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GI Physiology Flashcards

1
Q

What cells make up a gastric gland?

A

Surface mucous cells
Mucous neck cells
Parietal cells
Chief cells

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2
Q

What do mucous neck cells secrete?

A

Mucus

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3
Q

What do chief cells secrete?

A

Pepsinogen

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4
Q

What do parietal cells secrete?

A

HCl and intrinsic factor

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5
Q

What is the mechanism for HCl secretion from parietal cells?

A

CO2 + H2O -> H2CO3
H2CO3 -> H + HCO3
H pumped out across apical membrane
HCO3 pumped out across basolateral membrane in exchange for Cl ion
CL leaves cell via apical membrane
H and Cl are in lumen of stomach with H2O

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6
Q

What transporter is essential for HCl secretion?

A

H+/K+ ATPase

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7
Q

What 4 factors act on H+/K+ ATPase to control gastric acid secretion?

A

Gastrin
Histamine
Prostaglandins
Acetylcholine

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8
Q

What is the function of Gastrin?

A

Binding to receptor causes increase in intracellular calcium.
Calcium acts on protein Kinase C which increases activity of ATPase

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9
Q

What is the function of Histamine?

A

Coupled to adenylate cyclase to convert ATP → cAMP.
cAMP acts on Protein kinase A to increase activity of ATPase

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10
Q

What is the function of ACh?

A

Binding to receptor causes increase in intracellular calcium.
Calcium acts on protein Kinase C which increases activity of ATPase

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11
Q

What is the function of prostaglandins?

A

Coupled up to adenylate cyclase to inhibit production of cAMP and switch the mechanism off.

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12
Q

What is the neurocrine control of gastric acid secretion?

A

Vagus nerve/ local reflexes

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13
Q

What is the endocrine control of gastric acid secretion?

A

Gastrin

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14
Q

What is the paracrine control of gastric acid secretion?

A

Histamine

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15
Q

What cells release histamine?

A

Enterochromaffin like cell (ECL)

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16
Q

What is the stimulation for histamine release?

A

Increased Gastrin/ ACh levels

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17
Q

What is the stimulation for ACh and gastrin release?

A

Increased vagal activity

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18
Q

What is involved in the cephalic phase for stimulating gastric acid production?

A

Sight/smell/taste of food

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19
Q

What is involved in the gastric phase for stimulating gastric acid production?

A

Distention of stomach
Peptides in lumen

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20
Q

What is involved in the cephalic phase for inhibiting gastric acid production?

A

Stopping eating

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21
Q

What is involved in the gastric phase for inhibiting gastric acid production?

A

Low pH due to HCl causes gastrin levels to lower

22
Q

What is involved in the intestinal phase for inhibiting gastric acid production?

A

Acid in duodenum -> enterogastric reflex and secretin release
Fat/CHO in duodenum -> HIP release
The result is reduced activity of G cells and parietal cells

23
Q

What are enterogastrones?

A

Hormones released from gland cells in duodenal mucosa
- Secretin
- Cholecystokinin (CKK)
- GIP

24
Q

What is the stimulation of enterogastrones?

A
  • Acid in duodenum
  • Hypertonic solutions
  • Fatty acids or monoglycerides in duodenum
    All signs that the stomach is emptying its contents
25
What is the action of enterogastrones?
- Inhibit gastric acid secretion - Reduce gastric emptying
26
What is intrinsic factor?
Glycoprotein released by stomach parietal cells to absorb vitamin B12
27
What is gastric motility?
The process by which food travels through the digestive tract via a series of muscular contractions called peristalsis
28
What produces gastric peristaltic waves?
Peristaltic rhythm (3/min) generated by pacemaker cells within longitudinal muscle layer
29
What is the impact of gastrin on motility?
Increased contraction
30
What is the impact of stomach wall distention on motility?
Reflexes cause increased contraction
31
What is the impact of Fat/acid/amino acid/hypertonicity in duodenum on motility?
Reduced contraction
32
What is the result of acid in the duodenum?
Vagal and ENS reflexes Secretin release from S cells The result is HCO3 secretion to neutralise the acid
33
What cells is HCO3 secreted from in the duodenum?
Brunner's glands in the submucosa
34
What are long and short reflexes?
ENS- short Vagal- long
35
What is the endocrine portion of the pancreas?
Pancreatic Islets Produce insulin, glucagon and somatostatin
36
What is the exocrine portion of the pancreas?
Acini -> Lobules -> intralobular ducts -> Main pancreatic duct -> common bile duct -> hepatopancreatic ampulla
37
What do acinar cells secrete?
Digestive enzymes
38
What to duct cells secrete?
Bicarbonate
39
What is the action of enterokinase?
Converts trypsinogen to trypsin
40
What is the action of trypsin?
Converts all other zymogens to active forms
41
What is secretin released in response to?
Acid in duodenum
42
What is Cholecystokinin (CCK) released in response to?
Fat/amino acids in duodneum
43
What is the mechanism for glucose transport?
SGLT1 undergoes conformational change when sodium and glucose bind Secondary active transport Creates osmotic gradient
44
What is the mechanism for fructose transport?
Facilitated diffusion through GLUT-5 and GLUT-2 No sodium involvement No water uptake associated
45
What is the mechanism for sodium transport?
SAAT transports sodium and amino acid across apical membrane Sodium independent transporter in basolateral membrane Creates osmotic gradient
46
What is PepT1?
Transports dipeptides and tripeptides via hydrogen ion dependant process
47
What are the fat soluble vitamins?
A, D, E, K
48
What are the water soluble vitamins?
B, C, folic acid
49
What doe sDMT1 transport?
Iron into the duodenal enterocytes
50
What do iron ions bind to?
Ferritin
51
What do iron in blood bind to?
Transferrin
52
What do iron in blood bind to?
Transferrin

Alimentary System (24 decks)

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