Stomach Histology&Physiology

Question 1

What are the two functional areas of the stomach?

Answer 1

Oxyntic Gland area (85%)

Pyloric Gland area (15%)

Question 2

What are the four histological layers of the body of the stomach?

Answer 2

Mucosa, submucosa, muscularis externa, serosa

Question 3

How does the muscularis externa of the stomach differ from that of the intestine?

Answer 3

Much thicker

Question 4

How do rugae differ from plicae?

Answer 4

Rugae are in the stomach, they direct food to the pylorus (longitudinal)
Plicae are in the intestine and slow food down (horizontal)

Question 5

What cells do you find in an oxyntic gland?

Answer 5

Mucus cells
Mucus neck cells
Parietal Cells
Chief cells
Inflammatory cells
Enteroendocrine cells

Question 6

What does the Parietal Cell secrete?

Answer 6

HCl-kills bugs, denatures protein, converts pepsinogen to pepsin
Intrinsic Factor-
Water-universal solvent

Question 7

What does a Chief Cell secrete?

Answer 7

Pepsinogen-converted to pepsin, digests proteins (vagally mediated)
Water-universal solvent

Question 8

What does a Mucus Cell secrete?

Answer 8

Mucus-protects mucosa
Bicarbonate-neutralizes acid
Water-universal solvent

Question 9

What does the secretion rate of ions depend on?

Answer 9

The oxyntic component

Question 10

What are the two types of gastric mucus?

Answer 10

MUC5AC-

MUC6

Question 11

What are the functions of trefoil proteins?

Answer 11

motogenic-promote migration of epithelium across injured mucosa
Tumor supressor-mutationseems to precede cancer formation

Question 12

What do G cells do?

Answer 12

Secrete gastrin into gastric antrum in response to:
AA and small peptides (phenylalanine and tryptophan).
Distention of the stomach.
Vagal stimulation mediated by GRP (gastrin releasing peptide.

Question 13

What does gastrin do?

Answer 13

increases H+ secretion by parietal cells.

Stimulated growth of the gastric mucosa.

Question 14

What inhibits gastrin secretion?

Answer 14

H+ in the lumen of the stomach

Somatostatin

Question 15

What do I cells do?

Answer 15

Secrete CCK in response to AA, small peptides, FA, and monoglycerides. Located in the duodenal and jejunal mucosa.

Question 16

What does CCK do?

Answer 16

Stimulates the contraction of the gallbladder and relaxation of the sphincter of Oddi. Stimulates pancreas to release enzymes. Inhibits gastric emptying. Stimulates growth of the exocrine pancreas.
Homologue of gastrin.

Question 17

What do S cells do?

Answer 17

Secrete secretin in response to H+ and FA in the duodenum.

Question 18

What does secretin do?

Answer 18

Stimulates release of HCO3 from pancreas and liver.
Increases bile secretion.
Inhibits H+ secretion by parietal cells.
Increases growth of the exocrine pancreas.
Homolog of Glucagon

Question 19

What is GIP and what does it do?

Answer 19

Glucose-dependant insulinotropic peptide.
Secreted by duodenum and jejunum in response to FA, AA, glucose in lumen.
Stimulates insulin release and inhibits H+ secretion.

Question 20

What are the GI paracrine hormones?

Answer 20

Somatostatin-inhibits the release of all GI hormones and H+ by cells throughout in response to H+ in the lumen.
Histamine-secreted by mast cells. Increases H+ secretion directly and by potentiating vagal stim. and gastrin secretion.

Question 21

What is VIP?

Answer 21

Vasoactive intestinal peptide.
Homologous to secretin. Released by neurons in SM and mucosa of GI tract.
Relaxes GI SM and LES, stimulates pancreatic HCO3 secretion, inhibits H+ secretion.

Question 22

What is GRP?

Answer 22

Bombesin is released from the vagus neurons that innervate G cells causing them to secrete gastrin. (Gastrin releasing peptide)

Question 23

How do enkephalins affect the GI tract?

Answer 23

Secreted by the nerves. Stimulate contraction of GI smooth muscle, inhibit intestinal secretion. This is why opiates stop you up.

Question 24

What mediates receptive relaxation of the stomach body and fundus?

Answer 24

Vagovagal reflex initiated by distention of the stomach and facilitated by CCK.

Question 25

How does the stomach mix food and what regulates it?

Answer 25

Slow waves at 3-5/min depolarize smooth muscle. Distal antrum closes causing retropulsion. Parasympathetic increases mixing, sympathetic decreases activity.

Question 26

What is the migrating myoelectric complex?

Answer 26

Mediated by motilin, every 90 minutes the stomach has a cleansing contraction. This also occurs in the small intestine but not in the large intestine.

Question 27

What mediates gastric emptying?

Answer 27

Tonicity of stomach contents (isotonic fastest). Fat and protein slow emptying by causing CCK release. H+ in the duodenum inhibits gastric emptying via direct neural reflexes conducted by interneurons in the GI plexus.

Question 28

What is the gastrocollic reflex?

Answer 28

stomach distention causes a rapid increase in large bowel motility and frequency of mass movements. It also causes a slower hormonally mediated response by CCK and gastrin.
One in. One out.

Question 29

What stimulates gastric H+ secretion?

Answer 29

Vagus nerve releasing ACh onto parietal cell M3 receptors and GRP onto G cells.
Gastrin hits CCKb receptor.
Histamine binds H2 receptors.
(gastrin, ACh, and histamine act synergistically potentiating eachsothers’ effect)

Question 30

What inhibits gastric H+ secretion?

Answer 30

pH<3 inhibits G cell gastrin release
Somatostatin-inhibit release of gastrin and histamine
Prostaglandin- inhibits adenylyl cyclase via Gi protein