secretions in the stomach

Question 1

functions of the stomach

Answer 1

• stores food - compliant
• kills bacteria - acid
• liquefies food
• mixes chyme with gastric secretions
• kneading of food particles to <1mm
• regulates chyme release into duodenum
• produces intrinsic factor
• very little digestion (proteins) and absorption (alcohol, aspirin) takes place in the stomach

Question 2

what is HCl production is stimulated by

Answer 2

gastrin
ACh
histamine

Question 3

what is ACh

Answer 3

acetylcholine

Question 4

acid/hcl stimulartion full explanation

Answer 4

• HCl production is stimulated by

-gastrin

-ACh = acetylcholine

-histamine

• stimulate parietal cells to secrete HCl
• increase in H+/K+ATPases and Cl- channels on parietal cells
• energetically expensive process (ATP) - 1532Cals/litre secreted - so have lots of mitochondria in the cells to produce ATP

Question 5

when the parietal cells are stimulated what is released

Question 6

desrcibe a resting parietal cell

Answer 6

unstimulated
lots of mitochondria - uses lots of energy
lots of tubulovesicles - H+/K+ ATPase or proton pumps - increase SA when acid needs to be secreted

Question 6

resting parietal cell is ….

Answer 6

unstimulated

Question 7

secreting parietal cell is …..

Answer 7

stimulated

Question 8

secreting/stimulated parietal cell explanation

Answer 8

histamine, gastrin and ACh signal tubulovesicles to come together to produce canaliculi = increase cell surface area ready for acid secretion and insert proton pumps on the surface

Question 9

how are stimulatory singals delivered to the pariental cell to induce HCl secretion

Answer 9

• histamine released from neighbouring gastric ECL cell
• gastrin released from stomach G-cells into blood
  
  • comes back to stomach and stimulates parietal cell
• ACh released from neurones of vagus nerve

Question 9

acid stimulation - what does the receptor have to be for binding

Answer 9

complimentary shape

Question 10

what are the 3 phases of acid secretion

Answer 10

cephalic
gastric
intestinal

Question 11

describe the cephalic phase

Answer 11

entirely neural phase
thought, sight, smell or approach of food leads to ACh release
from vagus
chewing/swallowing can do this too

Question 12

describe the gastric phase

Answer 12

once food is in the stomach - distend it
detected by mechanoreceptors
leads to ACh release
roducts of protein digestion (peptides/AA’s) in stomach = detected by chemoreceptors - lead to gastrin release

Question 13

describe the intestinal phase

Answer 13

primarily acid inhibitory phase
once food enters duodenum
HCl secretion needs to be stopped
presence of HCl in duodenum leads to somatostatin, secretin + CCK
all 3 = inhibit acid secretion from parietal cell
secretin stimulates HCO3- release from pancreas = neutralises acid entering duodenum
CCK = stimulated by lipids entering duodenum
can stimulate digestive enzyme + bile release from pancreas + gallbladder

Question 14

peptic ulcer treatments

Answer 14

H2 - receptor antagonists
-block action f histamine receptor
-cimetidine, ranitidine

PROTON PUMP INHIBITORS
-block ATP driven H+/K+ exchange
-more effective than H2-R antagonists
-omeprazole, lansoprazole

Question 15

the stomach can cope with large acid environment but what can’t

Answer 15

oesophagus and small intestine

Question 16

what does reflux do to teeth

Answer 16

corrodes them

Question 17

what dies acid attacking teeth lead to

Answer 17

high sensitivity rate
lots of caries
lose vertical dimension - become shorter

Question 18

helicobacter pylori

Answer 18

• bacterium strongly associated with PUD
• linked with gastric cancer
• rate of re-infection after antibiotics is high
• route of transmission unclear - oral-oral?
• may survive on dental plaque
• dentists may be at greater risk of infection
• dentists may aid transmission

Question 19

how does the alkaline tide happen

Answer 19

lots of HCO3- from parietal cells into blood after meals
disturbs plasma buffer system
mops up circulating H+ = increase plasma pH
detects temporary rise in pH - alkaline tide

Question 20

what mops up the H+ in the alkaline tide

Answer 20

HCO3-

Question 21

what is HCO3-

Answer 21

bicarbonate

Question 22

what stimulates acid secretion

Answer 22

Ach
gastrin
histamine

Question 23

Ach

Answer 23

neurocrine Vagus

Question 24

gastrin

Answer 24

endocrine gastrin G-cells

Question 25

paracrine

Answer 25

gastric ECL-cells

Question 26

somatostatin

Answer 26

paracrine gastric D-cells

Question 27

secretin

Answer 27

endocrine duodenal S-cells

Question 28

CCK (cholecystokinin)

Answer 28

endocrine duodenal I-cells

Question 29

somatostatin -> pancreas

Answer 29

HCO3- release

Question 30

CCK -> pancreas

Answer 30

enzyme release

Question 31

CCK -> gallbladder

Answer 31

bile release

Question 32

what substance do G cells secrete

Answer 32

gastrin -stimulates acid

Question 33

what substance do D cells secrete

Answer 33

somatostatin -inhibits acid

Question 34

what substance do chief cells secrete

Answer 34

pepsin - ogen gastric lipase

Question 35

what substance do enterochromaffin-like cells secrete

Answer 35

histamine -stimulates acid

Question 35

what substance do mucous neck cells secrete

Answer 35

mucus (protects lining) bicarconate

Question 36

what substance do parietal cells secrete

Answer 36

gastric acid - HCl intrinsic factors (Ca++ absorption)

Question 37

what does gastrin stimulate

Answer 37

acid

Question 38

what does mucus do

Answer 38

protects lining

Question 39

what does histamine stimulate

Answer 39

acid

Question 40

what does somatostatin do

Answer 40

inhibits acid

Question 41

what is the secreting cell for mucus/HCO3-

Answer 41

goblet cells - surface and mucous neck cells

Question 42

what is the secreting cell for acid

Answer 42

parietal cells

Question 43

what is the secreting cell for pepsinogen

Answer 43

chief (zymogen)

Question 44

what is the secreting cell for histamine

Answer 44

enterochromaffin-like

Question 45

what is the secreting cell for gastrin

Answer 45

G cells

Question 46

what is the secreting cell for somatostatin

Answer 46

D cells

Question 47

what is the secreting cell for intrinsic factor

Answer 47

parietal

Question 48

function of mucus/HCO3- /goblet cells

Answer 48

neutralises acid at the lining of stomach = prevents damage to the stomach wall

Question 49

function of acid / parietal cells

Answer 49

mechanical digestion- denatures proteins converts pepsinogen into pepsin = denatures + digests proteins (15%) - chemical digestion converts poorly absorbed ferric iron (Fe3+) ion into absorbable ferrous iron (Fe2+) - iron deficiency anaemia without acid

Question 50

function of pepsinogen / chief cells

Answer 50

start protein digestion in the stomach

Question 51

function of histamine/enterochromaffin-like

Answer 51

stimulate acid secretion from parietal cells

Question 52

function of gastrin/G cells

Answer 52

stimulate acid + secretion from parietal cells stimulates ECL cells to release histamine

Question 53

function somatostatin/D cells

Answer 53

inhibit acid secretion from parietal cells

Question 54

function of intrinsic factor/parietal cells

Answer 54

add absorption of vitamin B12 from ileum- vit.B12 essential for RBC maturation - pernicious anaemia without intrinsic factor