L3- Stomach secretions

Question 1

functions of the stomach

Answer 1

• store food
• regulates the release the contents into the duodenum
• mix the food with the gastric secretions

Question 2

what is the inner lining called in stomach and in other organs

Answer 2

mucosa

Question 3

function of mucous neck cell

Answer 3

• mucous neck cell- produces mucous and bicarbonate fluid to protect from injury and acid erosion

-

Question 4

function of parietal cell

Answer 4

secretes acid and intrinsic factor ( for absorbing food)

-predominantly found in the corupus region

Question 5

function of chief cell

Answer 5

secretes pepsinogen whhich is a precursor for pepsin

- predominantly found in the corupus region

Question 6

function of ECL like cells

Answer 6

secretes histamine to trigger acid secretion

- in corpus region

Question 7

function of d cells

Answer 7

secretes somatostatin for acid secretion

-found in corupus, antrum and pylorus region of the stomach

Question 8

function of G cells

Answer 8

secretes gastrin for acid secretion

- found in antrum and pylorus region of the stomach

Question 9

what happens when a parietal cell is stimulated

Answer 9

• CO2 diffuses into the cell
• joins with water to make carbonic acid caytalsed by carbonic anhydrase
• the acid dissociates into H+ ion and HCO3-
• HCO3 transported out into the blood in exchange of CL- ions, resulting in alkaline tide in the plasma
• H ions transported out into the lumen in exchange for K+ ions through ATPase.
• now the acid is produced in the lumen

Question 10

how does gastrin regulates acid secretion

Answer 10

• gastrin - stored in vesicles along the basolateral membrane of the cell and gets released through vagal stimulation
• increases expression of protom pumps in the parietal cells in the antrum
• gastrin binds to ecl cell to stimulate histamine synthesis and the histaine act upon the H2 receptors on pareital cells to release acid

Question 11

what part of the nervous systems control the functions of the stomach

Answer 11

• ENS through vagus and sympathetic nerves

Question 12

how can ACH act upon acid secretion

Answer 12

• stimulates parietal cells to release acid and G cells to release gastrin
• stimulates ECL cells to release histamine
• stimulates D cells to inhibit somatostatin release

– ACH stimulates G cells which then stimulates parietal cell directly and indirectly via ECL cell

Question 13

triggers for acid secretion

Answer 13

gastrin, histamine, ACH,

Question 14

inhibitory factors for acid secretion

Answer 14

• somatostatin
• CCK
• secretin
• VIP and GIP

Question 15

how does secretin act upon the acid secretion inhibition

Answer 15

• inhibits gastrin release and acid secretion

- stimulated by the acid in the duodenum

Question 16

how does somatostatin act upon the acid secretion inhibition

Answer 16

• due to high levels of gastrin in the blood, the somatostatin is released from the d cells
• inhibits gastrin from G cells and histamine secretion from ECL cells

Question 17

how does VIP and GIP act upon the acid secretion inhibition

Answer 17

acts on the same receptors for secretin on the parietal cells to stop acid release

Question 18

how does CCK act upon the acid secretion inhibition

Answer 18

• produced by I cells in the duodenum and jejunum in response to fat.
• reduces acid release from parietal cells by acting as an antagonist for the acid secretion

Question 19

pharmacoloigcal inhibitors for acid secretion

Answer 19

• proton pumps inhibitors

- H2 receptors anatagonists which are competitive against histamines at the parietal cells receptors

Question 20

4 phases of gastric acid secretion

Answer 20

-basal, cephalic, gastric, intestinal

Question 21

what is basal phase

Answer 21

where the acid secretion follows circadian rhythm

• so its low at a.m and high at p.m
• enchanced even higher by eating

Question 22

what is cephalic phase

Answer 22

a response to an approach of food before it reaches the mouth like by smell, sight, taste, thought.
-gastric acid and pepsinogen activated

Question 23

what is gastric phase

Answer 23

when the food enters the stomach
- more than 50% acid secretion
-

Question 24

what is intestinal phase

Answer 24

food mixed with secretions from pancreas and liver

• gastrin secretion and gut motility inhibited
• acidic fluid in the small intestine from the stomach cause a release of secretin and other factors inhibit acid secretion

Question 25

why is it important to inhibit acid secretion once the food enters the duodunum

Answer 25

• digestive enzymes requires neutral or near acidic Ph for optimum activity
• micelle formation for fat digestion and absorption can take place at neutral or near acidic pH
• reduces risks for ulcers

Question 26

what does pepsinogens do in the digestion

Answer 26

initiates protein digestion

Question 27

why is prostaglandins helpful protecting gastric muscosa

Answer 27

• inhibits acid secretion
• stimulates HCO3 release to neutralise the acid
• secretes mucus

Question 28

what does H pylori do

Answer 28

produces urease

• converts urea into other products then into HCO3 and NH4+
• the HCO3 neutralises the stomach acid

Question 29

what happens if there is H.p infection in the antrum

Answer 29

• G cells secretes gastrin too much
• and decrease somatostatin release
• so too acid is produced
• this is hypergastrinaemia

Question 30

what happens if there is H.p infection in the corpus

Answer 30

• gastric ulcers and reduces acid secretion
  so there is a loss of acid
• this is hypochlorhydria

Question 31

why is intrinic factor important

Answer 31

• produced by the parietal cells

- important to absorb Vit B12 otherwise results in health consequences