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PSC1002- Physiology > gastrointestinal tract L27-29 > Flashcards

gastrointestinal tract L27-29 Flashcards

1
Q

saliva functions

A

lubrication
digestion
solution
moisture
protection

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2
Q

3 types of salivary glands

A

parotid
sublingual
submandibular
*1.5L secretion per day

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3
Q

salivary gland structure

A

acinus> primary secretion
duct> seconadry modification/ low H2O permeability

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4
Q

final saliva

A

isotonic HCO3 rich

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5
Q

salivation control

A

cephalic
parasympathetic
sympathetic

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6
Q

cephalic phase

A

unconditioned/ conditioned
sight/ thought/ smell/ taste of food
vagus efferent nerves direct effect on histamine/ gastrin release

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7
Q

parasympathetic salivary phase

A

cholinergic
cranial nerves VII / IX
(not vagus)
large volume

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8
Q

sympathetic salivary phase

A

smaller volume
rich in enzymes and mucus

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9
Q

gastric functions

A

reservoir
mixing food w gastric secretions
digestion
controlled gastric emptying
protection

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10
Q

gastric juice composition

A

HCl
pepsinogen> pepsin
mucus/ bicarbonate
intrinsic factor
(2L/day)

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11
Q

parietal cells

A

secrete intrinsic factor/ gastric acid
stimulated by histamine/ ACh/ gastrin

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12
Q

gastric acid

A

kills bacteria
activates pepsin
denatures protein

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13
Q

intrinsic factor

A

complexes w vitamin B12 to permit absorption

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14
Q

parietal cell secretion of HCl

A

carbonic anydrase catalyses H+ generation
apical membrane has proton pump/ K+ channels/ Cl- channels
basal membrane has Na+/K+ ATP-ase and Cl-/HCO3 exchange

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15
Q

chief cells

A

secrete pepsin and gastric lipase
stimulated by ACh/ acid/ secretin

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16
Q

pepsin

A

digests proteins
inactivated at pH >3.5 and denatured at pH >7.2

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17
Q

gastric lipase

A

digests fats

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18
Q

mucous neck cells/ surface cells

A

secrete mucus > stimulated by tonic secretion
secrete bicarbonate> stimulated by mucus

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19
Q

mucus in gastric juice

A

physical barrier between lumen and epithelium

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20
Q

bicarbonate in gastric juice

A

buffers gastric acid to prevent epithelium damage

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21
Q

autodigestion prevention

A

gastric mucosal protection
mucus-HCO3 barrier

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22
Q

parietal cell function control

A

direct/ indirect chemical regulators:
histamine from ECL cells
somatostatin from D cells
gastrin from G cells
ACh from vagus and enteric neurones

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23
Q

enterochromaffin-like cells

A

secrete histamine
stimulated by ACh/ gastrin

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24
Q

histamine in gastric juice

A

stimulates gastric acid secretion

25
Q

D cells

A

secrete somatostatin
stimulated by acid in stomach

26
Q

somatostatin in gastric juice

A

inhibit gastric acid

27
Q

G cells

A

secrete gastrin
stimulated by ACh/ peptides/ amino acids

28
Q

gastrin

A

stimulates gastric acid secretion

29
Q

gastric phase

A

food in stomach
gastrin release
negative feedback inhibition by acid w somatostatin release

30
Q

ampulla of vater

A

common entrance of bile duct and pancreatic duct into duodenum

31
Q

pancreatic juice fluid and electrolytes

A

wash out enzymes
~pH 8 alkaline to neutralise gastric acid in duodenum
primary secretion from acinar cells
modified to HCO3- rich juice by duct cells
1.5L / day

32
Q

pancreatic enzymes

A

amylolytic (amylase)
proteolytic (trypsin, chymotrypsin, elastase)
lipolytic (lipase, phospholipase)
nucleolytic (DNAase, RNAase)
inactive precursors (zymogens)

33
Q

pancreatic proteases

A

secreted as zymogens
enterokinase activation in intestine
trypsin can auto-activate
endo/exoproteases
amino acid specificity
protein digestion intestinal peptidases

34
Q

pancreatic HCO3- secretion

A

acinar cell primary secretion (isotonic NaCl secretion)
duct HCO3- secretion (isotonic via apical HCO-Cl exchange and CFTR channels)

35
Q

cystic fibrosis

A

lack of CFTR channels and fluid secretion
lack of washout enzymes
pancreatic damage
poor nutrition

36
Q

pancreatic secretion control

A

secretin > duodenal S cells
release stimulated by acid ^HCO3- secretion
CCK (cholecystokinin-pancreozymin) > duodenal I cell
release stimulated by fat/protein
gall bladder contraction/ pancreatic enzyme secretion stimulation
vagus nerve> stimulates acinar and duct cells

37
Q

bile functions

A

elimination of waste products (cholesterol/ bile pigments/ minerals/ lipophilic drugs and metabolites/ heavy metals)
promotion of lipid digestion and absorption

38
Q

bile

A

hepatocytes secrete bile into canaliculi
secrete HCO3- rich fluid
enters duodenum by common bile duct
stored and concentrated in gall bladder

39
Q

bile composition

A

biliary lipids (bile acids/ phospholipids/ cholesterol)
bile pigments (bilirubin)

40
Q

bile acids

A

primary> liver synthesis from cholesterol
secondary > modification by intestinal bacteria
conjugation> to amino acids/ ^solubility/

41
Q

enterohepatic circulation of bile acids

A

synthesis of primary bile acids in liver (0.6g synthesised per day/ conjugated)
secretion into duodenum in bile
lipid digestion/ absorption
reabsorption in terminal ileum
recirculation through hepatic portal vein to liver
taken up by liver and secreted into bile

42
Q

emulsification of dietary lipids

A

^sa exposed to lipases/ digestion promotion
bile salts coat lipids

43
Q

gall bladder function

A

concentrates bile
absorbs electrolytes/ water
isotonic
Na+ w bile salts

44
Q

biliary secretion control

A

bile acid- dependent
ductal > secretin
gall bladder contraction> cholecystokinin/ vagal nerves/ integrated w pancreatic enzyme secretion

45
Q

gallstones

A

failure to keep cholesterol in solution

46
Q

small intestine 3 sections

A

duodenum
ileum
jejunum

47
Q

functions of small intestine

A

digestion
nutrient absorption
electrolyte absorption
water absorption
secretion

48
Q

carb digestion/ absorption

A

luminal digestion of starch-type polysaccharides
membrane digestion by disaccharides
absorption of monosaccharides in small intestine

49
Q

amylase

A

endo enzyme that can only break internal bonds
can’t produce monosaccharides

50
Q

carb absorption

A

monosaccharides
apical membrane > SGLT1 (glucose/ galactose)- Na+ coupled, secondary active transport
GLUT5 (fructose) -facilitated diffusion
basolateral membrane (GLUT2- basolateral diffusion)

51
Q

protein digestion and absorption

A

gastric/ pancreatic protease luminal digestion
brush-border peptidase membrane digestion
cytosolic digestion in epithelium of small peptides
small intestine absorption > amino acids/ peptides
antigenic quantities of intactv protein

52
Q

protein digestion enzymes

A

gastric pepsin ~20%
pancreatic peptidases
membrane and cytosolic peptidases

53
Q

peptide absorption

A

acid microclimate utilisation
followed by cytosolic peptide digestion/ export
peptide carrier for drugs (ACE inhibitors, beta lactam antibiotics, prodrugs)

54
Q

amino acid absorption

A

neutral/ cationic/ anionic transporters
apical membrane, coupled to ion uptake/ secondary active transport/ epithelial accumulation
facilitated diffusion on basolateral membrane

55
Q

lipid digestion and absorption steps

A

low water solubility
solubilisation
digestion
absorption
re-esterification of fatty acids
transport to blood

56
Q

dietary lipids

A

triglycerides (triesters of glycerol and long-chain fatty acids)
phospholipids (
short chain fatty acids

57
Q

lipid digestion stages

A
  1. emulsification (fat droplets stabilised by bile salts and phospholipids)
  2. digestion (gastric and pancreatic lipases/ co-lipases/ triglycerides to 2 fatty acids and monoglyceride)
  3. diffusion into epithelial cells
  4. re-synthesis of triglycerides
  5. release as chylomicrons
58
Q

micelles

A

5nm polymolecular aggregates
monoglyceride/ fatty acids/ bile salts
cholesterol and fat-soluble vitamins

PSC1002- Physiology (8 decks)

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