Gastric Secretion

Question 1

What does the body of the stomach release and produce

Answer 1

Mucus
HCl
Pepsinogen
Intrinsic Factor

Question 2

Describe the role of the antrum

Answer 2

Secretion of Gastin, and mixing/grinding of food.

Question 3

Describe the role of the fundus

Answer 3

Storage

Question 4

Describe the role of mucus in the stomach

Answer 4

Protection of the stomach wall

Question 5

Describe the role of HCl in the stomach

Answer 5

Maintains acidity, activates pepsin and denatures proteins and bacteria

Question 6

Describe the role of pepsinogen

Answer 6

Secreted by the stomach wall, proeznyme of pepsin. Cleaved by gastric acid. Pepsin digests proteins.

Question 7

Describe the role of intrinsic factor

Answer 7

Binds to b12, in order to be absorbed in the small intestine

Question 8

What are gastric glands? What are their components?

Answer 8

Secrete gastric acid and protective mucous. Contain chief, parietal and mucous neck cells

Question 9

What do chief cells produce

Answer 9

Pepsinogens

Question 10

What do parietal cells produce

Answer 10

HCL

Intrinsic Factor

Question 11

What do mucous neck cells produce?

Answer 11

mucous

Question 12

Describe the Mechanism of Parietal Cells

Answer 12

H2O and CO2 are broken down into Carbonic Acid (H2CO3) via carbonic anhydrase (unstable compound).

Carbonic Acid breaks down to Bicarbonate (HCO3),and enters into circulation via a HCO3/CL paired transporter. It then follows it’s gradient into the stomach lumen

The H+ ion, enters the stomach lumen via K+/H+ paired transporter.

H+ and CL+ ions moved into stomach lumen (HCL)

Water also moves into the stomach due to the change in osmotic gradient.

Question 13

What is the typical pH of the blood

Answer 13

pH >7.4

Question 14

What is the typical pH of the stomach

Answer 14

pH <2

Question 15

Name the hormones regulating the digestive system

Answer 15

Gastrin
Cholecytokinin
Secretin
Motilin
Gastric Inhibitory Peptide

Question 16

What is the function of gastrin

Answer 16

Stimulation of gastric acid secretion (parietal cells). Increases gastric motility.

Question 17

What stimulates release of gastrin

Answer 17

Released in presence of peptides and amino acids in the stomach lumen, increased stomach pH

Question 18

What inhibits gastrin secretion?

Answer 18

Release of somatostatin and decrease of stomach pH.

Question 19

What releases gastrin?

Answer 19

Gastrin is secreted by G cells into circulation and carried to the gastric fundus and cardia.

Question 20

where are the majority of parietal cells found

Answer 20

The majority of paritetal cells are found within the cardia and fundus of the stomach

Question 21

What three mechanisms controlling the secretion of gastric acid

Answer 21

Neurocrine (vagus/local reflexes)
Endocrine (gastrin)
Paracrine (histamine)

Question 22

Mechanism of Vagus/Local Reflexes on gastric secretion

Answer 22

Acetyl Choline –> increase of intracelluar Ca+, activation of protein kinases, activation of K/H pump

Question 23

Mechanism of Paracrine on gastric secretion

Answer 23

Histamine - Paracrine, released locally to parietal cells, ATP–> cAMP, activate protein kinases, K/H pump

Question 24

Mechanism of endocrine system on gastric secretion

Answer 24

Gastrin - Increases intracellular Ca+, activating intracellular kinases, activating the K/H+ pump

Question 25

What effect does sight, smell and taste have on gastic acid secretion

Answer 25

Stimulation of the Vagus Nerve. This releases ACh and G cells

Question 26

What effect does the release of gastrin and ACh have on the paracrine system?

Answer 26

In ECL cells, gastrin and ACh secretion stimulate the release of histamine

Question 27

What are ECL cells

Answer 27

Enterochromaffin-like cell. Neuroendorcrine cells found in the gastric glands that release histamine

Question 28

What triggers vagal/enteric reflexes in gastric secretion?

Answer 28

Distension of the stomach wall

Question 29

What is the function of secretin?

Answer 29

Decrease of gastrin and gastric acid secretion

Question 30

What stimulates release of secretin?

Answer 30

Acid in the duodenum

Question 31

What triggers and what is the result of enterogastric (splaninc reflex)

Answer 31

When acid is detected in the duodenum, this causes a decrease in gastrin secretion and stimulation of parietal cells.

Question 32

What are enterogastrones and name three

Answer 32

Enterogastrones are hormones released from the duodenal mucosa. - Secretin - Cholecystokinin (CCK) - GIP

Question 33

When are enterogastrones released?

Answer 33

In response to acid, hypertonic solutions, fatty acids or monoglycerides in the duodenum, enterogastrones are released

Question 34

Purpose of enterogastrones

Answer 34

Inhibit gastric acid secretion | Reduce gastric emptying - inhibition of stomach motility & contraction of the pyloric spinchter

Question 35

Define Zymognen and their purpose in terms of pepsinogen

Answer 35

Inactive precursor. Stops autodigestion. Acidic pH creates the active form of pepsin that hydrolyes proteins. Neutral pH will denatutre pepsin. Therefore pepsin activation mirrors HCL secretion

Question 36

What is the role of mucous

Answer 36

Produced by the surface epithelia and mucous neck cells, mucous provdes a protective layer, from acid corrosion, pepsin digestion and mechanical injury

Question 37

What is the role of intrinsic factor

Answer 37

Required for vitamin b12 absoprtion. B12 forms a complex with intrinsic factor which can be absorbed in the illeum.

Question 38

Define pernicious anaemia

Answer 38

Those with pernicious anaemia have autoantibodies that attack intrinsic factor rendering them useless.