Lecture 8- Flashcards Preview

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Flashcards in Lecture 8- Deck (30):
1

contents of saliva

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

2

major roles of the stomach

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

3

Gastric motility

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

4

what is required for normal gastric emptying

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

(positive feedback from duodenum)

5

what causes delayed gastric emptying

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

6

what causes rapid gastric emptying

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

7

what are the 4 types of cells in the stomach

parietal cells
ECL cell
G cell
D cell

8

what is the role of gastric acid in the stomach

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

9

what is achlorhydria

absent or low gastric acid

can be a result of pernicious anaemia

10

what kind of pump is in the parietal cells

H+/K+ ATPase proton pump

11

how do the proton pumps in parietal cells work

- 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

12

what reaction happens in the bloodstream with HCO3-

H2O + CO2 H+ + HCO3-

13

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

to keep the pH and osmolarity in equilibrium

14

what happens when the parietal cell secretes HCl

the tubulovesicles fuse with canaliculus

increased SA and numbers of H+/K+ ATPase

increased acid secretion into gut lumen

15

what are the protection of the gastric mucosa from acid

mucus layer
bicarbonate secretion

16

autocrine

molecule that targets itself

17

paracrine

targets adjacent cells

18

endocrine

released into circulation to target distant cells

19

where are ecl cells located and what do they secrete

located in body of stomach
secrete histamine

20

what does histamine do

paracrine
stimulates acid secretion from adjacent parietal cells

21

what releases Ach

vagus nerve and enteric neurons

22

what does Ach stimulate

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

23

where are D cells located

in the antrum of the stomach

24

what do D cells do

secrete somatostatin which is paracrine and endocrine
- inhibit acid secretion by acting on adjacent G cells and inhibiting gastrin release

25

what do G cells do

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

26

where are G cells located

in the antrum of thes tomach

27

what is the cepahlic phase

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

28

what is the gastric phase

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

29

what is the intestinal phas

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

30

what are the 2 functions of CCK

- 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