GI secretions P1: Salivary & gastric secretions Flashcards Preview

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Flashcards in GI secretions P1: Salivary & gastric secretions Deck (31):
1

What 3 processes does saliva do to food

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

2

Dysfunction of saliva secretion :
Sjoyrens syndrome-describe it

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

3

Dysfunction of saliva production:
Describe Xerostomia

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

4

Organisation of salivary glands- acidic or alkaline

Alkaline

5

What are the 2 types of secretion

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

Mucus- Mucin protein-lubricant-

6

What are 3 major salivary glands & % contribution

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

7

Structure and Composition: what is acinus

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

8

Describe func of Ductal cells

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

9

Central control of salivary glands

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

10

Gastric secretions: describe some and name

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

11

Origins: Exocrine and endocrine

exocrine- fondus/body-acid
endocrine-hormone-/antrum/gastrin produce

12

What are the 2 functional regions of the stomach

Exocrine-consist of fundus and body
Endocrine

13

Structure and func of gastric gland -endocrine

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

14

Structure and func of gastric gland -exocrine

Parietal- acid secretory & intrinsic factor IF
Histamine cells

15

Are there a lot of parietal cells in endocrine region

A few

16

Protection against self & mechanical damage
How?

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

Dysfunction of gastric mucosa: Gastritis?

Inflam by bacteria- Helicobacter pylori

18

Acid secretion -oxyntic cells-describe development of them

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

Acid Secretion-Parietal cell, describe process

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

Dsyfunction of proton pump

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

21

Regulation of secretion-what stimulates secretion p1

Cephalic nerve-neural

Gastric-antral distention,

Interstitial- Proteins present - increase gastrin produce

22

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

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

What are 2 major paracrine inhibitors:

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

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

24

Autoimmune disease

Autoimmune atrophic gastritis: antibody mediated destruction: leads to hypochlorhydria

25

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

Gcells of pyloris and Duodenum
Endocrine effect
triggered by peptides

26

What are effects of histamine and by what cells

ECL cells
Local Vasodilation
Paracrine effect

27

Vagal stimulation - regulation of gastric acid secretion
what does the corpus do

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

What do D cells inhibit

Somatostatin

29

IF PH is high what do D cells release

Somatostatin to inhibit G cells

30

Gastrin can activate receptors on which cells

D and G cells leading to release of

31

Antrum?

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