Oesophagus and Stomach

Question 1

What are the layers in the oesophagus? (4)

Answer 1

Mucosae
Submucosae
Muscularis
Serosal Adventitia

Question 2

What is the mucosae layer made up of?

Answer 2

Epithelium
Lamina propria (loose connective tissue that connects the other two layers together)
Muscularis Mucosae

Question 3

What does the submucosae contain?

Answer 3

Connective tissue containing nerve plexus and glands

Question 4

Where does the oesophagus start and end?

Answer 4

Start at C5 and end at T10

Question 5

How is oesophagus designed for it’s function?

Answer 5

It’s function is to deliver food
It has to be robust and handle extreme temperatures and textures by being stratified non keratinising squamous epithelia.

Question 6

What is the upper oesophageal sphincter made from?

Answer 6

Skeletal muscle

Question 7

What is the lower oesophageal sphincter made from?

Answer 7

Skeletal and smooth muscle

Question 8

What is the function of the gastro-oesophageal junction?

Answer 8

acid reflux is prevented by the diaphragm and has an epithelial transition

Question 9

What is the point of the gastric folds in the stomach?

Answer 9

The folds stretchh when the stomach fills it allows the stomach to get bigger. When the stomach is full the folds are gone and the stomach wall is smooth

Question 10

Give an example of when the diaphragm fails to prevent acid reflux?

Answer 10

Pregnancy when foetus pushes stomach upwards

Question 11

5 sections of the stomach and what do they make?

Answer 11

Cardia and Pyloric only make mucus
Body and Fundus makes mucus, HCl and pepsinogen
Antrum makes gastrin

Question 12

What are the functions of stomach?

Answer 12

• break down food into smaller particles stored due to aid and pepsin
• hold food and release at a controlled steady state into duodenum
• kill parasites and certain bacteria

Question 13

What do cardiac and pylori sections make?

Answer 13

Mucus secreting with lots of bicarbonate that neutralises the stomach acid as it is trapped in mucus gel. This means epithelial surface of pH 6-7 but the lumen pH 1-2. Bicarbonate prevents acid damaging the cells.

Question 14

In the body and fundus, what is made?

Answer 14

• Make acid that denatures large proteins
• Pepsinogen producing which is precursor to pepsin which breaks down protein
• mucus producing but with no bicarbonate

Question 15

What does peristalsis do in stomach?

Answer 15

Propels chyme towards colon and driven by ANS by vagus nerve. It makes up 20% of contractions

Question 16

What does segmentation do in stomach?

Answer 16

It is more common but weaker, it mixes everything up and moves fluid chyme towards pyloric sphincter and solid chyme move back up. It is less coordinated than peristalsis. It is controlled by a local system- enteric nervous system.

Question 17

What do gastric chief cells do?

Answer 17

Secretes pepsinogen

Question 18

What do gastric chief cells have that make them good at their job?

Answer 18

have lots of RER for making proteins
have lots of golgi for packaging and exporting
lots of apical secretion granules for SECRETE

Question 19

What do parietal cells do?

Answer 19

secrete acid

Question 20

What do parietal cells have that make them good at their job

Answer 20

Lots of mitochondria for lots of ATP
cytoplasmic tublulovesicles contain H+/K+ ATPase
internal caniculi extend to apical surface

Question 21

What happens to parietal cells when they are activated?

Answer 21

the tubulovesicles fuse with membrane and microvilli, and project into canaliculi and project into lumen of stomach

Question 22

what enzyme makes H+ and HCO3-?

Answer 22

Carbonic anhydrase

Question 23

What kind of environment does pepsinogen need to break down into pepsin?

Answer 23

Acidic

Question 24

What happens in pyloric antrium?

Answer 24

local peptide hormone - gastrin stimulate histamine release from chromaffin cells that stimulate acid production

Question 25

What are the phases of gastric selection?

Answer 25

1. cephalic
2. gastric
3. intestinal

Question 26

What happens in the cephalic phase?

Answer 26

Before food enters the body, it prepares for the food bolus by increasing acid and pepsinogen production. It is a conditioned response to sensory stimuli via the vagus nerve

Question 27

What happens in the gastric phase?

Answer 27

A powerful local response to local stimuli activating tissue in response via chemo and stretch receptors. The chemoreceptors activate muscles and glands releasing acid, pepsin etc to facilitate digestion. Stomach distention is a central nervous response via the vagus nerve

Question 28

What happens in the intestinal phase?

Answer 28

The food that is left in the stomach goes into the intestine as chyme and intestines respond to the chemical constituents of chyme and the pH. Signals sent to brain leading to inhibitory (so enterogastric reflux) or excitatory effect (so stomach works harder)

Question 29

When does an excitatory response happen in the intestinal phase?

Answer 29

When the chyme has a high protein content so the body alerts the stomach it’s not fully breaking down the food and needs to work harder

Question 30

What hormones have an inhibitory effect on the intestinal phase?

Answer 30

gastric inhibiting peptide
cholecystokinin
secretin

Question 31

What does omeprazole do?

Answer 31

inhibit histamine binding to receptors on parietal cells

Question 32

What does ranitidine do?

Answer 32

H+/K+ATPase pump inhibitor