Lecture 30 - Monogastric Secretions (Oral, Gastric) Flashcards
what are the 4 functions of saliva
-moisten and lubricate bolus
-dilutes osmolarity of the ingested material
-digestion of carbs and fat
-anti-bacterial
what kind of cells are contained in salivary glands
acinar cells
what do acinar cells produce
proteins and antibacterial peptides
parasympathetic fibers have what effect on acinar cells and myoepithelial cells
- increase production of acinar cells
- contraction of myoepithelial cells
what do salivary ducts add
add an alkaline secretion
what is the effect of secretin on salivary duct cell secretion
increases
(lower/higher) pH in the duodenum increases secretin production
lower pH in the duodenum
what kind of drugs dry up secretions from the mouth
anticholinergic drugs
what toxin can make horses drool alot? by what mechanism?
toxin in mouldy red clover activates salivary muscarinic receptors
esophageal stomach is lined by what kind of epithelium
stratified squamous epithelium
is the esophageal stomach glandular or nonglandular
non glandular
does the esophageal stomach produce mucus, acid or enzymes?
no
is the cardiac stomach glandular
yes
what does the cardiac stomach produce and its function
mucus and buffer –> adheres to cells to protect epithelium from proteolytic enzymes and acid
is the fundic region of the stomach glandular or non glandular
glandular
what does the fundic region of the stomach produce
produces acid, proteolytic enzymes, hormones, mucus
which compartment of the stomach is generally the largest
fundic region of the stomach
is the pyloric region of the stomach glandular or non glandular
glandular
what does the pyloric stomach produce
produces mucus and buffer but not acid or proteolytic enzymes
what cells live in the pyloric region of the stomach
enteroendocrine cells and G cells that produce gastrin
what increases gastrin secretion from G cells in the pyloric stomach
high stomach distention and high stomach pH
what are gastric pits lined with
lined with mucus secreting cells at the luminal surface
what is the function of the mucus on the surface of gastric pits
forms a thick gel to protect stomach from acid and proteolytic enzymes
where does each gastric pit lead into
leads into a gastric gland: very deep invagination in the submucosa
function of chief cells
secrete proteolytic enzyme precursor pepsinogen into the stomach
describe the activation of pepsinogen
pepsinogen is cleaved into pepsin by HCl
what do chief cells also produce in neonates? what does it do>
also produces rennin in neonates, helps digest milk `
effect of rennin on milk
converts liquid milk to semisolid for longer residence in the GI and better absorption
what do parietal cells secrete? function?
acid to help hydrolytic breakdown of diet components and kills bacteria in ingesta
how are parietal cell proton secretions increased
Hormonal and parasympathetic efferent innervation
3 factors that activate mechanisms to increase proton secretions by parietal cells** (tAkE a DeEp BrEaTh:)
- histamine produced by ECL cells when gastric gland fluid pH is too high, histamine then diffuses to reach nearby parietal cells and binds to receptors on parietal cell (on basolateral side)
- hormone gastrin secreted into blood and reaches parietal cell on basolateral side
- increases in stomach distention and osmolarity which then increases vagal afferent to medulla and then vagal efferent stimulation of parietal cells increases (Ach working on muscarinic receptors)
describe the anticipation of food on vagal efferents to parietal cells
sight/smell/chewing/ swallowing of food increases parasympathetic activity which directly increases parietal and chief cell acivity
- increase in parasympathetic activity also increases gastrin secretion by G cells which then increases parietal and pepsinogen secretions
why are there multiple mechanisms in the control of acid secretion
ensure acid production by parietal cell can be increased on demand
mucous cells secrete…
mucus!!!! (shocker i know)
parietal cells secrete…
HCl
chief cells secrete…
pepsinogen
G cells secrete
gastrin
ECL cells secrete
histamine
how can epithelial cells lining the stomach get damaged
excessively low pH or other trauma
how do epithelial cells lining the stomach respond to damage
produce prostaglandin (requires function of cyclooxygenase (COX)-1
actions of prostaglandin
- reduce histamine and gastrin secretion by enteroendocrine cells (reduce acid secretion)
- increases mucus secretion by nearby epithelial cells
- increases blood flow to area: provides nutrients needed for rapid repair or replacement of damaged cells
what are ulcers
erosions of the mucosal lining of the GI system
clinical signs of GI ulceration
vomiting, anorexia, abdominal pain, weight loss
what enzyme is expressed in arthritic joints
COX-2
action of COX-2
catalyzes production of prostaglandins which are proinflammatory and activate nociceptors (pain) in affected region
COX 2 inhibitors are…
NSAIDs: ex. aspirin, Ibuprofen
COX 1 inhibitors
also NSAIDs :(
function of NSAIDs on COX-1
prevents prostaglandin production by cells that are damaged within the digestive tract (decreases tissue homeostasis and increases risk of ulcer development)
how can ulcers be treated
administer synthetic analogs of prostaglandins
carprofen
major COX 2 inhibitor (good for arthritic ouchies) with minor effects on COX1 activity (allows digestive tract to keep producing prostaglandins
what are other ways that ulcers can be treated
histamine receptor antagonists, muscarinic antagonists, proton pump inhibitors
