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GI > Gastric Secretion > Flashcards

Gastric Secretion Flashcards

1
Q

What does the body of the stomach release and produce

A

Mucus
HCl
Pepsinogen
Intrinsic Factor

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2
Q

Describe the role of the antrum

A

Secretion of Gastin, and mixing/grinding of food.

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3
Q

Describe the role of the fundus

A

Storage

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4
Q

Describe the role of mucus in the stomach

A

Protection of the stomach wall

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5
Q

Describe the role of HCl in the stomach

A

Maintains acidity, activates pepsin and denatures proteins and bacteria

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6
Q

Describe the role of pepsinogen

A

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

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7
Q

Describe the role of intrinsic factor

A

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

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8
Q

What are gastric glands? What are their components?

A

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

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9
Q

What do chief cells produce

A

Pepsinogens

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10
Q

What do parietal cells produce

A

HCL

Intrinsic Factor

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11
Q

What do mucous neck cells produce?

A

mucous

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12
Q

Describe the Mechanism of Parietal Cells

A

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.

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13
Q

What is the typical pH of the blood

A

pH >7.4

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14
Q

What is the typical pH of the stomach

A

pH <2

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15
Q

Name the hormones regulating the digestive system

A 
Gastrin
Cholecytokinin
Secretin
Motilin
Gastric Inhibitory Peptide
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16
Q

What is the function of gastrin

A

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

17
Q

What stimulates release of gastrin

A

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

18
Q

What inhibits gastrin secretion?

A

Release of somatostatin and decrease of stomach pH.

19
Q

What releases gastrin?

A

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

20
Q

where are the majority of parietal cells found

A

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

21
Q

What three mechanisms controlling the secretion of gastric acid

A

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

22
Q

Mechanism of Vagus/Local Reflexes on gastric secretion

A

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

23
Q

Mechanism of Paracrine on gastric secretion

A

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

24
Q

Mechanism of endocrine system on gastric secretion

A

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

25
Q

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

A

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

26
Q

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

A

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

27
Q

What are ECL cells

A

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

28
Q

What triggers vagal/enteric reflexes in gastric secretion?

A

Distension of the stomach wall

29
Q

What is the function of secretin?

A

Decrease of gastrin and gastric acid secretion

30
Q

What stimulates release of secretin?

A

Acid in the duodenum

31
Q

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

A

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

32
Q

What are enterogastrones and name three

A

Enterogastrones are hormones released from the duodenal mucosa.

  • Secretin
  • Cholecystokinin (CCK)
  • GIP
33
Q

When are enterogastrones released?

A

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

34
Q

Purpose of enterogastrones

A

Inhibit gastric acid secretion

Reduce gastric emptying - inhibition of stomach motility & contraction of the pyloric spinchter

35
Q

Define Zymognen and their purpose in terms of pepsinogen

A

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

36
Q

What is the role of mucous

A

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

37
Q

What is the role of intrinsic factor

A

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

38
Q

Define pernicious anaemia

A

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

GI (20 decks)

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