutrients and therefore prevents absorption
53
How does exocrine pancreas insufficiency cause abdominal pain
Bacterial gas production/ malfermentation in LI, inflammation
54
How can exocrine pancreas insufficiency cause vomiting
Delayed gastric emptying, SI distention due to increase gastric secretion, bacterial toxins in LI
55
How can exocrine pancreas insufficiency lead to diarrhea
Osmotic diarrhea
56
How can exocrine pancreas insufficiency lead to dehydration
Insufficient water reabsorption in LI
57
How can exocrine pancreas insufficiency lead to fever
Bacterial toxins; compromised immune defense
58
How can exocrine pancreas insufficiency cause arrhythmias
Electrolyte imbalance, acid-base imbalance

Physiology III (34 decks)

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