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104:theme 1 > GI secretions P1: Salivary & gastric secretions > Flashcards

GI secretions P1: Salivary & gastric secretions Flashcards

1
Q

What 3 processes does saliva do to food

A

Lubrications- moistening mouth, dissolve chemicals in food and easily swallow

Protection- Reduces adverse effects of oral bacteria

Digestion-Began breakdown of carbohydrates & fats via the enzymes alpha-amylase & Lingual lipase

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2
Q

Dysfunction of saliva secretion :

Sjoyrens syndrome-describe it

A

An autoimmune disease that destroys the exocrine glands and most commonly affects saliva: dry mouth and eyes-Sicca symptoms

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3
Q

Dysfunction of saliva production:

Describe Xerostomia

A

Dry mouth-Lack adequate saliva, bacterial overgrowth and therefore dental caries

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4
Q

Organisation of salivary glands- acidic or alkaline

A

Alkaline

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5
Q

What are the 2 types of secretion

A

Sercus- main type of protein secreted is pyalin-hydrolyses starch

Mucus- Mucin protein-lubricant-

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6
Q

What are 3 major salivary glands & % contribution

A

Submandibular-70%
Sublingual-5%
Parotid-25%

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7
Q

Structure and Composition: what is acinus

A

Contains a isotonic solution. Duct cells reabsorb Na+ & Cl- but are impermeable to water and therefore saliva is hypotonic

Na+ leaves via leaky tight junctions and cl- through chloride channels- accompanied by water

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8
Q

Describe func of Ductal cells

A

Removal of Na+ from saliva is upical Na+ channel
cl- through cl channels
no H20 accompanied as aqua porins aren’t expressed

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9
Q

Central control of salivary glands

A

Saliva-stim by thought
Efferent nerves-salivary glands via the ACH-muscarinic receptors.
Parasympathetic promotes watery secretion in acini
& increase blood flow

Salivary nuclei in pons & parasympathetic tone
Glossopharygeal and facial nerves

Sympathetic-increase amylase
but decrease blood flow

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10
Q

Gastric secretions: describe some and name

A

Water and electrolytes: To dissolve & dilute digested food
HCL: hydrolysis, fat & starch, antiseptic-microbes, converts pepsinogen into pepsin & provide optim PH
Pepsins: Secreted as inactive pepsinogens away from stomach, low PH activates it
Mucus+bicarb barrier: Protect surface of epithelial cells
Intrinsic factor: Glycoproteins bind B12, necessary for absorption in ileum; without this can develop anaemia

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11
Q

Origins: Exocrine and endocrine

A

exocrine- fondus/body-acid

endocrine-hormone-/antrum/gastrin produce

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12
Q

What are the 2 functional regions of the stomach

A

Exocrine-consist of fundus and body

Endocrine

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13
Q

Structure and func of gastric gland -endocrine

A

Endocrine:
Mucus cell- protective barrier
Endocrine cell: D cells, somatostatin-inhibit gastrin release/regulates
Chiet cells: Secrete pepsinogen, & activated by gastric acid= Pepsin
G cells- gastrin

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14
Q

Structure and func of gastric gland -exocrine

A

Parietal- acid secretory & intrinsic factor IF

Histamine cells

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15
Q

Are there a lot of parietal cells in endocrine region

A

A few

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16
Q

Protection against self & mechanical damage

How?

A

Mucous layer of polysaccharides & mucoproteins prevent mechanical damage

Mucin has basic side chains & HCO3- secreted from epithelial cells -neutralises H+ ions

Tight junctions-stop acid entry

Continual renewal

17
Q

Dysfunction of gastric mucosa: Gastritis?

A

Inflam by bacteria- Helicobacter pylori

18
Q

Acid secretion -oxyntic cells-describe development of them

A

Tubulovascular membrane contain H+ K+ ATPASE Pump, responsible for acid secretion

Upon stimulation, tubulovascular mem fuses into canalicular mem

Fusion, then insertion of pump and cl- channel into canalicular mem

19
Q

Acid Secretion-Parietal cell, describe process

A

Actively exchanges H+ for K+
Carbonic anhydrase generates H+ & HCO3-. H+ pumped across membrane by H+/K+ ATPase pump.
HCO3- exchanged for cl- in interstit space
Cl- diffuses down gradient helping gastric venous blood to be alkaline

20
Q

Dsyfunction of proton pump

A

Inhibitors such as omeprazole, binds irreversibly to H+/K+ ATPase pump

21
Q

Regulation of secretion-what stimulates secretion p1

A

Cephalic nerve-neural

Gastric-antral distention,

Interstitial- Proteins present - increase gastrin produce

22
Q

Regulation: Stim of acid secretion p2: what cells & substances are stimulated
& how are they related

A

Gastrin- G cells
Histamine - Mast cells-CAMP-Increase intracellular CA2+ in 1
Acetylcholine- from postsynaptic vagal fibres
acts on D cells to inhibit somatostatin

Both 1 and 3 are : ACH stimulates histamine and acid release in parietal cells

ACH and acid amplify histamine release from ECL cells and parietal cells

23
Q

What are 2 major paracrine inhibitors:

A

Somatostatin: Antral & oxyntic gland D cells & pancreatic islet cells

Prostaglandins- from mucosal cells- antag histamine, inhib CAMP production, Gastric parietal cells dysfunction.

24
Q

Autoimmune disease

A

Autoimmune atrophic gastritis: antibody mediated destruction: leads to hypochlorhydria

25
Q

What cells release Gastrin & area of cells-anatomy, what type of effect and triggered by

A

Gcells of pyloris and Duodenum
Endocrine effect
triggered by peptides

26
Q

What are effects of histamine and by what cells

A

ECL cells
Local Vasodilation
Paracrine effect

27
Q

Vagal stimulation - regulation of gastric acid secretion

what does the corpus do

A

via Ach, increases acid secretion via directly parietal cells, and indirectly via ECL and D cells (ECL increases acid secretion via histamine release, D cells inhibit somatostatin

28
Q

What do D cells inhibit

A

Somatostatin

29
Q

IF PH is high what do D cells release

A

Somatostatin to inhibit G cells

30
Q

Gastrin can activate receptors on which cells

A

D and G cells leading to release of

31
Q

Antrum?

A

via GRP, stimulates both G and D cells (increase gastrin, inhibit somatostatin)

Gastrin from antrum promotes acid secretion by two endocrine mechanisms:
Directly via parietal cells
Indirectly via ECL cells

104:theme 1 (6 decks)

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