7 Functions of the Stomach

Question 1

What are the 2 families of hormones that have roles in the GI tract?

Answer 1

• Gastrin family
• Secretin family

Question 2

What structural component of the stomach gives it its ability to distend?

Answer 2

Rugae (temporary folds) in the mucosa of the stomach

Question 3

How many layers of muscle does the stomach have?

Answer 3

3 layers

Question 4

What does the stomach do to help with protein digestion? (2)

Answer 4

1. Unravel proteins- larger surface area
2. Activates proteases

Question 5

Name the cells that are responsible for acid production in the stomach. What are they stimulated by?

Answer 5

Parietal cells

Stimulated by gastrin, histamine, Ach (acting through CCK, H2, Mcr receptors on parietal cell)

Question 6

What 2 factors will increase acid production from parietal cells?

Answer 6

• Amino acids/peptides detected in stomach lumen
• When stomach= distended

Question 7

What 2 factors cause a reduction in stomach acid production?

Answer 7

• When stomach distension reduces
• Low pH detected in stomach

Question 8

What are the 3 phases of digestion?

Answer 8

1. Cephalic
2. Gastric
3. Intestinal

Question 9

In simple terms, how does the stomach defend itself from its acidic environment?

Answer 9

Produces thick layer of alkaline mucus

Question 10

What roles do the enteroendocrine and enterochromaffin cells have in the gut?

Answer 10

Enteroendocrine

• Secrete hormones
• (genrally identified by letters G, S, D)

Enterochromaffin

• Secrete histamine

Question 11

What veins drain the liver?

Answer 11

Hepatic veins drains liver

Portal vein DOESN’T drain liver

Question 12

Give an example of neurocrine control of the stomach .

Answer 12

Gastrin releasing peptide

GRP released from post ganglionic fibres of vagus nerve

Increases release of Gastrin from G cells

Question 13

Two hormones in the gastrin family are Gastrin and CCK (cholecystokinin). Where are these hormones released from and what are their functions?

Answer 13

• Gastrin
  
  • Released: G cells in antrum of stomach
    
    • Increases gastric acid secretion
• CCK (Cholecytokinin)
  
  • Released: I cells in duodenum and jejunum
    
    • Increases pancreatic and gallbladder secretions
      
      • Stimulated by fat and protein
      • Gall bladdder contracts
      • Pancreas stimulated

(Gastrin and CCK very similar- some of the receptors are interchangeable)

Question 14

Two hormones in the secretin family and Secretin and Gastric Inhibitory Polypeptide. Where are each of these hormones secreted from and what are their functions?

Answer 14

• Secretin
  
  • S cells in duodenum
  • Stimulated by H⁺ and fatty acids
    
    • Increase HCO₃ from pancreas/gallbladder
    • Decreases gastric acid secretion
• Gastric Inhibitory Polypeptide
  
  • Cells in duodenum and jejenum
  • Stimulated by sugars, amino acids and fatty acids
    
    • Increase insulin
    • Decreased gastric acid secretion

Question 15

Locate the stomach on this image.

Answer 15

Question 16

Fill in the missing labels:

Answer 16

Question 17

Describe the transition of epithelial cell types from the lower oesophagus to the stomach.

Answer 17

Abrupt transition

Stratified squamous–> columnar

Question 18

Fill in the missing gaps 1-5:

Answer 18

Question 19

Fill in the missing labels:

Answer 19

Question 20

Different cell types are distributed differently in the stomach. What substances are primarily secreted in the:

Cardia

Fundus/body

Pylorus

Answer 20

Question 21

Fill in the missing labels on the coeliac trunk: 1-11

(Watch video again: https://youtu.be/5ZWooxbJCEg)

Answer 21

Question 22

If a patient has an ulcer in the first part of the duodenum which artery could it perforate into? What will happen to the patient?

Answer 22

Gastroduodenal artery

Patient will vomit up blood/ have blood in peritoneal cavity

Question 23

Name the vein that drains evrything from the gut

Answer 23

Portal vein

Question 24

Relaxation of the stomach is vagally mediated and the rugae facilitate the distension of the stomach. Why is the stomachs ability to relax so important?

Answer 24

We consume food faster than we can digest it

• Need to store food
• Allow food to enter stomach without raising intra-gastric pressure
• Prevent reflux of stomach contents

Question 25

Stomach acid unravels ingested proteins and also activates proteases eg. pepsinogen to pepsin. Why is this necessary?

Answer 25

Unravel proteins to help with digestion So we don't break our own cells down

Question 26

Name 3 substances/molecules that stimulate parietal (oxyntic) cells (to release HCl).

Answer 26

1. Gastrin 2. Histamine 3. Ach

Question 27

There are 3 'ON' buttons that cause parietal (oxyntic) cells to release HCl. How do eahc of these work? (Ach, Histamine, Gastrin)

Answer 27

1. **_Gastrin_** 1. Stimulate CCK (cholecystokinin) receptors on parietal cell 2. Acid released 2. **_Histamine_** (like **amplifier**) 1. Modulates input from gastrin 3. **_Ach_** 1. Vagus nerve stimulates muscarinic receptor using ACh

Question 28

Where is gastrin secreted from and how is it controlled?

Answer 28

Secreted from: * **G cells** in **antrum** of stomach Stimulated by: * **Peptides** and **amino acids** in stomach lumen * Vagal stimulation * Acetylcholine * Gastrin releasing peptide

Question 29

At a molecular level- describe how the parietal cell produces acid.

Answer 29

* **H⁺/K⁺ ATPase** * Pumps hydrogen out into stomach lumen * Water split inside cell Venous blood leaving blood made slightly more alkaline- bicarbonate used later on in GI tract

Question 30

Need to be able to explain stomach secretions. Use these diagrams- talk it through.

Answer 30

Question 31

What are the 3 phases of digestion and what happens during each phase?

Answer 31

1. Cephalic (30% HCl Production) 1. Parasympathetic stimuli 1. Vagus nerve stimulates parietal cells and G cells (before food swallowed- anticipating food) 2. Increased gastric motility 2. Gastric (60% HCl production) 1. Food distends stomach 1. - stimulates Vagus 1. Stimulates parietal cells and G cells 2. Amino acids and peptides stimulate G cells 3. Food acts as buffer- removes inhibition on gastrin secretion 4. Enteric nervous system causes strong smooth muscle contractions 3. Intestinal (10% HCl production)​ 1. ​Chyme initally stimulates gastrin secretion 2. THEN inhibition of G cells 1. enterogastric reflex-activated by presence of lipids 1. reduce vagal stimulation

Question 32

How does the stomach protect itself from its own secretions?

Answer 32

Question 33

What is the effect of NSAIDs on prostaglandin release?

Answer 33

Decrease prostaglandin release

Question 34

Give examples of sunstances that can breach the stomach defences

Answer 34

Question 35

Which arteries supply the greater and lesser curves of the stomach?

Answer 35

* Lesser curve * Left and right gastric arteries * Greater curve * Left and right gastroepiploic arteries