Salivary: Johnson Flashcards
Discuss the constituents and functions of saliva
Functions: lubricant; essential for speech, digestive (solubilizes food for tasting), protective for teeth (washes away food particles, releases fluoride), thermal buffer (allows you to drink hot stuff), raises pH of material for stomach, gets rid of noxious stimuli/tastes, increases prior to vomiting to prevent acid damage
Constituents: electrolytes (Na, K, Cl), water, and enzymes*
*Enzymes include: amylase (digests starch), lipase (digests fat), lysozyme (bactericidal), lactoferrin (precipitates iron to prevent bacterial growth), and IgA BP (forms secretory IgA, which is bactericidal)
Understand the formation of saliva
- salivary glands have a very high blood flow (about 20x that of muscle) and this determines the salivary flow rate
- saliva is elaborated from plasma by acini cells, and is transported and modified by the intercalated/striated ducts
- in the ducts, NaCl is absorbed*, K and HCO3 are secreted; cells are not very permeable to water so the saliva ends up being hypotonic (dilute)
- electrolyte concentrations will change with salivary flow rate: Na, HCO3, and Cl will increase with increasing flow rates, but K pretty much stays constant
- at extremely high flow rates, saliva approaches isotonicity
*This process is modulated by aldosterone which acts to conserve Na; it will increase absorption of NaCl and thereby H2O as well; ADH can also act here
Describe the regulation of salivary secretion
- all regulation is via ANS, with PNS providing the dominant tone
- stimuli (excitatory or inhibitory) reach the salivary nucleus in medulla, signal travels along CN7 and CN9 to the salivary gland; ACh is major NT; causes secretion, vasodilation, myoepithelial cell contraction, metabolism, and growth
- SNS also has inputs that originate in T1-3 and travel to the superior cervical ganglion; the to salivary gland where NE signals the same net effects as PSNS to the salivary gland (see above)
