SECRETIONS Flashcards
3 pairs of exocrine salivary glands in the mouth
Sublingual glands
Submandibular glands
Parotid glands
Describe the products of the parotid, submandibular, and sublingual glands
Parotid (largest): serous cells –> watery secretion & amylase
Submandibular & sublingual: mixed mucous & serous -> saliva is more viscous w mucoproteins
Salivon
Unit of a salivary gland
- Acinus/end-piece
- Ringed by myoepithelial cells that contract it
- Intercalated duct & striated-appearing collecting duct
Functions of saliva & chewing
-
Defense
- Mouth cleaning
- Antibacterial
- Neutralization of gastric reflux
- Solvation facilitates taste
-
Lubrication
- forms small food particles & bolus
- aids in speech
-
Digestion
- initiates starch & lipid digestion
- initiates responses in more distal GI tract
Salivary constituents - defense functions
-
Mucus + water
- Lubrication against mechanical trauma
- Dilution of chemical components
- Bolus temperature control
- Oral hygiene
-
HCO3-
- Neutralize acids in foods & HCl from reflux
- Antibacterial; neutralizes bacterial acid
- Lactoferrin - antibacterial; binds iron
- Muramidase - antibacterial; hydrolyzes cell walls
- EGF - cell growth & repair
Digestive function of salivary constituents
- Water/mucus: lubrication of bolus
- a-amylase: starch digestion (optimal pH: 7)
- lingual lipase: fat digestion (optimum @ acidic pH)
What’s the function of R protein and kallikrein in the saliva?
Rprotein binds B12 and gets removed by pancreatic proteases; facilitates B12 binding to intrinsic factor
Kallikrein: increases blood flow to teh salivary glands by converting plasma kininogen to bradykinin
Whats the relationship between electrolyte concentration of saliva and its rate of secretion?
How does the fluid that enters the acinus differ from the fluid that actually ends up entering the mouth (ductular fluid)?
Fluid that enters the acinus is an ultrafiltrate of blood, so it has a similar electrolyte composition to blood.
As it progresses down the ducts, ductular cells modify it such that the secretion that ends up in the mouth is hypoosmolar and has more K & HCO3-
Acinar cell transporters
- Na largely diffuses through intercellular spaces and across tight junctions
- K, Cl, and HCO3- enter the acinus via channels in the apical membrane
What modifications occur to the primary acinus secretion?
Na & Cl leave
K+ & HCO3- enter
Still contains amylase from the primary secretion
How is hypoosmolarity achieved in the ductular fluid?
Apical cell membranes of ductular cells are water-impermeant –> Na and Cl absorption (quantitatively greater than K & HCO3- secretion) leaves the ductular fluid relatively dilute
Salivary secretion is regulated how?
NEURAL regulation - not hormonal
Initiated by
- sight or thought of food
- taste of food (activation of chemo & pressure receptors in mouth)
Both sympathetic and parsympathetic activity results in fluid secretion.
Whats the difference?
Sympathetic secretion: small amt of viscous muscoprotein-rich secretion; second msger is cAMP
Parasympathetic secretion: copious, watery, and protein-poor; second msger is Ca2+
Denervation of the ___ inputs to the salivary glands results in atrophy over time.
Parasympathetic because it’s responsible for enhancing blood flow to the gladn
Sympathetic innervation originates at ___ and goes to the ___ ganglion(s)
Paraysmpathetic innervation originates at ___ and goes to the ___ ganglion(s)
How do norepinephrine, Ach,andsubstance P all evoke salivary secretion?
- Norepinephrine –> intracellular cAMP release –> release of protein & amylase
- Ach –> intracellular Ca release –> fluid-rich acinar secretion
- Substance P : like Ach, but not as stimulatory
