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Physiology with pharmacology - L1 > Gastrointestinal tract secretions > Flashcards

Gastrointestinal tract secretions Flashcards

1
Q

How many litres is absorbed by the small intestine?

A

9 litres

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2
Q

How does the GI tract regulate the ECF volume?

A

Na+ is taken up by GI tract

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3
Q

What are the 3 main functions of the stomach?

A
  1. secretion
  2. motor - regulate food intake, mixing chyme, decrease food size
  3. humoral - gastrin, somatostatin
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4
Q

What are proximal secretions?

A
  • HCI
  • Pepsinogen (cleaved into pepsin (protease))
  • intrinsic factor
  • mucins/bicarbonate ions
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5
Q

What are distal secretions?

A
  • gastrin
  • somatostatin
  • pepsinogens
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6
Q

How many litres does the mucosal layer of the stomach secretory cells?

A

2L/day

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7
Q

What is basal secretions rich in?

A

rich in H+

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8
Q

What are the different cells & their secretions in the oxyntic glands?

A
  • Epithelial cells - HCO3
  • Mucous neck cells - mucus
  • Parietal cells - HCI, intrinsic factor
  • Chief cells - pepsinogen
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9
Q

How is the pyloric glands different from the oncotic glands?

A

pyloric glands don’t contain parietal cells

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10
Q

What does intrinsic factor absorb?

A

Vitamin B12

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11
Q

Describe resting parietal cells

A
  • cytoplasmic pool of tubulovesicular membrane in apical side
  • contain acid secreting H, K-ATPase
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12
Q

Describe the cytoskeletal changes when a parietal becomes active

A
  • fusion of tubulovesicular & canalicular membranes]- 50-100x increase in surface area
  • microvilli appearance
  • insertion of H, K-ATPase pump, K+ + Cl- channels
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13
Q

What is the major function of parietal cells?

A

gastric acid secretion

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14
Q

What channels are found on the apical side of a parietal cell?

A
  • H-K ATPase
  • chloride channel
    (HCl secretion)
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15
Q

What channels are found on the basolateral side of a parietal cell?

A
  • Na-K ATPase
  • HCO3 & Cl channel
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16
Q

What stimulates ATPase releasing HCl acid?

A

the release of acetylcholine via the vagus nerve

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17
Q

What do ECL cells release?

A

histamine, stimulating the H2 receptor, stimulating the H-K ATPase

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18
Q

What can stimulate H+?

A

Histamine (ECL), ACh (vagus), gastrin (G cells)

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19
Q

What inhibits gastrin?

A

low pH, therefore downregulating H+ secretions

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20
Q

What similarity do SI & LI structures have?

A
  • crypts of Leinerkuhn (SI - microvilli)
  • absorpb fluid & electrolytes via villus cells/surface epithelia respectively
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21
Q

What do crypt epithelial cells secrete?

A

fluid & electrolytes (Protective-bacteria/toxins)

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22
Q

What is the difference in net absorption/secretion between the small & large intestine?

A

small - absorbs K+
large - secretes K+

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23
Q

Is paracellular movement passive or active?

A

passive - determined by tight junctions

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24
Q

Do the crypts cells secrete or absorb?

A

secrete

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25
Q

Do the surface cells secrete or absorb?

A

absorb

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26
Q

What can activate a chloride channel?

A

cAMP

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27
Q

What does the Na+K+Cl- cotransporter bring?

A

brings ions into cell from blood

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28
Q

What ATPase is in the intestine?

A

K-Na ATPase

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29
Q

What ATPase is found on the basolateral side of the jejunum?

A

K-Na ATPase

30
Q

What exchanger is found on the apical side of the Jejunum?

A

Sodium-Hydrogen exchanger

31
Q

What is different in the Ileum compared to the Jejunum?

A

ileum has a chlorine-bicarbonate exchanger

32
Q

What is the main role of the ileum?

A

net absorption of NaCl

33
Q

What is the main role of the jejunum?

A

absorption of Na & bicarbonate

34
Q

What do acinar cells secrete?

A

enzymes (CCK recs)

35
Q

What do centroacinar cells secrete?

A

isotonic aqueous portion, modified by ductal cells

36
Q

How is HCO3 secreted into pancreatic juice?

A

using Cl-HCO3 exchanger

37
Q

What is the net effect of the pancreas?

A
  • secretion of HCO3
  • absorption of H+ (acidification of pancreatic venous blood)
38
Q

What are ductal cells receptors for?

A

CCK, Ach + secretin, which will upregulate production

39
Q

What induces the synthesis if Na+ channels in the large intestine?

A

aldosterone

40
Q

Is K secreted or absorbed in the large intestine?

A

secreted

41
Q

What happens to the products of carbohydrases?

A

products absorbed into villus blood

42
Q

What happens to the products of proteases?

A

products absorbed into villus blood

43
Q

What happens to lipases + bile salts?

A

products into the lacteals within villus (part of the lymphatic system)

44
Q

How does glucose get reabsorbed?

A

facilitated diffusion (cotransported with Na+)

45
Q

How do proteins get absorbed?

A

travel as dipeptides or tripeptides, which have been broken down by peptidase.
- travels into the epithelial cell of SI, using facilitated diffusion & sodium as a cotransporter.

46
Q

How do micelles get transported across the epithelial cell of villi?

A

as chylomicrons

47
Q

What % of the pancreas does the islets of langerhans make up?

A

10-30% - 500,000

48
Q

What is the rest of the pancreas made of?

A

aciner & ductal cells - part of exocrine tissue that secrete enzymes, bicarbonate for digestion

49
Q

What are the islet main secretory cells?

A
  • beta cells (65%)
  • alpha cells (20%)
  • delta cells (10%)
50
Q

What are other cells found in the endocrine tissue?

A

F cells (polypeptide cells)
E cells
Enterochromaffin cells

51
Q

What do B cells secrete?

A

insulin

52
Q

What do A cells secrete?

A

glucagon

53
Q

What do D cells secrete?

A

somatostatin

54
Q

What do F cells secrete?

A

pancreatic polypeptide

55
Q

What do E cells secrete?

A

Ghrelin protein (stimulates hunger)

56
Q

How does blood distribute via fenestrated capillaries?

A

small arteries enter islet core

57
Q

What allows communication & control between B & A cells?

A

gap junction between B & A cells

58
Q

What does somatostatin do?

A

somatostatin is a power inhibitor of glucagon & insulin secretion

59
Q

What are islets innervated by?

A

adrenergic - sympathetic innervation
cholinergic - parasympathetic innervation

60
Q

How does glucose enter the B cells?

A

via GLUT2

61
Q

What are the 3 types of G-coupled receptors?

A
  • B adrenergic
  • Glucagon
  • Somatostatin A
62
Q

What does the activation of B adrenergic agonist & glucagon lead to?

A

upregulates - adenyl cyclase - leading to more - Exocytosis of insulin

63
Q

What does activation of somatostatin A & adrenergic lead to?

A

down regulation of adenyl cyclase, leading to less exocytosis of insulin

64
Q

What does insulin encourage?

A

the insertion of GLUT4 (allows for glucose uptake) in the membrane of cells

65
Q

What is the name given to the conversion of glucose to glycogen?

A

glycogenesis

66
Q

What happens to excess glucose?

A

it converted into adipose tissue (lipogenesis)

67
Q

What 4 effects does insulin have on muscle?

A
  1. promotes glucose uptake
  2. promotes glycogen synthesis from glucose
  3. promotes glycolysis & carbohydrate oxidation
  4. promotes protein synthesis
68
Q

What is the action of insulin on adipocytes?

A
  • glucose converted into FA (fatty acids) - stored as triglycerides
  • insulin prevents lipolysis
69
Q

What are biguanide drugs?

A

drugs that up-regulate receptors on target tissues

70
Q

What drives the mensural cycle?

A

the hypothalamic-pituitary gonadal axis

Physiology with pharmacology - L1 (17 decks)

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