Gastric Function

Question 1

what are the three main tasks of the stomach?

Answer 1

temporary food store (most important)
some degradation of protein and starch - smaller surface area
Hydrochloric acid kills bacteria in food - and enzyme (Pepsin) activation

Question 2

most important stomach function?

Answer 2

temporary food store

Question 3

band of muscle down the pipe of the oesophagus?

Answer 3

sphincter

Question 4

what is almost absent in horses and really small in other species apart from pigs where it is large?

Answer 4

cardia

Question 5

sphincters are?

Answer 5

muscular bands

Question 6

when the stomach is empty, what is maintained?

Answer 6

contraction is maintained = tonic contraction

Question 7

when an animal eats, what happens to the stomach?

Answer 7

the muscles relax = receptive relaxation

Question 8

what is receptive relaxation regulated by?

Answer 8

via vagal fibres

Question 9

what does relaxation allow for?

Answer 9

it allows for increase in stomach content without the increase in pressure - this aids the ‘food storage’ function of the stomach

Question 10

what area of the stomach is the distal stomach referring to?

Answer 10

mainly to pyloric area

Question 11

what does the arrival of waves of depolarisation result in?

Answer 11

large parts of the pylorus wall contracting simultaneously, increasing luminal pressure and forcing chyme through the partially open sphincter

Question 12

type of epithelial on oesophageal sphincter?

Answer 12

stratified squamous

Question 13

why does more active digestion occur in the distal stomach?

Answer 13

due to stronger peristaltic contractions

Question 14

why are larger particles held back in the stomach?

Answer 14

so they can be broken down further

Question 15

what are the 4 types of cells in the crypts/pits of the stomach?

Answer 15

mucin producing
parietal
chief
endocrine

Question 16

what do the mucin producing cells secrete?

Answer 16

mucin

Question 17

‘ogen’

Answer 17

inactive precursors

Question 18

what do parietal cells secrete?

Answer 18

HCl and intrinsic factor

Question 19

what do chief cells secrete?

Answer 19

pepsinogen

Question 20

what do endocrine cells secrete?

Answer 20

G cells secrtee gastrin or ECL cells which secrtee histamine)

Question 21

where is most gastric juice produced?

Answer 21

in the glands of fundus and corpus

Question 22

what do the glands in the cardia region secrete?

Answer 22

only mucus - protective role

Question 23

what do gastric juices consist mainly of?

Answer 23

HCl and pepsinogen

Question 24

what mainly secretes HCl?

Answer 24

mainly from parietal cells

Question 25

what does HCl do to tissue/muscle?

Answer 25

degrades connective tissue and muscle

Question 26

what does HCl do to microorganisms?

Answer 26

kills them

Question 27

carbonic anhydrase>?

Answer 27

enzyme for conversion of co2 and h2o to h2co3

Question 28

after being fed, pH?

Answer 28

increases

Question 29

pepsinogen stored and synthesised by?

Answer 29

chief cells

Question 30

what is pepsinogen?

Answer 30

the inactive form of pepsin

Question 31

what does pepsin do?

Answer 31

degrades feed proteins to peptides

Question 32

type of catalysis that pepsinogen is used in?

Answer 32

autocatalysis role of pepsin

Question 33

what three substances exert stimulatory effects in order to regulate gastric secretion?

Answer 33

ACh gastrin histamine

Question 34

Where is HCl mainly secreted from?

Answer 34

mainly from parietal cells

Question 35

for the regulation of gastric secretion, what three substances exert stimulatory effects?

Answer 35

ACh Gastrin Histamine

Question 36

signals to nervous system good for?

Answer 36

stops overfeeding and over secretion

Question 37

what happens during anticipatory part of secretion?

Answer 37

saliva and vagal nerve stimulation

Question 38

summary of secretion:

Answer 38

saliva + vagal nerve stimu vagal stimu of chief cells - pepsinogen vagal stimulation of parietal cells - HCl stimulation of G cells to release gastrin (+ve feedback on parietal cells and ECL cells) ECL cell stimulation (histamine) drivers further HCl secretion

Question 39

point of mechanoreceptors in stomach?

Answer 39

they detect the stomach wall stretching - drives secretion until feed is complete

Question 40

how is secretion inhibited?

Answer 40

signals from duodenum if pH falls too low - somatostatin release (blocks gastrin release) At start of meal (b4 food reaches stomach) HCl secretion is low but H+ conc high This blocks further acid secretion When animal eats, stomach supplied with buffer (proteins) so [H+] decreased + gastrin is released

Question 41

what happens when the animal is going to eat?

Answer 41

the stomach is supplied with buffer (proteins), [H+] decreases and gastrin is released

Question 42

what happens if pH falls too low?

Answer 42

somatostatin release (blocks gastrin release)

Question 43

level of HCl before food reaches the stomach (at the start of the meal)?

Answer 43

HCl secretion is low but [H+] is high

Question 44

what does low HCl and high [H+] do?

Answer 44

it blocks further acid secretion

Question 45

where is recently swallowed food found?

Answer 45

in the proximal area of the stomach

Question 46

contraction in the proximal area of stomach - strength, meaning?

Answer 46

the contractions are weak so food layers in the order it was eaten - enables enzymes to act before becoming deactivated e.g. amylase for starch

Question 47

describe the food found in the distal portion of the stomach?

Answer 47

it is well mixed with HCl and pepsin

Question 48

gut's own nervous system?

Answer 48

enteric nervous system

Question 49

factors affecting gastric emptying?

Answer 49

expansion of the stomach wall gastrin Distension of duodenum high fat and protein concentrations (requires slower digestion) reduced pH important mediators

Question 50

what does GIP do?

Answer 50

mediates changes in gastric emptying

Question 51

what does secretin do?

Answer 51

stimulated by acidity, increases HCO3 production by pancreas

Question 52

what do the epithelial glands of the abomasum produce?

Answer 52

producing pepsinogen and HCl

Question 53

what do young ruminants produce from the abomasum? what is this used for?

Answer 53

they also produce rennin helps with digestion of milk

Question 54

because the absomasum is not a storage organ - what does it do?

Answer 54

it receives a continuous flow of ruimen content

Question 55

pH of the absomasum?

Answer 55

low pH

Question 56

how is emptying regulated in the abomasum?

Answer 56

the same way as the stomach

Question 57

what does HCl do for the stomach?

Answer 57

degrades connective tissue and muscle and kills microorganisms

Question 58

what does HCl do to pepsinogen?

Answer 58

it transforms pepsinogen (precursor) to pepsin (active enzyme)

Question 59

How is HCl produced?

Answer 59

Produced by: H/K ATP-ase pump which provides the H+ and the HCO3-/Cl- pump which provides Cl-

Question 60

How is HCl produced after a meal?

Answer 60

Production of HCl after a meal requires simultaneous stimulation of parietal cells by all three substances (ACh, gastrin, histamine) Gastrin is released into the blood to stimulate secretion of HCl, pepsinogen and to promote gastric motility Histamine acts as a paracrine hormone, stimulating HCl secretion Vagal reflexed are stimulated by stomach expansion