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Physiology Alimentary System > Gastric secretion > Flashcards

Gastric secretion Flashcards

1
Q

What is secreted in the body of the stomach

A

Mucous
HCL
Pepsinogen
Intrinsic factor

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2
Q

What secretes Mucous in the stomach

A

Foveolar cells, found in the necks of the gastric pits (Mucous neck cells)

Mucus-secreting cells are the most abundant cell type in the stomach, giving indications of how important mucus is to the functioning stomach.

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3
Q

What cell secretes HCL

A

Parietal cells

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4
Q

What cell secretes pepsinogen

A

Chief cells

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5
Q

What cell secretes intrinsic factor

A

Parietal cells

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6
Q

What cell secretes Gastrin

A

G cells

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7
Q

What cells lie in the gastric pit

A

Surface mucous cells

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8
Q

What cells lie in the Gastric gland

A

Mucous necks cells
Parietal cells
Chief cells

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9
Q

What is the pH of the stomach

A

2

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10
Q

What is the pH of blood

A

7.4

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11
Q

How is HCL made in the stomach

A

Process involving carbonic anhydrase and carbonic acid

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12
Q

What pumps H ions out of the apical membrane of the gut cells

A

A hydrogen/potassium pump (uses lots of ATP)

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13
Q

How does bicarbonate exit the enterocyte

A

Through the baso-lateral membrane via a HCo3 / Chlorine pump.

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14
Q

What happens when Hco3 is dumped in blood after meal

A

Post prandial alkalosis

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15
Q

What controls the amount of HCL created by parietal cells (x4)

A

Gastrin
Histamine
Acetylcholine
Prostaglandins

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16
Q

What organs secrete gastrin

A

Stomach (antrum)
Pancreas
Duodenum

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17
Q

What increases the amount of gastrin secretion

A

peptides, amino acids and gastric distension
vagal stimulation by gastrin releasing peptide
epinephrine and calcium

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18
Q

What does gastrin act on?

A

CCKB gastrin receptors on the basolateral membrane of parietal cells

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19
Q

What happens when CCKB gastrin receptors on the basolateral membrane of parietal cells bind gastrin

A

Calcium is released into the cell which activates protein kinase C and increases activity of the Hydrogen/potassium pump.

20
Q

What causes the release of histamine in the stomach

A

Gastrin and acetylcholine

21
Q

What releases histamine

A

Enterochromaffin-likecells

22
Q

What are Enterochromaffin-likecells

A

A type of neuroendocrinecellfound in thegastricglands of thegastricmucosa beneath the epithelium, in particular in the vicinity of parietalcells, that aid in the production ofgastricacid via the release of histamine.

23
Q

What does histamine act on

A

The H2 receptors in the stomach

24
Q

What happens when histamine binds to the H2 receptors in the stomach

A

It activates g protein adenylate cyclase which acts on protein kinase C. This increases action of the H/Cl pump - increases Hydrogen

25
Q

What causes the release of acetylcholine involved in HCL secretion during the cephalic phase

A

Thinking, seeing, smelling, tasting FOOD

26
Q

What receptor does acetylcholine act on in the stomach to increase acid production?

A

The M3 receptor on the stomach (via long and short reflexes)

27
Q

What happens when acetylcholine acts on the M3 receptors of the stomach

A

Increases intracellular calcium which activates protein kinase C - this increases H/CL pump

28
Q

What effect do prostaglandins have on Hydrogen secretion

A

they inhibit it

29
Q

What receptor does prostaglandins act on

A

E3 receptors

30
Q

What happens when prostaglandins act on E3 receptors

A

It activates G inhibitory protein which turns off adenyl cyclase and reduces activity of the h/cl pump

31
Q

Where are prostaglandins found in the stomach

A

Prostaglandins are found in high concentration in the gastric mucosa and gastric juice.

32
Q

What 3 stimuli cause increased Hydrogen increase during the gastric phase

A

Distension of Stomach
peptides in the lumen
Gastrin + Acetylcholine

33
Q

How does distension of stomach increase acid production

A

It initiates a vagal/enteric reflex, releasing acetyl choline. This causes the parietal cells to release H ions

34
Q

How do peptides in the lumen increase acid production

A

They activate G cells which releases Gastrin which act on parietal cells

35
Q

How does gastrin and acetyl choline increase acid production together?

A

They both act on enterochromaffin cells causing them to release histamine which acts on parietal cells

36
Q

What Inhibits gastric acid secretion in the cephalic phase

A

When you stop eating it decreases vagal activity so Ach and H+ stops getting produced

37
Q

What Inhibits gastric acid secretion in the gastric phase

A

When the Ph gets reduced to a certain level due to an abundance of stomach acid, gastrin secretion gets reduced from G cells

38
Q

What stimulus reduces gastric acid secretion in the intestinal phase (x2)

A

Acid in duodenum

Fat/CHO in duodenum

39
Q

How does acid in duodenum inhibit gastric secretion

A

It triggers the enterogastric reflex and the release of secretin from S cells. The secretin produces bicarbonate, decreases gastrin secretion and stimulation of parietal cells.

40
Q

How does fat/CHO in the duodenum inhibit gastric secretion

A

It triggers the releases of Gastroinhibitory peptide (GIP)

This decreases gastrin secretion and hence decreases gastrin stimulation of parietal cells

41
Q

What is the collective term for an inactive precursor enzyme

A

Zymogen

42
Q

What activates pepsinogen

A

Low pH (<3)

43
Q

What lines the stomach surface

A

Gastric Mucous

44
Q

What produces gastric mucous in the stomach (x2)

A

Surface cells

Mucous neck cells

45
Q

What are 2 functions of gastric mucous

A

Protects against gastric acid corrosion

Protects from mechanical injury

Physiology Alimentary System (8 decks)

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