7) Functions of the Stomach Flashcards Preview

Gastrointestinal Tract > 7) Functions of the Stomach > Flashcards

Flashcards in 7) Functions of the Stomach Deck (35):
1

What are the basic functions of the stomach (4)?

Stores food
Disrupts food (contractions)
Continues digestion
Disinfects food

2

What is the first section of the stomach called?

Cardia, where oesophagus enters

3

What are the other sections of the stomach (top to bottom)?

Fundus, body, antrum, pylorus (+sphincter)

4

What is the change in epithelium at the cardia?

Transition of stratified squamous to columnar (secretion)

5

Describe the muscosa of the stomach:

In folds (rugae), to allow distension by flattening of these folds

6

What are gastric pits?

'Little holes' on stomach surface
These pits have gastric glands (specialised cells) at the bottom

7

What causes the movement of substances from the cardia to pylorus?

Upper stomach has basal tones created by sustained contractions which force flow down funnel shaped stomach

8

How many muscle layers does the stomach have?

3 - oblique, circular and outer longitudinal

9

What is receptive relaxation?

As food travels down oesophagus, vagus nerve triggers relaxation of orad stomach wall (flattening of rugae)

10

What does receptive relaxation stop?

Stops rises in intra-gastric pressure
Prevents reflux

11

What are the functions of stomach acid?

Helps unravel proteins - larger SA
Activates proteases - pepsin
Disinfection

12

What do parietal cells secrete?

HCl
Intrinsic factor

13

What do G cells secrete?

Gastrin

14

What do enterochromaffin like cells secrete?

Histamine

15

What do chief cells secrete?

Pepsinogen

16

What do D cells secrete?

Somatostatin

17

What do mucous cells (surface + neck) secret?

Mucus

18

What are the predominant secretions of the cardia?

Mucus

19

What are the main secretions of the fundus and body?

Mucus, HCl, pepsinogen

20

What are the main secretions of the pylorus?

Gastrin, somatostatin

21

What stimulates secretion of stomach acid?

Gastrin, histamine and ACh

22

What feature of the parietal cell allows increased acid secretion?

Invaginations on cell surface (canaliculi) increase SA for secretion

23

What stimulates gastrin secretion?

Peptides/AAs in the stomach lumen
Vagus stimulation - ACh, gastrin releasing peptide

24

What inhibits acid production?

Low stomach pH - food acts as buffer
Low pH also activates D cells --> somatostatin which inhibits G and ECL cells
Reduction in stomach distension reduces vagal activity

25

Describe the formation of HCl:

Water split to OH- and H+
H+ and Cl- into stomach lumen to form HCl
Uses H+/K+ ATPase

26

What happens to the OH- produced in HCl formation?

Combines with CO2 to form HCO3-
This moves into bloodstream, alkaline tide (HCO3-/Cl- antiporter)

27

What are the 3 phases of digestion?

Cephalic
Gastric
Intestinal

28

What occurs in the cephalic phase of digestion?

Vagus nerve stimulates parietal and G cells in response to smelling, tasting, chewing and swallowing
Increase in gastric motility
30% of HCl

29

What occurs in the gastric phase of digestion?

Distension of stomach stimulates vagus (parietal and G cells)
Presence of AA/peptides stimulates G cells
Food acts as buffer so no inhibition of gastrin
Enteric NS and gastrin cause strong SM contractions

30

What occurs in the intestinal phase of digestion?

Inhibition of G cells due to presence of lipids - enterogastric reflex, reduced vagal
Chyme stimulates CCK and secretin

31

What defences does stomach have against acid?

Mucus and HCO3- - form thick alkaline viscous layer over epithelium
High turnover of epithelial cells
Prostaglandins maintain mucosal blood flow

32

What can breach stomach defences?

Alcohol - dissolves mucus layer
Helicobacter pylori - inflamm of stomach lining
NSAIDS - inhibit prostaglandins

33

What can breach of stomach defence lead to?

Gastritis
Ulceration
Reflux disease

34

What pharmacological interventions can be used to reduce acid secretion?

H2 blockers - cimetidine
Proton pump inhibitors - omeprazole

35

What slows gastric emptying?

Fat, low pH and hypertonicity in duodenum