Salivary and gastric secretions Flashcards
3 types of salivary gland and what they secrete
parotid: secretes serous, alpha-amylase (ptyalin)
submandibular: secretes serous/mucin mix
sublingual: secretes mucin
Sjogrens syndrome
autoimmune disease that destroys exocrine glands
affects tears and saliva production
sicca symptoms: dry eyes and dry mouth
Xerostomia
lacks adequate saliva
dental caries and halitosis because of bacterial overgrowth
difficulty speaking/ swallowing solid food due to inadequate lubrication
Parasympathetic and sympathetic stimulation of saliva secretion rate
And what does stimulation of each cause
Para: sublingual/submandibular (CN VII) and parotid (CN IX) cause inc in amylase and mucin as well as vasodilation
Symp: stimulation causes dry mouth, inc amylase production but overall dec saliva
4 types of gastric gland cells
What do they secrete and what do they do
mucous neck cells: secrete mucous : protects surface epithelial cells from acid/ pepsin erosion
parietal cells: secretes HCl: converts pepsinogen to pepsin, hydrolysed fat and starch,and kills microorganisms
Secretes IF: binds to b12 for absorption in ileum and also involved in blood cell maturation in bone marrow. Absence results in pernicious anaemia
chief cells: secretes pepsinogen. HCl converts this into pepsin, an endopeptidase that cleaves peptide bonds at low pH.
endocrine cells
G cells - gastrin
D cells- somastatin
ECL cells- histamine
2 inhibitors of gastric acid secretion, and there effects
somatostatin( paracrine from D cells, endocrine from pancreatic islet cells) suppresses secretion of histamine from ECL cells, gastrin from G cells, and HCl from parietal cells
prostaglandin E2: inhibits histamine release at oxyntic cell by inhibiting cAMP
3 phases of gastric secretion
cephalic, gastric, intestinal
See notability for details
How is mucosa protected from acid
mucosal barrier created by surface mucous glands
mucus has basic side chains
HCO3- secreted by upper epithelial cells
both neutralise acid
also tight junctions prevent acid damaging underlying tissue
gastritis
inflamed gastric mucosa. most common cause is helicobacter pylori, but also smoking, alcohol, NSAIDs and chronic stress can cause it.
damaged surface epithelium leads to process called restitution
atrophic gastritis
autoimmune. antibodies cause destruction of gastric parietal cells. this leads to hypochlorydia (insufficient acid secretion) and deficiency of intrinsic factor (needed for B12 absorption)
What is general composition of saliva and it’s function
Composition: water, electrolytes , proteins (mucin, amylase, lipase, IgA, lysozyme and peroxidase )
Function: oral hygiene,lubrication digestion
How is hypotonic saliva formed in terms of primary and secondary secretions
What occurs when there’s a slower rate of saliva secretion vs a higher rate
Primary secretions: amylase, mucus, extra cellular fluid
Secondary secretion: na+/k+ exchange, passive cl-/hco3- exchange leads to formation hypotonic saliva
Slower: more hypotonic (more electrolytes reabsorbed)
Faster: closer to isotonic ,but still hypotonic.less electrolytes reabsorbed
3 ways gastric acid secretion is stimulated
1) parasympathetic ACh: vagus stimulates HCl, pepsinogen and mucus.
2) gastrin: main hormone responsible for HCl secretion by parietal cells.
3) histamine: secretes by ECL cells ( histamine release also stimulated by gastrin). Also causes paracrine stimulation of parietal cells leading to HCl secretion
How is HCl secreted into stomach. Talk in terms of pumps and exchangers
1) h+/k+ atpase = h+ secreted into canaliculus
2) cl-/hco3- = secretes cl- into canaliculus
H2O moves into lumen via osmosis
What is omelrazole, what does it do
Proton pump inhibitor, inhibits h+/k+ atpase irreversibly
