Stomach: histology and physiology

Question 1

What forms pits and glands in the histology of the stomach?

Answer 1

Mucous secreting surface cells

These cells dip down to form pits which continue down as glands.

Question 2

What do Chief (Zymogen) cells secrete?

Answer 2

Pepsinogen

HCl activates pepsinogen to pepsin.

Question 3

What do Parietal (oxyntic) cells secrete?

Answer 3

HCl & Intrinsic factor

Question 4

Where are Parietal (oxyntic) cells not located?

Answer 4

Cardia or prepyloric antrum

Question 5

What type of cells secrete gastrin in the pylorus?

Answer 5

G cells

Question 6

What do D cells secrete?

Answer 6

Somatostatin

Question 7

What do Chromaffin (ECL) cells in the pylorus and body secrete?

Answer 7

Histamine, serotonin, and endorphin

Question 8

Fill in the blank: The pylorus contains _______ cells that secrete gastrin.

Answer 8

G cells

Question 9

True or False: Chief (Zymogen) cells are found in the cardia of the stomach.

Answer 9

False

Question 10

What activates pepsinogen secreted by Chief (Zymogen) cells?

Answer 10

HCl

Question 11

What are the three phases of gastric secretion?

Answer 11

Cephalic phase, Gastric phase, Intestinal phase

Question 12

What mediates secretion during the cephalic phase?

Answer 12

Vagal input

This phase is triggered by the sight of food.

Question 13

What substances are released during the cephalic phase?

Answer 13

Gastrin Releasing Peptide (GRP), Acetylcholine

These substances initiate the secretory function.

Question 14

What triggers the gastric phase of gastric secretion?

Answer 14

Meal constituents, physical distension of stomach

Oligopeptides especially stimulate gastrin secretion.

Question 15

How does the buffering effect of a meal influence gastric secretion?

Answer 15

Reduces gastric acidity

This reduction prevents the usual shut-off of secretion via somatostatin.

Question 16

What triggers somatostatin secretion in the intestinal phase?

Answer 16

Once the meal has left the stomach

Somatostatin turns off G and ECL cells.

Question 17

What are the agonists of parietal cells?

Answer 17

Gastrin, Histamine, Acetylcholine

These substances stimulate acid production.

Question 18

Which substances promote acid production from parietal cells?

Answer 18

Gastrin, Histamine, Acetylcholine

Acetylcholine acts on M3 muscarinic receptors.

Question 19

Which substances inhibit acid production from parietal cells?

Answer 19

Somatostatin, Low pH

These factors help regulate acid levels.

Question 20

What initiates the production of hydrogen ions in parietal cells?

Answer 20

Water & carbon dioxide

This reaction is stimulated by carbonic anhydrase.

Question 21

What is the role of H+/K+-ATPase in acid production?

Answer 21

Exchanges hydrogen ions for potassium ions

This process is crucial for maintaining gastric acidity.

Question 22

What triggers the fusion of vesicles with the cell membrane in parietal cells?

Answer 22

Histamine, Acetylcholine, Gastrin stimulation

This process leads to increased intracellular calcium.

Question 23

How is chloride secretion achieved in parietal cells?

Answer 23

Through chloride channels

K+ channels allow for electroneutral chloride release.

Question 24

What is the mechanism of action of Omeprazole

Answer 24

inhibits proton pump irreversibly– lasts 18 hours

Leads to hyperplasia of G/ ECF cells, hypergastrinaemia (possibly increased risk of gastric carcinoid)

Question 25

Name two H2 receptor antagonists, state the half life, and mechanism of action.

Answer 25

Cimetidine, ranitidine competitive antagonist – half-life 1.5 hours

Question 26

What is the composition of the secreted substance by cell surface mucus cells at the gastric mucosal surface?

Answer 26

Mucus + bicarbonate ## Footnote This composition provides a protective barrier at the gastric mucosa.

Question 27

What mechanical function does mucus and bicarbonate serve at the gastric mucosal surface?

Answer 27

Creates an ‘unstirred’ water layer and impedes ion transfer from lumen to epithelium ## Footnote This helps protect the mucosa from injury.

Question 28

What is the pH range maintained at the mucosal border compared to the luminal pH?

Answer 28

5-7 at mucosal border vs 1-2 in lumen

Question 29

What stimulates the production of mucus and bicarbonate?

Answer 29

Vagal stimulation and prostaglandins

Question 30

What substances inhibit mucus and bicarbonate production?

Answer 30

NSAIDs and anticholinergic drugs ## Footnote This inhibition is a reason why NSAIDs can cause ulcers.

Question 31

What effect does H. pylori have on mucus production?

Answer 31

Increases the rate of breakdown of mucus by proteases and lipases

Question 32

What is the daily production range of gastric juice?

Answer 32

500-2500mL/day

Question 33

What is the term for the relaxation of the fundus and upper stomach when food enters?

Answer 33

Receptive relaxation

Question 34

What triggers receptive relaxation in the stomach?

Answer 34

Vagal mediation triggered by movement of pharynx and esophagus

Question 35

What controls peristaltic waves in the stomach?

Answer 35

Basal electrical rhythm

Question 36

What happens during the contraction of the antrum, pylorus, and duodenum?

Answer 36

Solid masses are crushed against pylorus and churned

Question 37

What factors influence gastric emptying time?

Answer 37

Type of food ## Footnote Carbohydrates leave quickly, proteins more slowly, and fatty foods the slowest.

Question 38

What initiates the process of vomiting?

Answer 38

Salivation and sensation of nausea

Question 39

What process empties the stomach to vomit?

Answer 39

Reverse peristalsis

Question 40

What happens to the glottis during vomiting?

Answer 40

Closes and breath is held in mid-inspiration

Question 41

What role do abdominal muscles play during vomiting?

Answer 41

Contract to raise intra-abdominal pressure

Question 42

What happens to the lower oesophageal sphincter during vomiting?

Answer 42

Relaxes to allow gastric contents to be ejected

Question 43

What signals can trigger vomiting?

Answer 43

Irritation of upper GI mucosa, central causes, serotonin (5-HT), and dopamine (D2) involvement

Question 44

True or False: The vestibular nuclei are involved in vomiting due to motion sickness.

Answer 44

True

Question 45

Fill in the blank: Serotonin (5-HT) and _______ receptors are involved in nausea and vomiting.

Answer 45

dopamine (D2)

Question 46

What is GORD and when is it commonly seen?

Answer 46

GORD (Gastro-Oesophageal Reflux Disease) is especially seen after vagotomy ## Footnote GORD may also be associated with bile reflux

Question 47

What complication is characterized by difficulty swallowing after gastrectomy?

Answer 47

Dysphagia ## Footnote Dysphagia can occur post-gastrectomy

Question 48

What condition involves delayed gastric emptying following gastrectomy?

Answer 48

Chronic gastroparesis ## Footnote Treatment may include prokinetics like metoclopramide

Question 49

What surgical procedure may be required for chronic gastroparesis?

Answer 49

Completion gastrectomy & Roux-en-Y formation ## Footnote This may be necessary in severe cases

Question 50

What is bezoar formation and how is it related to post-gastrectomy?

Answer 50

Bezoar formation can occur partly due to achlorydia ## Footnote It may lead to further complications

Question 51

What is a common outlet obstruction symptom after gastrectomy?

Answer 51

Stomatitis / Recurrent ulcers – marginal / anastomotic ## Footnote These may lead to complications requiring treatment

Question 52

What are the symptoms of bilious vomiting and alkaline gastritis?

Answer 52

Bilious vomiting & alkaline gastritis can occur due to bile reflux ## Footnote May require treatment with prokinetics

Question 53

What is stump carcinoma?

Answer 53

Stump carcinoma is a potential complication after gastrectomy ## Footnote It refers to cancer developing in the remaining stomach tissue

Question 54

What is afferent loop syndrome and its symptoms after gastrectomy?

Answer 54

Afferent loop syndrome involves pain, bloating, nausea, and vomiting (not bilious) 20-60 minutes after a meal ## Footnote It may also cause diarrhea and steatorrhea due to bacterial overgrowth

Question 55

What effect does post-gastrectomy have on storage capacity and weight?

Answer 55

↓ storage capacity leads to early satiety and weight loss ## Footnote This is due to the restrictive effect of the surgery