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Semester 3- GI > 4.1 Function of the Stomach > Flashcards

4.1 Function of the Stomach Flashcards

1
Q

What is receptive relaxation?

A

Vagally mediated relaxation of the orad region (fundus and upper body) which allows food to enter the stomach without raising the intragastric pressure. It prevents food reflux when swallowing.

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2
Q

What is peristalsis?

A

Coordinated contractions of the stomach to mix the stomach contents

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3
Q

What is ejected from the stomach and how regularly?

A

Chyme is ejected in liquid form at 3 ‘squirts’ a minute

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4
Q

Why is the stomach acidic?

A

To unravel proteins
Kill bacteria
Activates proteases

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5
Q

What cell releases HCl?

A

Parietal cell

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6
Q

What molecules stimulate parietal cells?

A

Gastrin, histamine and acetylcholine

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7
Q

Where is gastrin secreted from?

A

G cells

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8
Q

Where are G cells located?

A

The antrum of the stomach

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9
Q

What are G cells stimulated by?

A 
Peptides in the stomach (Gastrin-releasing peptide (GRP))
Vagal stimulation (acetylcholine)
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10
Q

Where is histamine released from?

A

Enterochromaffin-like cell (ECL)

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11
Q

What cell releases pepsinogens?

A

Chief cells

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12
Q

What cells release somatostatin?

A

D cells

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13
Q

What molecule inhibits gastrin?

A

Somatostatin

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14
Q

What stimulates somatostatin to be released?

A

Low pH

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15
Q

How is HCl made in the gut?

A

Water is split into its ions

The H+ combines with Cl- in the stomach lumen. Cl- is moved out of parietal cells by swapping with HCO3-

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16
Q

What happens to OH- after water has split in the gut?

A

Combines with CO2 to become HCO3-

This is moved into the blood stream as the alkaline tide

17
Q

Name the three stages of digestion and the proportion of time spent in each stage

A

Cephalic (30%)
Gastric (60%)
Intestinal (10%)

18
Q

What is meant by the ‘cephalic’ stage of digestion?

A

Smelling, chewing, tasting, swallowing with direct parietal cell stimulation by the vagus nerve. G cells are also stimulated and GRP is released.

19
Q

What is meant by the ‘gastric’ stage of digestion?

A

Distention of the stomach stimulates the vagus nerve to stimulate parietal and G cells. Amino acids and peptides also stimulate G cells. Food acts as a buffer in the stomach

20
Q

What is meant by the ‘intestinal’ stage of digestion?

A

G cells are inhibited by somatoctatin

21
Q

How does mucous work to protect the stomach?

A

Mucous is released by mucous cells in gastric glands. It forms a thick, alkaline layer that sticks to the epithelial cells. This protects the epithelial cells.

22
Q

Name 3 toxins that damage the stomach wall

A

Alcohol- dissolves mucous layer
H. pylori- causes acute gastritis
NSAIDs- inhibits prostaglandins

23
Q

Where does food enter the stomach?

A

The oesophagus

Semester 3- GI (14 decks)

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