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buzzywords > Gi physiology > Flashcards

Gi physiology Flashcards

1
Q

what do chief cells do

A

Release inactive pepsinogen -> pepsin which breaks down protein

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2
Q

what do parietal cells do

A

Intrinsic factor – for absorption of B12

HCl – denatures proteins and kills microorganisms

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3
Q

what increases stomach emptying

A
  • Increased volume of chyme [increased distension]
  • Decreased viscosity of chyme [thinner]
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4
Q

what decreases gastric emptying

A

Fat decreases gastric emptying as more time required for digestion.

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5
Q

what stimulates and is the action of Gastrin

A
  • peptides/ amino acids in stomach
  • increases secretion and promotes intestinal contraction
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6
Q

what stimulates and is the action of Ghrelin

A

fasting state
- stimulates hunger and satiety

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7
Q

what stimulates and is the action of histamine

A

food in stomach
- Stimulates parietal cells H+/K+ATPase to release HCl

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8
Q

what stimulates and is the action of serotonin

A

food in stomach
- decreases secretions and gastric movement

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9
Q

what stimulates and is the action of somatostatin

A

food in stomach
- decreases secretions and reduces intestinal absorption

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10
Q

what stimulates secretions

A

Ach

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11
Q

what inhibits secretions

A

somatostatin

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12
Q

what does prostaglandin E do (PGE2)

A

reduces histamine and increases mucus / bicarbonate secretion

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13
Q

where are gastrin and somatostatin secreted

A

at the pyloric antrum

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14
Q

describe the mucosal barrier to the stomach

A
  1. Stomach wall coated by thick wall of bicarbonate-rich mucus
  2. Epithelial cells meet at tight junctions preventing gastric juice from penetrating
    underlying tissue layers
  3. Stem cells replace damaged epithelial mucosal cells (completely replaced every 3-6
    days)
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15
Q

what does the presence of chyme in the duodenum do

A

activates receptors that inhibit gastric secretion

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16
Q

adapted for absorption as increase in surface area due to:

A
  • Circular folds
  • Villi – lymphatic vessels [lacteals]
  • Microvilli – brush border
17
Q

what does the duodenum mucosa have

A

Brunner’s glands

18
Q

Extrinsic innervation of the small intestine:

A
  • Parasympathetic nerve fibres from vagus nerve
  • Sympathetic nerve fibres from thoracic splanchnic nerve
19
Q

describe gastrin

A

released by G cells
- stimulates secretion of bile and pancreatic enzymes

20
Q

describe CCK

A

released by I cells
- stimulates release of pancreatic juices and bile

21
Q

describe secretin

A

released by S cells
- stimulates bicarbonate release from pancreas in response to H+ in duodenum

22
Q

describe motilin

A

released by M cells
- inhibits gastric secretion, stimulates insulin secretion

23
Q

what do CCK and secretin do

A

decrease parietal cell secretion of HCL

24
Q

describe cholecystokinin

A

secreted by I cells
- promotes the contraction of the gallbladder, increasing the secretion of the bile into the duodenum at the ampulla of vater

25
Q

describe Leptin

A

a hormone secreted by adipose tissue that promotes satiety
- genetic defect in leptin signalling may cause monogenic obesity

26
Q

what is somatostatin secreted by

A

D cells

27
Q

what does secretin do

A

decrease gastric acid secretion

28
Q

what are acinar cells

A

digestive enzymes

29
Q

what does trypsin do

A

activate all other protein enzymes

30
Q

what is the haustra

A

tonic contractions of taenia coli bunch up into pouches called haustra

31
Q

what does stomach distension do

A

promotes gastrocolic reflex increasing motility in colon

32
Q

what must carbohydrates be converted into for absorption

A

monosaccarides

33
Q

what does amylase do

A

break down a-1,4 linkages as long as they are not terminal

34
Q

what does HCL do

A

denature proteins

35
Q

what does pepsin do

A

cleaves proteins into peptides

36
Q

what do pancreatic enzymes do eg
(trypsin, chymotrypsin, elastase)

A

breakdown proteins into
oligopeptides

37
Q

what do Peptidases at brush border do

A

hydrolyse oligopeptides to amino acids

38
Q

what stabilises the emulsions and how

A

Amphiphilic molecules stabilise the emulsions by forming a surface layer on droplets of fatty
acids, biliary phospholipids, cholesterol, bile salts.

39
Q

what are bile salts

A

Bile salts are amphipathic – hydrophilic and hydrophobic.

They are released from gall bladder in response to CCK and aid in emulsifying lipid droplets.

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