Salivary function and secretion Flashcards
What are the 3 major salivary glands?
Parotid
Submandibular
Sublingual
What duct is related to the parotid gland?
Duct of Stensen
Where does the duct of stensen enter the mouth?
opposite second maxillary molar tooth
What is the duct of stensen otherwise known as?
Parotid duct
What duct is related to the submandibular gland?
Duct of wharton
What is a salivon?
The salivary functional unit
made up of secretory acinus and ducts
What is the secretory acinus?
The secretory cells which make the saliva
What are the major ducts sublingual glands?
Duct of Rivinus and common Bartholin
What does the salivary gland consist of?
An external capsule
Septae separating the tissue inside the glands into lobes and lobules
Lobules consisting of salivons
What cells surround the acini to secrete the saliva?
Myocontractile cells
What does a salivon consist of?
Secretory acinus
Intercalated duct
Striated duct
What is the route of fluid movement in the salivon?
Acinus -> Intercalated duct -> Striated duct -> Excretory duct
What do the striated ducts unite to form?
Interlobular ducts
Excretory ducts
What forms the acinus?
Pyramidal-shaped secretory acinar cells (the apex is directed into the lumen) - around the central lumen
What are the two types of acinar cells?
serous cells
mucous cells
Describe the serous cells
produce a watery solution rich in alpha amylase
contain small, dense, secretory granules
Describe the mucous cells
produce a thick mucous rich solution
large, pale, secretory granules
The order of structures in the salivon
contractile myoepithelial cells -> serous demilunes -> acinus (serous or mucous cells) -> intercalated duct -> striated duct -> excretory duct
What are the two stages of saliva formation?
1) Primary secretion by acinar cells
2) Seocondary modification by duct cells
What happens in the primary secretion part of saliva formation?
An isotonic solution compared to plasma formed due to the secretion of Na+, Cl- and H20 into the lumen from the acinar cells
What happens in the secondary modification part of saliva formation?
An hypotonic solution forms compared to the plasma due to secretion of K+ and HCO3- from the duct cell to the lumen and secretion of Cl- and Na+ (NOT WATER) into the blood vessel from the duct cell
Functions of saliva
lubrication protection digestion others: - secretions prior to vomiting - facilitates suckling by infants
What is the function of lubrication used for?
- aids movement
- facilitates speech
- helps chewing and swallowing
State 2 examples of why protection is important in saliva function
high calcium salt content helps to prevent demineralisation of tooth enamel
lysozyme attacks bacterial cell wall
State 2 examples of why digestion function is important in saliva
alpha amylase breaks down carbohydrates and then continues in the stomach
lingual lipase initiates fat digestion
What acinar cells are present in the parotid gland?
Serous cells
What acinar cells are present in the submandibular glands?
both serous cells and mucous cells
What acinar cells are present in the sublingual glands?
mainly mucous cells
As the flow rate increases, what is the effect on K+ and HCO3-?
HCO3- increases
K+ decreases
What cranial nerve supplies the submandibular and sublingual glands?
CN VII
What cranial nerve supplies the parotid glands
CN IX
Effect of parasympathetic stimulation on saliva secretion
increase synthesis and secretion of alpha amylase
increase fluid flow
increase contraction of the myoepithelial cells
increase blood flow to glands
Produces watery saliva
Which muscarinic receptors does ACh work on to cause saliva production down the parasympathetic route
M1 and M2
How does ACh effect the acini cells?
causes an increase in calcium concentration which drives fluid secretion in a complicated manner
Effects of sympathetic stimulation on saliva secretion
increase secretion of alpha amylase, K+ and HCO3-
increase contraction of myoepithelial cells
decrease blood flow to glands
Produces mucous thick saliva
What receptors mediate sympathetic saliva production?
a1-adrenoreceptors which increase [Ca2+]
b1-adrenoreceptors which increase [cAMP]
What is the effect of calcium on the sympathetic saliva production?
stimulate fluid secretion
What is the effect of cAMP on the sympathetic saliva production?
increases the production of protein
Is ENaC a voltage activated Na+ channel?
NO
What activates ENaC?
Aldosterone
How is an increase in [Ca2+]i produced?
Initiated by release of Ca2+ from the ER following activation of M1 and M3
Sustained by store-operated calcium entry (SOCE)
Which two receptors are activated by IP3
IP3R2 and IP3R3
How is IP3 formed?
Hydrolysis of PIP2
What causes IP3 generation?
Gq/11 coupling to M1 and M3 and PLCbeta3
Where does the initial signal of Ca2+ arise in the acinar cell?
apical pole
What type of messenger is IP3?
Secondary messenger
What is the effect of increased [Ca2+] on IP3 receptors?
As the concentration increases, there is an increase in the IP3 receptor activity to a peak and then it falls
What is the receptor on the ER responsible for Ca2+ release called?
Ryanodine receptor
What initiates SOCE?
Any stimuli which detect a depletion of the Ca2+ ER store, e.g.
- Any stimulus which generates IP3
- Pharmacological inhibition of SERCA
What detects a decrease in Ca2+ in the ER store?
STIMs
How are the ER stores refilled?
By SERCA
Example of an inhibitor of SERCA
Thapsigargin (Tg)
What type of STIM is in the salivary glands?
STIM1
What is STIM1
A calcium sensing protein
What happens to STIM1 when the ER stores are depleted?
undergoes a conformational change and they physically couple to the cells on the plasma membrane receptors
Which EF hand motif binds calcium in STIM?
Canonical EF (cEF)
Which EF hand motif does not bind calcium in STIM?
Hidden EF (hEF)
When calcium is present, what motif binds to EF when calcium is present?
SAM
What is puncta?
When in the absence of calcium, the STIM1 aggregates in the ER to the plasma membrane
What are the two components of the C terminus of STIM1?
Coiled coil 1 (cc1) and coiled coil 2 (cc2)
What is Orai1
A store operated channel
What does the STIM1 CC2 domain present to Orai1?
- STIM1 Orai-activating regions (SOAR)
- Calcium activating domains (CAD)
How does Ca2+ entry occur?
Through clustering of Orai1 channels close to the puncta
What is TRPC1?
A selective ion channel which conducts Ca2+ and is present on acinar cells
How is TRPC1 activated?
By the polybasic-rich K domain on STIM1
