Lecture 8- COPY Flashcards
(30 cards)
contents of saliva
EMSL
Electrolytes: hypotonic high HCO3-
Mucins: lubricate bolus and enhance chewing action
Salivary amylase: initiates digestions
Lactoferrin: lysozyme with anti-bacterial action
major roles of the stomach
- reservoir
- adjust osmolality of conents
- antrum= grinding
- pylorus= regulates the size of particles
- secretion of acid
Gastric motility
- relaxation of fundus
- contraction of body and antrum
- pylorus contracts= to limit exit of chyme
- mixing by retrupulsion
what is required for normal gastric emptying
in tact antrum, pylorus duodenum
normal vagal function
normal hormonal function
(positive feedback from duodenum)
what causes delayed gastric emptying
diabetic gastroparesis
- due to autonomic neuropathy
- leads to variable rate of glucose absorption
- upper abdominal discomfort
drugs that delay gastric emptying
- eg anti-cholinergic drugs
what causes rapid gastric emptying
after gastric surgery
- “dumping syndrome” = nausea, vomiting, cramping, diarrhoea
- food moves too quickly from stomach to duodenm so are not completely digested
- undigested particles result in hyperosmolar chyme in small bowel
- this causes a rapid fluid shift into the gut causing intestinal distension=pain
- diarrhoea due to osmotic effect
drugs that speed up gastric eptying
- eg metaclopramide
what are the 4 types of cells in the stomach
parietal cells
ECL cell
G cell
D cell
what is the role of gastric acid in the stomach
- sterilise
- digestion (denatures proteins)
- helps with absorption of b12 and iron
what is achlorhydria
absent or low gastric acid
can be a result of pernicious anaemia
what kind of pump is in the parietal cells
H+/K+ ATPase proton pump
how do the proton pumps in parietal cells work
- H+ is actively pumped out of cells and into the stomach
- in exchange K+ enters the cell
- HCO3- is formed in the cell and transported out into the bloodstream
- in exchange Cl- enters the cell
- HCl formed
what reaction happens in the bloodstream with HCO3-
H2O + CO2 H+ + HCO3-
why does Cl- enter the cel after HCO3- moves out
to keep the pH and osmolarity in equilibrium
what happens when the parietal cell secretes HCl
the tubulovesicles fuse with canaliculus
increased SA and numbers of H+/K+ ATPase
increased acid secretion into gut lumen
what are the protection of the gastric mucosa from acid
mucus layer
bicarbonate secretion
autocrine
molecule that targets itself
paracrine
targets adjacent cells
endocrine
released into circulation to target distant cells
where are ecl cells located and what do they secrete
located in body of stomach
secrete histamine
what does histamine do
paracrine
stimulates acid secretion from adjacent parietal cells
what releases Ach
vagus nerve and enteric neurons
what does Ach stimulate
- parietal cells to stimulate HCl
- ECL cells to release histamine–> stimulates parietal
- G cells to release gastrin –> stimulates parietal and ECL
where are D cells located
in the antrum of the stomach
what do D cells do
secrete somatostatin which is paracrine and endocrine
- inhibit acid secretion by acting on adjacent G cells and inhibiting gastrin release