Upper GIT Physiology and disorders

Question 1

Exocrine cells

Answer 1

Mucous cells – secrete mucus

• Important because it sits at the top of internal muscuso and acts as a cell layer to prevent burning of ACID
• seen as the protective cells

• Chief cells – secrete pepsinogen & gastric lipase
- is in active form

• Parietal cells – secrete HCl & intrinsic factor (glycoprotein for B12 absorption)
- B12 is absorbed at the end of small intenstine

Question 2

Endocrine/ Paracrine cells

Answer 2

• Enterochromaffin-like (ECL) cells
• G cells
• D cells

other cells
Stem cells filled in Stomach and small intestine

Question 3

Roles of HCl

Answer 3

• Activates pepsinogen (zymogen) -
converts it in active pepsin
• Contributes to nonspecific disease resistance by destroying most ingested pathogens

Question 4

Mucus is a protective barrier

Answer 4

1. Impermeable mucosal cells: luminal membranes are impermeable to H+
2. Tight junctions: prevent HCl from penetrating
3. Mucous coat: physical barrier to HCl
4. Chemical barrier: HCO3- neutralizes HCl

Question 5

Regulation of gastric secretion

- neural control

Answer 5

Acetylcholine (ACh) – released by intrinsic nerve plexuses within the stomach, under the control of short local reflexes and vagal stimulation

Question 6

Regulation of gastric secretion

- hormonal control

Answer 6

• Enterochromaffin-like (ECL) cells – secrete histamine among the parietal and chief cells (oxyntic mucosa)
• G cells – secrete gastrin into the bloodstream
- Food reaches mouth > g cells release gastin > stimulates
ECL and D cells > Histamine

• D cells – secrete somatostatin in response to acid

Question 7

Shut down system

Answer 7

d cells sense change in pH and produce somatostatin

And has opposite affect and shuts down system

Question 8

Control of gastric secretion involves three phases:

Answer 8

1. cephalic phase -factors arising before food reaches the stomach (thinking of food - long reflex)
2. gastric phase -factors resulting from food in the stomach (food is present)
3. intestinal phase -factors in the duodenum after food has left the stomach

Question 9

1. Cephalic phase

Answer 9

– sight and thought of food increase gastric juices.

Question 10

2. Gastric phase

Answer 10

– begins when food is in the stomach (especially proteins).

Question 11

3. Intestinal phase

Answer 11

factor that originates in the small intestine (duodenum). Inhibitory phase, which helps with stomach emptying.

Question 12

Gastritis

Answer 12

Breakdown of the mucus barrier can result in inflammation. >
Chemical breakdown of mucosal barrier: alcohol, aspirin and non steroidal
anti-inflammatory drugs (NSAIDs such as ibuprofen) > GASTRITIS
Redness (erythema) is caused by excessive production of HCl and gastric juices when no need it

Question 13

Gastritis treatment

Answer 13

• antacids tablets: neutralize HCl
• lifestyle changes: avoid aggravating food (spicy food, coffee, chocolate, mint and
tomato).

Question 14

Peptic ulcers

Answer 14

Extreme gastritis or bacterial infection increase the chance of developing peptic ulcers.

Discovery of the acid-resistant bacteria Helicobacter pylori
• Flagella
• Prefer to settle in the
antrum (no parietal
cells)
• Production of urease
to buffer HCl

Question 15

Peptic ulcers trmt and diagnosis

Answer 15

Diagnosis: urea breath test (UBT), if positive endoscopy to check for ulcers
Treatment:
• antibiotics (2 weeks)
• proton pump inhibitors (action on H+-K+ ATPase pump)
• blocker for histamine receptor 2 (H2) (cimetidine): inhibits production of HCl, no effect on H1 receptors (involved in allergic respiration disorders)
• lifestyle changes

Question 16

Pernicious anemia

Answer 16

Autoimmune disease that affects the parietal cells. > Absence of intrinsic factors (glycoprotein) release by
parietal cells.
> Impossibility of the body to absorb enough vitamin
B12 in ileum
> Defective erythrocyte production
Treatment:
• Regular injections of vitamin B12