Lecture 8- COPY

Question 1

contents of saliva

Answer 1

EMSL
Electrolytes: hypotonic high HCO3-
Mucins: lubricate bolus and enhance chewing action
Salivary amylase: initiates digestions
Lactoferrin: lysozyme with anti-bacterial action

Question 2

major roles of the stomach

Answer 2

• reservoir
• adjust osmolality of conents
• antrum= grinding
• pylorus= regulates the size of particles
• secretion of acid

Question 3

Gastric motility

Answer 3

1. relaxation of fundus
2. contraction of body and antrum
3. pylorus contracts= to limit exit of chyme
4. mixing by retrupulsion

Question 4

what is required for normal gastric emptying

Answer 4

in tact antrum, pylorus duodenum
normal vagal function
normal hormonal function

(positive feedback from duodenum)

Question 5

what causes delayed gastric emptying

Answer 5

diabetic gastroparesis

• due to autonomic neuropathy
• leads to variable rate of glucose absorption
• upper abdominal discomfort

drugs that delay gastric emptying
- eg anti-cholinergic drugs

Question 6

what causes rapid gastric emptying

Answer 6

after gastric surgery

• “dumping syndrome” = nausea, vomiting, cramping, diarrhoea
• food moves too quickly from stomach to duodenm so are not completely digested
• undigested particles result in hyperosmolar chyme in small bowel
• this causes a rapid fluid shift into the gut causing intestinal distension=pain
• diarrhoea due to osmotic effect

drugs that speed up gastric eptying
- eg metaclopramide

Question 7

what are the 4 types of cells in the stomach

Answer 7

parietal cells
ECL cell
G cell
D cell

Question 8

what is the role of gastric acid in the stomach

Answer 8

• sterilise
• digestion (denatures proteins)
• helps with absorption of b12 and iron

Question 9

what is achlorhydria

Answer 9

absent or low gastric acid

can be a result of pernicious anaemia

Question 10

what kind of pump is in the parietal cells

Answer 10

H+/K+ ATPase proton pump

Question 11

how do the proton pumps in parietal cells work

Answer 11

• H+ is actively pumped out of cells and into the stomach
• in exchange K+ enters the cell
• HCO3- is formed in the cell and transported out into the bloodstream
• in exchange Cl- enters the cell
• HCl formed

Question 12

what reaction happens in the bloodstream with HCO3-

Answer 12

H2O + CO2 H+ + HCO3-

Question 13

why does Cl- enter the cel after HCO3- moves out

Answer 13

to keep the pH and osmolarity in equilibrium

Question 14

what happens when the parietal cell secretes HCl

Answer 14

the tubulovesicles fuse with canaliculus

increased SA and numbers of H+/K+ ATPase

increased acid secretion into gut lumen

Question 15

what are the protection of the gastric mucosa from acid

Answer 15

mucus layer

bicarbonate secretion

Question 16

autocrine

Answer 16

molecule that targets itself

Question 17

paracrine

Answer 17

targets adjacent cells

Question 18

endocrine

Answer 18

released into circulation to target distant cells

Question 19

where are ecl cells located and what do they secrete

Answer 19

located in body of stomach

secrete histamine

Question 20

what does histamine do

Answer 20

paracrine

stimulates acid secretion from adjacent parietal cells

Question 21

what releases Ach

Answer 21

vagus nerve and enteric neurons

Question 22

what does Ach stimulate

Answer 22

1. parietal cells to stimulate HCl
2. ECL cells to release histamine–> stimulates parietal
3. G cells to release gastrin –> stimulates parietal and ECL

Question 23

where are D cells located

Answer 23

in the antrum of the stomach

Question 24

what do D cells do

Answer 24

secrete somatostatin which is paracrine and endocrine

- inhibit acid secretion by acting on adjacent G cells and inhibiting gastrin release

Question 25

what do G cells do

Answer 25

secrete gastrin which is an endocrine hormone stimuates acid secretion indirectly via ECL cells goes into circulation and binds to ECL cells which secrete histamine which stimulates parietal cells to release HCl

Question 26

where are G cells located

Answer 26

in the antrum of thes tomach

Question 27

what is the cepahlic phase

Answer 27

initiated by the thought, sight , smell of food mediated by the vagus nerve through neurotransmitter Ach which directly stimulates the parietal cell to release HCl

Question 28

what is the gastric phase

Answer 28

distension of both the body and the antrum causes acid secretion mediated by the vagus nerve protein in the antrum (mainly breakdown products eg aas) stimulates G cells to secrete gastrin

Question 29

what is the intestinal phas

Answer 29

inhibition of acid secretion - HCl in antrum causes D cells to release somatostatin which inhibits V cells from releasing gastrin Also HCl in duodenum stimulates S cells to release secretin which inihibits gastric acid and gastric emptying and stimulates pancreatic HCO3- secretion to neuralise acid Partially digested fats and proteins in the duodenum stimulate CCK which inhibits gastric acid and gastric emptying

Question 30

what are the 2 functions of CCK

Answer 30

- partially digested fats and proteins in the duodenum stimulate CCK which inhibits gastric acid and gastric empting - stimulates release of pancreatic enzymes and gall bladder contraction to release bile