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a. SL12102: The science of medicines > L23 - GI Digestion And Absorption > Flashcards

L23 - GI Digestion And Absorption Flashcards

1
Q

What is digestion? (2)

A

Sequence by which food is broken down and chemically converted
- to be absorbed by cells of an organism
- used to maintain vital bodily functions

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2
Q

What are the cells involved in the secretion in the salivary glands? (4)

A
  • myoepithelial cells
  • serous cells
  • duct cells
  • mucous cells
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3
Q

What do serous cells secrete? (2)

A
  • amylase
  • lingual lipase
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4
Q

What does amylase do? (2)

A
  • breakdown of carbohydrates
  • brief, inactivated in acidic conditions
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5
Q

What does lingua lipase do? (4)

A
  • breakdown of trigkycerides (fat)
  • optimal at pH 4-5
  • continues throughout GI tract
  • important in newborns
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6
Q

What are the types of cells in the stomach that secrete? (4)

A
  • parietal cell
  • chief cell
  • mucous cell
  • G cell
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7
Q

What do parietal cells do? (2)

A

secretes HCl
- denatures protein
- pepsinogen to pepsin

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8
Q

What do chief cells do? (2)

A

Secrete pepsinogen
- converted to pepsin
- protein digestion

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9
Q

What do mucous cells do? (2)

A
  • protection
  • lubrication
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10
Q

What do G cells do?

A

Produce gastrin
- controls HCl, motility, pepsin, muscous

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11
Q

What is the gastric acid secretion? (2)

A

HCl (~2.5L/day)
- stomach pH 2-3
- optimal for pepsin

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12
Q

What is gastric acid secretion stimulated by? (3)

A
  • histamine
  • gastrin
  • ACh
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13
Q

What is contained within the storage vesicles? (3)

A
  • trypsinogen
  • chymotrypsinogen
  • procarboxypeptidases
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14
Q

What happens to the - trypsinogen, chymotrypsinogen, procarboxypeptidases released?

A

Broken down by eneteropeptidases on the brush border
= activates them

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15
Q

What else is secreted in the pancreatic secretion? (4)

A
  • amylase - starch - active
  • lipase - fat - active
  • RNAase
  • DNAase
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16
Q

What is secreted from the gall bladder?

A

Bile

17
Q

Where is bile formed in, stored and concentrated, and released into? (3)

A
  • liver from cholesterol in diet
  • gallbladder
  • into SI
18
Q

What controls the digestive process? (3)

A
  • Stretch receptors - send signals to brain, triggers secretion of digestive juices
  • Stomach - gastrin, promotes production of stomach acids
  • Intestine - releases secretin and cholecystokinin, stimulates secretion of pancreatic juice and bile
19
Q

What routes of absorption are there? (2)

A
  • Lipids - to lymph lacteal
  • Sugars and a/a - to portal blood supply
20
Q

What are the mechanisms of absorption? (2)

A
  • active transport
  • carrier-mediated (facilitated) transport
21
Q

What is protein digestion?

A

Proteases catalyse hydrolysis of a/a

22
Q

What are the main proteases? (3)

A
  • pepsin in stomach
  • trypsin, chymotrypsin from pancreas
  • peptidases in intestinal brush border
23
Q

Where does protein absorption occur?

A

In the SI
(Active transport of tripeptides, dipeptides and a/a)

24
Q

What is carbohydrate digestion? (3)

A
  • Mouth - begins, salivary amylase
  • Stomach - denatures amylase
  • SI - pancreatic amylase - digested by intestinal brush border enzymes
25
Q

What happens in carbohydrate absorption? (3)

A
  • enzymes on luminal surface of SI epithelial cells digest disaccharides into monosaccharides
  • absorbed by facilitated diffusion or active transport with Na+
  • leave epithelial cells by facilitated diffusion, enter blood, distributed throughout body
26
Q

What is the main site of fat digestion?

A

Small intestine

27
Q

What is fat digestion critically dependent on? (3)

A
  • secretions from the liver and pancreas
  • emulsification required
  • bile and lipase involved from gallbladder and pancrease
28
Q

What are the sequence of steps in fat absorption? (5)

A
  • FA & monoglycerides pass through epithelial cell layer
  • converted to triglycerides
  • combine with cholesterol, phospholipids, protein = chylomicron
  • water soluble, enters lacteal
  • transported from lacteal to bloodstream
29
Q

What occurs at the stomach for oral drug absorption?

A

Disintegration and dissolution
- by acid environment and mechanical churning

30
Q

How is the drug absorbed in oral drug absorption? (3)

A
  • passive diffusion
  • facilitated diffusion
  • active transport
31
Q

What is oral drug absorption determined by? (3)

A
  • physiochemical properties
  • formulation
  • route of administration
32
Q

What is oral drug absorption affected by? (5)

A
  • luminal pH
  • SA
  • perfusion
  • bile
  • mucus
33
Q

What is oral drug absorption influenced by?

A

Intestinal transit time

34
Q

What does enteric coating do? (2)

A
  • prevents formulation from gastric fluid in stomach
  • release drug component in intestinal region
35
Q

What is the enteric coating prepared from?

A

Gastric resistant polymers
- insoluble at low pH

36
Q

What is drug releaae controlled by?

A

pH

37
Q

How does enteric coating help? (4)

A
  • prevents gastric distress/nausea due to irritation
  • protect acid-labile drugs
  • delivers drugs intended for local action at intestine
  • provide delayed release compounds

a. SL12102: The science of medicines (35 decks)

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