Anatomy of the Oesophagus and Stomach

Question 1

Where does the oesophagus run from?

Answer 1

C6-T10.

Question 2

What is the function of the levator pili palatini?

Answer 2

The levator pili palatini contracts to move the soft palate anteriorly and posteriorly to block the opening of the nasopharynx.

Question 3

What is the function of the musculus uvulae?

Answer 3

The musculus uvulae contracts to move the uvulae upwards to block opening to nasopharynx.

Question 4

What is the upper oesophageal sphincter formed of?

Answer 4

It is formed of skeletal voluntary muscle; Inferior pharyngeal muscle and the cricopharyngeal muscle. These contract to prevent reflux of food to the airways and prevent air entering oesophagus.

Question 5

What is the lower oesophageal sphincter formed of?

Answer 5

It is formed of smooth muscle which contracts and relaxes to generate a peristaltic force to propel food to the stomach.

Question 6

What is the layers of the oesophagus?

Answer 6

Mucosa: stratified squamous non-keratinising epithelia, basement membrane, lamina propria and glands

Submucosa: Loose Connective tissue with large blood vessels and glands

Muscularis Externa: upper is striated skeletal muscle, middle is striated smooth and lower is smooth muscle.

Adventitia: Connective tissue with smaller blood vessels, lymphatics and nerves.

Question 7

What are the layers of the stomach?

Answer 7

Mucosa: Simple columnar epithelia, basement membrane, lamina propria. It contains chief cells, mucosal cells, parietal cells and G cells.

Submucosa: Loose Connective tissue with large blood vessels and glands

Muscularis Externa: Oblique muscle, circular muscle and longitudinal muscle. This rhythmically contracts to generate churning effect to turn bolus into chyme.

Gastric Serosa: Mesothelium of simple squamous epithelia and loose connective tissue lining the stomach.

Question 8

What is the composition and function of the rugae?

Answer 8

Rugae is responsible for expansion of the stomach and increase in stomach SA and volume which aids nutrient absorption. It is formed of the mucosal and submucosal layers

Question 9

What is the composition and function of the rugae?

Answer 9

Rugae is responsible for expansion of the stomach and increase in stomach SA and volume which aids nutrient absorption. It is formed of the mucosal and submucosal layers

Question 10

What are the cells of the gastric mucosa?

Answer 10

Neck cells which produce mucous to protect the simple columnar epithelia via the gel phase.

Parietal/ Oxyntic cells are found mainly in the fundus and body with some near the pyloric sphincter. They release gastric acid for protein digestion and intrinsic factor for B12 absorption.

Zymogenic Chief cells are found mainly in the cardiac and fundus region. They produce pepsinogens which are cleaved in the acidic stomach environment to pepsin.

Enteroendocrine cells are hormone-producing cells in the stomach which release serotonin to decrease gastric acid secretion and releases histamine to increase gastric acid secretion.

Question 11

Where is gastric acid secreted from?

Answer 11

Parietal cells secrete gastric acid containing HCL which is transported by the gastric pits to the stomach lumen.

Question 12

How is gastric acid secreted?

Answer 12

Ca2+/ cAMP downstream signalling activates the H+/K+ protein pump exchanger channel for H+ exudation.

Question 13

How does Ca2+/cAMP downstream signalling occur?

Answer 13

Parietal cells have G protein coupled receptors.

Ca2+
-> G cells release gastrin which binds to the CCK2 receptor on parietal cells. Activation of phospholipase enzyme which releases Ca2+ stores
->Vagus nerve releases acetylcholine which binds to muscarinic 3 receptors on parietal cells for Ca2+ influx.

cAMP release.
-> G cells release gastrin which binds to enteroendocrine cells to release histamine. Histamine binds to H2 receptors on parietal cells.

Question 14

What is the enterogastric reflex?

Answer 14

Food entering the duodenum stimulates stretch receptors to reduce gastric emptying via inhibiting gastric acid secretion. Gastric Enteroendocrine cells release serotonin, Vasoactive Intestinal Peptide to cause vasodilation of stomach smooth muscle and Glucose dependent insulinotropic peptide to release insulin to inhibit gastric acid secretion.

Question 15

What are stomach ulcers?

Answer 15

Open sores in the stomach lining which can be bleeding and lead to decreased appetite. It can be caused by NSAIDS which irritate the stomach mucosa.

Question 16

What are the NSAIDs?

Answer 16

NSAIDs are nonsteroidal anti-inflammatory drugs used mainly for analgesia and apraxia. They inhibit the Cyclooxygenase (COX) enzyme which catalyses the conversion of arachidonic acid to the inflammatory mediator prostaglandin and thromboxane.

Question 17

Examples of NSAIDs?

Answer 17

There are 4 common NSAIDs:
Diclofenac, naproxen, aspirin and ibuprofen.

Question 18

What are the treatments for stomach ulcers?

Answer 18

Histamine receptor antagonists, anticholinergic drugs and proton pump inhibitors.

Question 19

How do proton pump inhibitors treat stomach ulcers?

Answer 19

Protein pump inhibitors in vivo are converted into sulphonamides which irreversibly block the H+/K+ ATPase protein pump for gastric acid production. It has a delayed onset so must be taken before a meal.

Question 20

What is the gastroesophageal reflex?

Answer 20

Gastric acid enters the oesophagus and causes irritation and damage to the lining. This is caused by weakening of the lower oesophageal sphincter and causes heartburn.

Question 21

How is the gastroesophageal reflex treated?

Answer 21

Antacids like gabiscon/Pepto-Bismol form a protective coating overlaying the stomach contents to prevent it re-entering and damaging the oesophagus.