GI Physiology lecture 2

Question 1

Name 2 drugs affected by the stomach (acid)

Answer 1

penicillin, erythromycin

Question 2

what properties do drugs need to be absorbed in the stomach?

Answer 2

• lipid soluble

- weakly acidic

Question 3

Describe what a gastric sleeve is

Answer 3

stomach cut and stapled, 70-80% excised

Question 4

describe a gastric band

Answer 4

reduces food intake at any one time

Question 5

describe a Roux en Y bypass

Answer 5

gastric bypass with small pouch. Gastric balloon. Similar to band but inflated in stomach

Question 6

Name 3 surgical obesity treatments

Answer 6

• gastric sleeve
• gastric band
• roux en y bypass

Question 7

why is mucous secreted in the stomach? (mucous layer)

Answer 7

alkaline neutralises HCl acid

Mucous presents pepsin penetrating to stomach epithelia

Question 8

Describe tight junctions in the stomach

Answer 8

Protein complexes keeping cells together. They restrict movement of acid/protease to underlying stomach epithelia

Question 9

How are the stomach cells adapted to their harsh environment?

Answer 9

There is a high cell turnover. Damaged cells are renewed every 2-3 days from the gastric pits.

Question 10

What happens if there is a breakdown of barrier layer? i.e. mucous layer in the stomach?

Answer 10

cells are exposed to HCl and protease, this leads to a gastric/duodenal ulcer
This can extend deep into GI wall, damaging blood vessels and haemoorhaging
Severe complete evasion through wall causes a perforated ulcer. This causes the escape of food secretions and bacteria into the peritoneal cavity.
This can lead to peritonitis, then severe shock and death

Question 11

What is a likely organism responsible for GIT infections?

Answer 11

Helicobacter pylori

It infects the gastric mucosa. This causes reduced barrier efficiency of the mucosa and leads to ulceration

Question 12

treatment of Helicobacter pylori

Answer 12

2 antibiotics + PPI
Dirithromycin + amoxicillin + omeprazole
OR
Clarithromycin + amoxicillin/metronidazole + omeprazole

Question 13

pH equation

Answer 13

pH = pKa + log([A-]/{HA])

Question 14

what is peristalsis

Answer 14

a wave of muscular contraction

Question 15

how does food travel down the GIT?

Describe the forces that make this happen

Answer 15

Food bolus/chyme goes through duodenum
Circular muscles contract, preventing backflow of chyme
Longitudinal muscles contract further along to move food along

Question 16

describe diarrhoea in terms of muscles

Answer 16

Peristalsis of longitudinal muscle

Excessive ion and fluid loss

Question 17

Anti-diarrhoea medicine and how it works

Answer 17

Loperamide
Acts on MP, targets um opioid receptors in the MP. Reduces muscle tone so controls (liquids) stay in the intestine longer, so more absorption of fluid
less diarrhoea

Question 18

Role of bile acids

Where are they stored?

Answer 18

Bile acids responsible for liquid emulsification which is important in absorbing lipids e.g. vitamins ADEK
Bile acids stored in the gall bladder

Question 19

One cause of atherosclerosis

Answer 19

high cholesterol

Question 20

How do statins work?

Answer 20

Statins block the enzyme HMG-CoA reductase, hence reducing cholesterol

Question 21

Layers of the colon from outside to in

Answer 21

Serosa
Longitudinal muscle
MP (Myenteric Plexus)
Circular muscle 
Epithelium
Lumen

Question 22

How are bile acids made?

Answer 22

Acetyl CoA→HMG CoA→Mevalonate→Cholesterol→Bile acids

Question 23

Where are bile acids made?

Answer 23

Liver

Question 24

How do bile acids travel out of the liver?

Answer 24

Bile acids go through the intestinal veins→then the superior mesenteric vein→then the hepatic portal vein and then the iluem

Question 25

Hormone that causes bile to leave gallbladder

Answer 25

Cholecystokinin (CKK)
causes gall bladder to contract
bile released

Question 26

Describe the path of bile travel from the liver to the duodenum
THEN
path of travel from liver to gall bladder

Answer 26

Liver→common hepatic duct→common bile duct→duodenum

Liver→common hepatic duct→cystic duct→gall bladder