Salivation and Gastric Function (2) Flashcards
Gastrin:
- What secretes it
- in response to what
- effects
- secreted by antral mucosal cells-G cells
- in response to food, distension, vagus
- inc acid secretion of parietal cells
- stimulates growth of gastric mucosa
Motilin:
- what secretes it
- when
- what are the effects
- secreted by mucosa of small intestine- M cells
- during fasting period
- promotes contractions in distal stomach and intestine to clear indigestible materials
Where is the digestion of carbs and lipids initiated?
in the mouth
amylase - carbs
lipase - lipids
Where is the digestion of proteins initiated?
stomach - pepsins
What type of secretions does the acinar of the parotid glands, submandibular, sublingual secrete?
parotid - serous rich in alpha-amylase
submandib/sublingual - mucous rich
What is the component of salivary secretion that converts starch to sugar at a pH of 7?
ptaylin
What is lingual lipase secreted by?
salivary glands on tongue
-breaks down triglycerides
What is sjorgren syndrome?
autoimmune disease - destroys salivary and lacrimal glands
- xerostomia - dry mouth
- dental carries, halitosis, difficulty speaking
What does aldosterone stimulate?
Na+ reabsorption, K+ secretion
What do the pits in the body of the stomach contain?
- mucous neck cells
- peptic of chief cells - pepsinogen, gastric lipase
- parietal cells - HCl and intrinsic factor
What is achlorhydia?
when gastric acid secretion is low
-destruction of parietal cells
What is deficient in pernicious anemia?
intrinsic factor
What type of glands does the antrum of the stomach have?
pyloric glands:
deeper pits
fewer peptic cells
no parietal cells
G cells - gastrin
D cells - somatostatin
When are pepsin most active?
below pH 3.5
How are pepsinogens activated to pepsins?
at pH of 5-3, pepsinogens are spontaneously cleaved of an N terminal activation peptide
What is a diffusion barrier in the stomach for H+ and pepsins?
mucus layer produced by surface cells
What happens if H+ penetrates into the gastric epithelium?
damages mast cells and histamine is released
-inflammatory response
What happens as a result of chronic NSAID usage?
erosive gastritis
-inhibit PG synthesis which normally mantains mucous barrier
What is the main driving force for HCl secretion by parietal cells?
H+ K+ ATPase at the luminal membrane
H+ into lumen, k+ into parietal cell
What other diffusion process occurs at the apical membrane of a parietal cell, besides the H+/K+ ATPase?
Cl- passively flows out into the lumen
What two pumps occur at the basolateral membrane of a parietal cell?
- Na”/K+ ATPase (3 Na+ out, 2 K+ in)
- HCO3-/Cl exchanger
(HCO3- into blood, Cl- into cell)
What does the final secretion of a parietal cell contain?
water
HCl 150 mEq/L
KCl 15 mEq/L
small amount of NaCl
What has a higher pH: gastric venous blood or arterial blood?
gastric venous blood
-alkaline tide
What does prolonged vomiting cause?
dehydration, alkalosis, hypoalkemia
