GI secretions P1: Salivary & gastric secretions Flashcards
(31 cards)
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
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
Dysfunction of saliva production:
Describe Xerostomia
Dry mouth-Lack adequate saliva, bacterial overgrowth and therefore dental caries
Organisation of salivary glands- acidic or alkaline
Alkaline
What are the 2 types of secretion
Sercus- main type of protein secreted is pyalin-hydrolyses starch
Mucus- Mucin protein-lubricant-
What are 3 major salivary glands & % contribution
Submandibular-70%
Sublingual-5%
Parotid-25%
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
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
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
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
Origins: Exocrine and endocrine
exocrine- fondus/body-acid
endocrine-hormone-/antrum/gastrin produce
What are the 2 functional regions of the stomach
Exocrine-consist of fundus and body
Endocrine
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
Structure and func of gastric gland -exocrine
Parietal- acid secretory & intrinsic factor IF
Histamine cells
Are there a lot of parietal cells in endocrine region
A few
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
Dysfunction of gastric mucosa: Gastritis?
Inflam by bacteria- Helicobacter pylori
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
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
Dsyfunction of proton pump
Inhibitors such as omeprazole, binds irreversibly to H+/K+ ATPase pump
Regulation of secretion-what stimulates secretion p1
Cephalic nerve-neural
Gastric-antral distention,
Interstitial- Proteins present - increase gastrin produce
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
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.
Autoimmune disease
Autoimmune atrophic gastritis: antibody mediated destruction: leads to hypochlorhydria
