Oral and Esophageal Physiology Flashcards
What is deglutition?
swallowing
What’s in saliva?
water
digestive enzymes (amylase, lipase, RNAse, DNAse)
mucins
defence molecules (lysozyme, IgA, lactoferrin, peroxidase, defensins)
growth factors
bicarbonate
sex steroids
Is saliva exocrine or endocrine?
mostly exocrine, but some may be secreted into the blood suggesting an endocrine role as well
Is saliva acidic or alkaline? hypertonic or hypotonic?
alkaline hypotonic
What cells control saliva flow rate?
myoepithelial cells
How does compositoin of saliva differ depending on what gland you’re looking at?
parotid is almost entirely serous
submandibular is mixed
sublingual is mainly mucous
What does ionic conentration of saliva depend on ?
flow rate
fast rate: saliva resembles plasma with higher HCO3
slow rate: duct has had time to make significant changes in ionic concentration but do not alter volume, so it sticks more HCO3 in exchange for Cl and more H in exhcnage for Na. THis is what makes it hypotonic
What are some stimuli that will trigger saliva production?
small, taste, sounds and sights via higher centers
pressure in the mouth
distention, esopahgitis and vomiting fmor lower centers
What are some stimuli that will inhibit saliva production?
sleep
fatigue
fear
(inhibit parasympathetics from the medulla)
What NTs does the parasympathetic nervous system act thorugh to increase secretion of saliva?
VIP and ACh on muscarinic receptors
What kind of saliva is promoted by parasympathetic stimulation?
watery saliva
What are some other things the parasympathetic system will promote in terms of saliva production?
- increased water saliva secretion
- increased enzyme and mucus secreiton
- increased rate of bicarb secreiton
- stimualtes glandular metabolism and growth
- increased blood flow to the gland
What NTs does the sympathetic nervous system work through to increased salivary secretion?
norepinephinr on beta1 and alpha1 adrenergic
What type of saliva is promoted by the SNS?
viscous saliva
What are some other things the SNS promotes in terms of saliva production?
- stimualtes secreiton fo enymes and mucous
- stimulates glandular metabolism and growth
- stimulates contraction of myofibrilblasts
- constricts blood vessels and decreases blood flow (this is why the saliva is viscous)
What activates the amylase in saliva? What does amylase do?
it’s activated by Cl- and hydrolyzes alpha14 glycosidic linkages in starch to release mono- and disaccharides
What will lingual lipase do?
start to break down triglycerides
Under what conditions will the digestive enzymes in saliva be increased?
during times of pancreatic insufficiency and neonates - if the pancreas isn’t gonna do it, someone has to…
In very general terms, how does taste happen?
taste ligands are dissolved in saliva and bind to recetors on the taste buds, activating G proteins and secondary messengers to trigger release of NTs onto primary sensory neurons
this signals taste to the nucleus tractus solitarius
Can you get absorption in the oral cavity?
very little nutrient absorption, but some drugs are absorbed buccally or sublingually - good for them because htey can avoid first past metabolism
What are some causes of xerostomia?
sjogren’s
lots of meds - muscarinic antagonists, decongestants, and antihistamines
head and neck radiation
dehydration
sialolithiasis
nerve damage related to injury or diabetes
postmenopausal hyposalivation
What are some consequences of xerostomia?
increased risk for opportunistic infections
halitosis due to production of hydrogen sulfide by bacteria and accumulation of dead cells
decrease in oral pH leading ot tooth decay
decrease in tasting ability
problems with speech
dysphagia promoting poor nutrition
How can we treat xerostomia?
sugar gree gum
artficiial saliva
swich meds
parasympathomimetics like pilocarpine (but avoid due to side effects)
What prevents the bolus from entering the nasal cavity?
the soft palate lifts up to close off the nasopharynx
