Exam 4: Gastric Secretion

Question 1

What are the 3 muscle layers of the stomach?

Answer 1

Outer longitudinal layer
Middle circular layer
Inner oblique layer

Question 2

What is receptive relaxation?

Answer 2

When distention of the lower esophagus relaxes the LES and also orad stomach

Question 3

Other than receptive relaxation, what else relaxes the LES?

Answer 3

• Vasovagal reflex (afferent and efferents carried by vagus)

- VIP induced relaxation, released by vagus

Question 4

What are gastric pits also known as and where in the stomach are they found?

Answer 4

Aka oxyntic glands

In the body of the stomach

Question 5

Where in the stomach are pyloric glands found? What kind of cells do they contain?

Answer 5

Found in the antrum

Contain G cells and mucous neck cells

Question 6

Where are chief cells found and what do they secrete?

Answer 6

Body of stomach

Pepsinogen

Question 7

Where are parietal cells found and what do the secrete?

Answer 7

Body of stomach

HCL and intrinsic factor

Question 8

Who do G cells secrete?

Answer 8

Gastrin

Question 9

What do mucus cells secrete?

Answer 9

Mucus and pepsinogen

Question 10

What are the 4 major components of gastric juice?

Answer 10

HCL, pepsinogen, mucus, and intrinsic factor

Question 11

What does HCL in the stomach do?

Answer 11

Reduces the pH, activates pepsin, aids in protein digestion, and kills bacteria

Question 12

What does pepsinogen do in the stomach?

Answer 12

Digests proteins

**pepsinogen is inactive, pepsin is active

Question 13

What does mucus do in the stomach?

Answer 13

Protects the gastric mucosa from the corrosive actions of HCl

Question 14

What does intrinsic factor do in the stomach?

Answer 14

Necessary for absorption of Vitamin B12 in the ileum

Question 15

In the formation of HCl, what enzyme catalyzes the formation of H and HCO3?

Answer 15

Carbonic anhydrase

Question 16

Where does HCl formation take place?

Answer 16

Gastric parietal cells

Question 17

In HCL formation, after H is made via carbonic anhydrase, H is moved into the lumen in exchange for ** via **.
This is blocked by what drug?

Answer 17

K+
ATPase
Omeprazole

Question 18

How does Cl get into the gastric parietal cells, so it can ultimately move across the apical membrane and form HCl?

Answer 18

Cl is exchanged for HCO3 on the basolateral membrane

Question 19

What is the function of gastrin?

Answer 19

• stimulate acid and pepsinogen secretion
• stimulate growth of gastric and intestinal mucosa
• stimulate natural and intestinal motility

Question 20

Gastrin is released from G cells of the antrum when stimulated by what 3 things?

Answer 20

• small peptides and amino acids in the stomach
• distention of stomach
• vagal stimulation

Question 21

What inhibits gastrin release?

Answer 21

Low ph (<3), somatostatin, and PGE2

Question 22

What are the 3 things that stimulate HCl release?

Answer 22

1) Gastrin stimulates partial cells via CCKb receptor
2) Gastrin stimulates ECL cells which release histamine, which bind to an H2 receptor on parietal cells
3) ACh

Question 23

What is the treatment of H. Pylori?

Answer 23

Antibiotics (clarithromycin or amoxicillin)

Question 24

What kind of drugs are Cimetidine and Ranitidine?

Answer 24

H2 blockers

Question 25

What kind of drugs are omeprazole and lansoprazole?

Answer 25

PPIs

Question 26

What causes peptic ulcer disease?

Answer 26

- Excess acid secretion and/or damage to mucosal barrier (acid destroys mucosal cells and liberates histamine and histamine stimulates acid secretion - NSAIDS, inhibit COX and decrease PGs - H. Pylori infection

Question 27

What causes vomiting to occur?

Answer 27

- The diaphragm lowers to the inspiratory position and the glottis closes - abdominal wall muscles contract increasing intra-abdominal pressure - stomach, esophagus, and LES relax and stomach gets squeezed between diaphragm and viscera - UES relaxes and vomit is projected into mouth

Question 28

How do ECL cells play a role in HCl secretion?

Answer 28

Gastrin stimulates ECL cells, which release histamin, which binds to H2 receptors on the parietal cells

Question 29

How does Atropine block HCl secretion?

Answer 29

It blocks M3 receptors | -when the vagus nerve releases ACh, atropine blocks the receptor that ACh is supposed to bind to

Question 30

How is HCl secretion controlled in the cephalexin phase?

Answer 30

- PNS via the vagus directly stimulates parietal cells and also stimulates G cells to release gastrin - Gastrin conveyed by circulation, stimulates parietal cells

Question 31

What do the PNS nerves release in the cephalic phase that stimulate G cells to release gastrin?

Answer 31

Gastrin releasing peptide (GRP)

Question 32

What stimulates HCl release in the gastric phase?

Answer 32

- release of amino acids and small peptides from parietal cells - distention of the stomach by local and vagovagal reflex arcs - histamine via H2 receptors - Alcohol and caffeine

Question 33

Is more HCL release in the gastric or cephalic phase?

Answer 33

Gastric

Question 34

What is pepsinogen released from?

Answer 34

Chief cells

Question 35

What converts inactive pepsinogen to its active form pepsin?

Answer 35

Acid, optimum pH is 1.5-2 and is denatured at 7

Question 36

What is the function of pepsin?

Answer 36

Cleave proteins to peptides at aromatic links | -digests 10-20% protein in the typical meal

Question 37

What stimulates the release of pepsinogen in the cephalic phase?

Answer 37

Vagus nerve

Question 38

What stimulates the release of pepsinogen in the gastric phase?

Answer 38

Luminal HCl locally stimulates release Gastrin and secretin stimulate release

Question 39

What cells secrete gastric mucus?

Answer 39

Neck cells and surface epithelium

Question 40

Is gastric mucus acidic or alkalotic?

Answer 40

Alkaline- possess high bicarb level

Question 41

What stimulates mucus secretion?

Answer 41

PNS (Vagus), gastric distention, and PGs stimulate mucus and bicarb secretion

Question 42

What increases gastric mixing and emptying?

Answer 42

PNS stimulation, gastric distention, gastrin, and motilin

Question 43

What decreases gastric mixing and emptying?

Answer 43

-SNS stimulation, secretin, CCK, GIP, H+, digestion products of fats and proteins in the duodenum, and duodenal distention