physiology of the stomach 1

Question 1

what are the functions of the stomach

Answer 1

• temp storage of food
• mechanical digestion by stomach movements
• chem digestion of proteins
• regulation of passage of chyme into small intestine
• secretion of intrinsic factor, essential for absorption of vitB12

Question 2

how does mechanical digestion in the stomach work

Answer 2

the muscularis enables food to be churned - particularly in the antrum where the muscle wall is thicker

food mixed with gastric juice to produce chyme, chyme passes through pyloric sphincter to duodenum

Question 3

what are the three types of cells that together produce gastric juices

Answer 3

• zymogenic (chief/peptic) cells
• parietal (oxyntic) cells
• goblet (neck) cells

Question 4

what do zymogenic (chief/peptic) cells do

Answer 4

secrete pepsinogen

Question 5

what do parietal (oxyntic) cells do

Answer 5

secrete HCl (and intrinsic factor)

Question 6

what do goblet (neck) cells do

Answer 6

secrete mucous

Question 7

what are additional cells in gastric glands

Answer 7

• G cells
• Enterochromaffin (mast like) cells
• D cells

Question 8

what do G cells do

Answer 8

secrete gastrin

Question 9

what do enterochromaffic (mast like) cells do

Answer 9

secrete histamine

Question 10

what do D cells do

Answer 10

secrete somatostatin

Question 11

are there parietal cells in the antrum

Answer 11

no

Question 12

what happens during chemical digestion in the stomach

Answer 12

• proteins are broken down by pepsin
• gastric lipase breaks down fat at a higher pH

Question 13

where is pepsin active

Answer 13

only active in acid environment

Question 14

how is pepsin produced

Answer 14

its converted from pepsinogen by HCl

Question 15

what is the link between gastric lipase and breast milk

Answer 15

gastric lipase plays an important role in lipid digestion in infants from breast milk

Question 16

what stops the stomach from digesting itself

Answer 16

the mucosal barrier

Question 17

how does the mucosal barrier work

Answer 17

• tight junctions between mucosal epithelial cells prevents leakage of gastric juice onto underlying tissue
• mucous secreted by epithelial/goblet cells has a higher pH, providing localised neutralisation and physical barrier to acid
• prostaglandins increase mucosal thickness and stimulate bicarbonate production

Question 18

what are the three phases of gastric secretion

Answer 18

• cephalic phase
• gastric phase
• intestinal phase

Question 19

what happens and stimulates the cephalic phase

Answer 19

increased secretion.
drop in blood glucose

stimulated by sight, smell taste, thought of food

Question 20

what happens and stimulates the gastric phase

Answer 20

increased secretion

stimulated by stomach distension due to presence of food

Question 21

what happens and stimulates the intestinal phase

Answer 21

decreased secretion.
presence of fat or low pH in duodenum inhibits gastric secretion

stimulated by digested proteins/fat in the duodenum

Question 22

when is HCl secretion inhibited

Answer 22

once food has left the stomach

Question 23

how does neuronal inhibition of HCl work

Answer 23

• partially digested protein and presence of fat in duodenum combined with low pH from gastric acid inhibit secretion

leads to decrease in parasympathetic stimulation

Question 24

how does hormonal inhibition of HCl secretion work

Answer 24

secretin and cholecystokinin are released from duodenum

other inhibitors include GIP, gastronome, glucagon and VIP

somatostatin release in response to increased HCl

Question 25

how is the antrum able to produce strong contractions

Answer 25

it is thicker

Question 26

where does protein digestion start

Answer 26

in the stomach

Question 27

what do peptic cells secrete

Answer 27

pepsinogen

Question 28

what do oxyntic cells secrete

Answer 28

hydrochloride

Question 29

wha do goblet cells secrete

Answer 29

mucus