salivary gland physiology Flashcards
how does saliva protect?
- pH control (buffer by HCO3)
- maintenance of mineralized surfaces (saliva is supersaturated with CaPO4–favors remin)
- lubrication and hydration–viscous solution coats and sticks to surfaces
- formation of enamel pellicle: layer of salivary proteins deposited on tooth surface–diffusion barrier, attachment of bacteria
how does saliva control oral microflora?
- direct killing: inhibition of bacterial, fungal growth, and possible antiviral activity
- agglutination and clearance by swallowing
- modulation of binding: favors attachment of benign species–have advantage over non-binding pathogens
taste and digestion of saliva
- implicated in taste perception
- hydrolysis of strach initiated
- protection against dietary components
blood clotting with saliva
reduced bleeding time in oral cavity, saliva accelerates clotting
protective components of saliva
- hypotonic mix of inorganic ions
- main buffering agent is bicarbonate
- supersaturated in calcium phosphate
- complex mix of over 50 proteins
mucins
large, hydrophilic, hydrated molecules
-provide viscosity, pellicle component, binding site for bacteria, facilitate clearance by agglutination
lactoferrin
binds iron
inhibits bacterial growth
lysozyme
antimicrobial
acts on cell wall
histatins
small histidine-rich peptides, powerful antifungals
lactoperoxidase
forms hypothiocyanite ion, highly toxic to bacteria
amylase
hydrolyzes starch
helps clear carbohydrate from teeth, may be antimicrobial
secretory IgAs
may bind bacteria and facilitate clearance
statherin
small tyrosine-rich peptide
inhibits spontaneous CaPO4 precipitation from saliva, could facilitate remin of small lesions in teeth
proline-rich proteins**
most abundant salivary protein (up to 70%)
bind dietary tannins
major pellicle components
control calculus
salivay glands are controlled mainly by—
parasympathetic signals
originate in superior and inferior salivatory nuclei in brain stem
many taste stimuli increase secretion —- fold basal rates
8-20
salivary glands secretion moderately increased by ____
sympathetic nervous signals
originate in superior cervical ganglia and travel alongside blood vessels to glands
gland secretion involves two integrated processes:
- production of a fluid
- secretion of proteins (mainly by exocytosis)
- different stimuli can elicit different mix of two systems
parasympathetic stimulation leads to production of saliva at a high flow rate but with a _______ organic content
lower
sympathetic stimulation leads to a relatively smaller increase of flow rate but more ____
viscous
how do neurotransmitters start salivary secretion?
bind to specific receptors on basolateral surface of acinar cells
trigger production of specific intracellular messages
-messages trigger production of fluid/ion secretion and exocytosis of proteins
sympathetic NT and receptor
norepinephrine (adrenergic) alpha adrenergic (alpha 1 is main) and beta adrenergic (beta 1 is main)
parasympathetic NT and receptor
acetylcholine–cholinergic
muscarinic
majority of protein synthesized and secreted by —
acinar cells
acini secrete approx isotonic mix of —–, ducts reabsorb —–, release —–
inorganic ions
ducts reabsorb Na+, Cl-
release K+
result is hypotonic solution
unstimulated saliva flow rate for submandibular and sublingual
~63%
0.04-0.40
minor gland secretion makes up for what percent of secretion?
10%
highly differentiated and polarized cells committed to production of proteins for exocrine secretion
acinar cells
- -extensive RER
- -large number of storage granules
protein synthesis in salivary glands
- stimulus dependent exocytosis of storage granules
- basal level exocytosis of storage granules
- immature granules provide 15% unstimulated secretion
4 & 5. low level constitutve epithelial pathways
two stage process of salivary fluid formation
- initially formed as nearly isotonic plasma-like secretion in acinar lumen
- modified in ducts by removal of Na+, Cl-, and addition of K+, HCO3- with no further secretion or absorption of water to produce hypotonic solution
steps for production of saliva
- stimulation from PNS
- acetylcholine muscarinic receptor
- M3 for stimulation of saliva (odd # stimulation)
- activate secondary messenger–diglyceride lipase
- want initial Ca release–bind channels–> open voltage gated channels–> influx of Cl-
adrenergic receptors
autonomic and bind to adrenaline and noradrenaline
sympathetic nervous system
adrenaline and noradrenaline
alpha and beta receptors
cholinergic receptors
autonomic receptors that bind to acetylcholine
parasympathetic nervous system
acetylcholine
nicotinic and muscarinic receptors
first stage for fluid secretion
cl- dependent
HCO3 dependent
four membrane transport systems of fluid secretion
- loop diuretic (furosemide, bumetanide)–sensitive Na/K/Cl ion cotransporter in acinar basolateral membrane
- basolateral Ca activated K channel (allows K OUT)
- basolateral Na/K ATPase (pumps Na out)
- apical Ca activated Cl- channel
in resting state, K and Cl—
concentrated in acinar cell above electrochemical equilibrium
- -K by Na/K ATPase
- -Cl by Na/K/Cl transporter
when stimulated by alpha adrenergic or cholinergic what happens
- intracellular Ca increases
- opens basolateral K channel; apical Cl- channel
- K+ exits cell basolaterally
- Cl- exits cell into lumen
- net neg charge in lumen
- Na+ follows Cl- by leaking from interstitium
- creates NaCl osmotic gradient
- causes transepithelial movement of water into lumen
cl-dependent secretion model
entry of Cl across basolateral membrane mediated by Na/K/Cl2 cotransporter and paired Na/H and Cl-/HCO3 exchangers.
-Cl exit across apical mem via Cl- channel
