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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
D cells
secrete somatostatin stimulated by acid in stomach
26
somatostatin in gastric juice
inhibit gastric acid
27
G cells
secrete gastrin stimulated by ACh/ peptides/ amino acids
28
gastrin
stimulates gastric acid secretion
29
gastric phase
food in stomach gastrin release negative feedback inhibition by acid w somatostatin release
30
ampulla of vater
common entrance of bile duct and pancreatic duct into duodenum
31
pancreatic juice fluid and electrolytes
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
pancreatic enzymes
amylolytic (amylase) proteolytic (trypsin, chymotrypsin, elastase) lipolytic (lipase, phospholipase) nucleolytic (DNAase, RNAase) inactive precursors (zymogens)
33
pancreatic proteases
secreted as zymogens enterokinase activation in intestine trypsin can auto-activate endo/exoproteases amino acid specificity protein digestion intestinal peptidases
34
pancreatic HCO3- secretion
acinar cell primary secretion (isotonic NaCl secretion) duct HCO3- secretion (isotonic via apical HCO-Cl exchange and CFTR channels)
35
cystic fibrosis
lack of CFTR channels and fluid secretion lack of washout enzymes pancreatic damage poor nutrition
36
pancreatic secretion control
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
bile functions
elimination of waste products (cholesterol/ bile pigments/ minerals/ lipophilic drugs and metabolites/ heavy metals) promotion of lipid digestion and absorption
38
bile
hepatocytes secrete bile into canaliculi secrete HCO3- rich fluid enters duodenum by common bile duct stored and concentrated in gall bladder
39
bile composition
biliary lipids (bile acids/ phospholipids/ cholesterol) bile pigments (bilirubin)
40
bile acids
primary> liver synthesis from cholesterol secondary > modification by intestinal bacteria conjugation> to amino acids/ ^solubility/
41
enterohepatic circulation of bile acids
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
emulsification of dietary lipids
^sa exposed to lipases/ digestion promotion bile salts coat lipids
43
gall bladder function
concentrates bile absorbs electrolytes/ water isotonic Na+ w bile salts
44
biliary secretion control
bile acid- dependent ductal > secretin gall bladder contraction> cholecystokinin/ vagal nerves/ integrated w pancreatic enzyme secretion
45
gallstones
failure to keep cholesterol in solution
46
small intestine 3 sections
duodenum ileum jejunum
47
functions of small intestine
digestion nutrient absorption electrolyte absorption water absorption secretion
48
carb digestion/ absorption
luminal digestion of starch-type polysaccharides membrane digestion by disaccharides absorption of monosaccharides in small intestine
49
amylase
endo enzyme that can only break internal bonds can't produce monosaccharides
50
carb absorption
monosaccharides apical membrane > SGLT1 (glucose/ galactose)- Na+ coupled, secondary active transport GLUT5 (fructose) -facilitated diffusion basolateral membrane (GLUT2- basolateral diffusion)
51
protein digestion and absorption
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
protein digestion enzymes
gastric pepsin ~20% pancreatic peptidases membrane and cytosolic peptidases
53
peptide absorption
acid microclimate utilisation followed by cytosolic peptide digestion/ export peptide carrier for drugs (ACE inhibitors, beta lactam antibiotics, prodrugs)
54
amino acid absorption
neutral/ cationic/ anionic transporters apical membrane, coupled to ion uptake/ secondary active transport/ epithelial accumulation facilitated diffusion on basolateral membrane
55
lipid digestion and absorption steps
low water solubility solubilisation digestion absorption re-esterification of fatty acids transport to blood
56
dietary lipids
triglycerides (triesters of glycerol and long-chain fatty acids) phospholipids ( short chain fatty acids
57
lipid digestion stages
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
micelles
5nm polymolecular aggregates monoglyceride/ fatty acids/ bile salts cholesterol and fat-soluble vitamins

PSC1002- Physiology (8 decks)

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