Physiology

Question 1

What is the LES?

Answer 1

It is just the diaphragm!

Question 2

What are the muscles in the oesophagus and why is it relevant?

Answer 2

Top third is skeletal and is under our control
Middle third is skeletal and smooth so not so under our control
Lowest third is smooth muscle so we have no control over it

Question 3

How much can a stomach store?

Answer 3

Up to 4L of food/fluid

Question 4

What are the three steps that the stomach is responsible for?

Answer 4

Churns the bolus

Mixes it with enzymes to become chyme

Stores the chyme

Question 5

What are the three types of cells involved in secretion? What do they secrete? Where in the pit are they?

Answer 5

Parietal cells - HCl - part way down into the stomach pits

Chief cells - pepsinogen - bottom of the pit

Mucus (foveolar) cells - mucus - at the top of the stomach pits

ECL cell - histamine - lower end

Question 6

How is pepsin made?

Answer 6

Pepsinogen is activated by HCl

Question 7

What does pepsin do?

Answer 7

A protease that breaks down protein

Question 8

What is the role of mucin?

Answer 8

It is protective and ensures HCl and pepsin don’t breakdown the stomach wall

Question 9

What does HCl do?

Answer 9

Activate pepsinogen

Question 10

What does the mucus of the stomach contain?

Answer 10

Mucin

Gastric surfactant

Question 11

What does the mucus protect the mucosal cells from?

Answer 11

H+

HCl

Question 12

What stimulates the ECL?

Answer 12

PNS - ACh

Question 13

What does the histamine do?

Answer 13

Stimulates parietal cells to stimulate acid secretion

Question 14

What do parietal cells respond to?

Answer 14

ACh (PNS)
Histamine (ECL cell)
Gastrin (G cells)

Question 15

Which pump is used by parietal cells to secrete HCL?

Answer 15

Proton pump

Question 16

What type of epithelium lines the stomach?

Answer 16

Cardiac mucosa - cardiac

Columnar epithelium - body

Question 17

What stimulates Chief Cells?

Answer 17

ACh

Question 18

What are the cells that are specialised in the antrum?

Answer 18

D cells

G cells

Question 19

What is the G cell stimulated by?

Answer 19

Presence of amino acids

Question 20

What does G stand for in the G cell?

Answer 20

Gastrin

Question 21

What does gastrin do?

Answer 21

Stimulates parietal cells and acid secretion so that the HCL can be released to activate pepsin which can then breakdown the amino acids

Question 22

What is the delta cell stimulated by?

Answer 22

Acid (low pH)

Question 23

What does the delta cell do?

Answer 23

Releases somatostatin

Question 24

What does somatostatin do?

Answer 24

Suppresses the PNS so fewer things stimulate the parietal and ECL cells

Question 25

Which cells secrete/inhibit acid secretion?

Answer 25

Promotes:
Mainly G cells

ECL
Parietal cell
Chief cell

Inhibits:
D cell

Question 26

What are the protective mechanisms of the stomach?

Answer 26

Regulation of acid production
Mucosal barrier
Epithelial repair

Question 27

What is the post prandial pH of the stomach?

Answer 27

Post prandial pH 1-2

Question 28

How are the columnar epithelial cells specialised?

Answer 28

The apical surface of the columnar cells are resistant to low pH, but the lateral and basal surfaces are not

Question 29

How could acid damage a columnar cell?

Answer 29

If one dies, access to lateral surface then arises

Question 30

What contributes to the mucosal barrier?

Answer 30

Apical membrane resistance
Gastric surfactant
Mucin

Question 31

How can alcohol affect the stomach mucosal barrier?

Answer 31

Dissolves the gastric surfactant

Question 32

How quickly does the epithelium repair itself?

Answer 32

Roughly 1 hr

Question 33

What happens in acute repair of the epithelium?

Answer 33

You get vasodilation and more flow of immune cells.
A mucoid cap is then formed (thick mucin layer).
The younger epithelial cells then migrate up from the gastric pits.