saliva Flashcards
3 main saliavry glands
-submandibular
-parotid
-sublingual
Explain structure of salivary gland
Acinus–intercalated ducts–striated ducts–excretory duct
Acinar cells surrounded by myoepithelial cells-smooth muscle that can contract and influence rate of fluid secretion
-intercalated duct (contains smooth muscle that can constrict/dilate) controls rate of saliva secretion
-striated duct lined by columnar epithelial cells, then fluid flows to excretory duct
how much saliva a day
1,500ml/day
what does parotid secrete
25% serous
what does sublingual secrete
5% mucin
what does submandibular secrete
70% sero-mucin
what is acini
-Acini are epithelial glands that secrete fluid of primary secretion
-consists of water, inorganic ions and enzymes.
what is mucin
glycoprotien which forms viscous fluid mucous
what is salivon
-functional unit of salivary gland, consists of acini cells that drain into ductal system
what is serous
watery fluid containing proteins from srous cells
composition of ions in saliva
K+ AND HCO3- conc higher in saliva than plasma
Na+ and Cl- conc lower in saliva
what happens in secondary secretion
Na and Cl reabsorbed from duct
K+ and HCO3 secreted less
saliva and water
hypotonic-low osmotic pressure, low permeability to water, water not reabsorbed
How does sodium enter and leave
-sodium enters epithelium cells across apical membrane via EnaC channel (epithelial sodium channel)
-basolateral side, na exits by using sodium potassium pump
How does chloride enter and leave
-chloride enters by apical chloride bicarbonate exchanger, more chloride exits by basolateral membrane by chloride channel
How does bicarbonate enter and leave
-bicarbonate enters by apical bicarbonate chloride exchanger
How does potassium enter and leave
basolateral uptake of potassium via sodium potassium pump, exits by potassium hydrogen exhanger
What happens at high flow rate
At high flow rate, not enough time for secondary modification to take place so similar composition of plasma to primary secretion
What happens at low flow rate
-low flow rate, more time for secondary modification to take place so less NA and Cl as reabsorbed and more k as that secreted, hypotonic solution
How is HCO diff
-HCO is diff as transport influenced by stimulants of saliva secretion. Hco is alkaline e.g. when you need high fluorite as need more saliva to neutralise acid- high rates of flow, saliva quite alkaline and contains high levels of HCO to neutralise acid.
evidence for 2 stage hypothesis
-flow rate curves
-acinar/intercalated duct micropuncture
-transport properties of isolated, perfused ducts
-poly-lysin injection
How is salivary secretion controlled
Controlled by autonomic nervous system-divided into sympathetic and parasympathetic
how does parasympathetic stimulate saliva
copious flow of watery saliva and vasodilation
how does sympathetic stimulate saliva
small amount of saliva, rich in enzymes
Which part of brain helps with saliva regulation-what is mechanism
Salivary centre-part of brain that helps with saliva regulation
-detect signals which it acts on e.g. taste/smell (increase saliva secretion)
-stimulus can also come from higher brain centres (e.g. dehydration, fear decrease saliva)
-sends signal through symp/parasymp system to increase/decrease saliva
-to salivary gland
how is saliva stimulated?
-food in mouth leads to reflex stimulation
-thought of food
-prior to sickness-nausea
