salivary gland Flashcards
what is the structural composition of salivary glands
- compound = made up of multiple secretory units with their tubules entering a main duct
- tubulo-acinar structures
what are the primary functional units of a salivary gland
1) combination of tubules
2) globe like secretory units called acini
what is the duct system
- modifies and transports the saliva to be finally secreted onto a free oral mucosal surface
- hence salivary glands are described as exocrine
describe the structure of a gland
- lobe on outside
- capsule
- septum (connective tissue between lobes containing blood vessels, nerves and collecting ducts)
- secretory units -> acinus -> intercalated duct -> striated duct -> collecting duct
what are salivary glands classified by
THEIR SECRETION
1) mucous (viscous) - mucin rich contains proteins linked to greater amnts of carbs
2) serous (watery) - protein rich
3) mixed
what are the 3 major salivary glands from biggest to smallest and their secretions
1) parotid = 100% serous
2) submandibular = 10:1 ratio s:m
3) sublingual = 10:1 ration m:s
what are the minor salivary glands
- smallest, discreet, contained throughout oral mucosa
- contained within
1) mucosa of lip (m)
2) cheek (m)
3) hard + soft palate (m)
4) tongue (s)
why is the tongue the exception to minor salivary glands being mucous
- GLANDS OF VON EBNER (in dorsum of tongue beneath circumvirate papillae) are minor serous producing
what is the composition of saliva
99% H2O
small amnt of inorganic and organic compounds
list the 7 functions of saliva
1) digestive
2) antibacterial
3) mineral protection
4) lubricant
5) taste
6) hormone production
7) maintenance of oral homeostasis
explain the digestive function of saliva
salivary amylase ptyalin
explain the antibacterial function of saliva
- lysozyme, histatins, antimicrobial peptides, antibodies
- combat bacterial colonisation by bacterial killing or inhibiting binding of bacteria to oral surfaces
- mucosal immunity by immunoglobulins (mainly IgA)
explain the mineral protection function of saliva
buffer HCO3 + mineral ions Ca + P
- mineral ions aid remin
- bicarbonate ions buffer plaque acid
- maintains integrity of enamel
explain the lubricant function of saliva
imp in
1) protection of oral mucosa (via mucin production)
2) food bolus formation
3) swallowing and speech
explain the taste function of saliva
- amylase / ptyalin brings substances into solution so they can be tasted
- solubisation of food substances so they can be transported to taste buds
explain the hormone production function of saliva
taste buds
explain the maintenance of oral homeostasis function of saliva
- by various proteins, enzymes, growth factors
- imp in wound healing
what system controls salivary secretion
AUTONOMIC NERVOUS SYSTEM
how does the ANS control salivary secretion
- BOTH sympathetic and parasympathetic fibres innervate the acini and act collaboratively in production of saliva during feeding
- afferent stimulation during mastication leads to reflex stimulation of salivary flow involving salivary centres
what is the exception to “normal” ANS control of salivary glands
MINOR SALIVARY GLANDS
- mucous secretion is entirely mediated by parasympathetic nerve impulses
what is the secretory element in parotid and serous part of submandibular, describe it
SEROUS ACINI
- globe shaped
- made of conically shaped secreting cells
- cells of acinus look granular as contain many secretory granules
what do the serous acini empty into
small INTERCALATED DUCT (lined with cuboidal epithelium)
what do intercalated ducts enter
larger STRIATED DUCT (still within secretory lobule)
describe striated ducts
- formed of columnar cells
- ‘striated’ because membrane furthest away from the lumen is thrown into numerous folds w many mitochondria
what do striated ducts empty into
larger secretory collecting ducts
what results in modification of saliva
active exchange across wall of striated duct
where are the glands of von ebner and what type of saliva are they
- embedded in muscle below circumvirate papillae which are found on dorsum of tongue and have numerous taste buds on their lateral borders
- TOTALLY serous - ONLY serous minor salivary glands
compare the size of the 3 main salivary ducts
a) parotid
b) submandibular
c) sublingual
a) largest
c) smallest
compare the secretion of the 3 main salivary ducts
a) parotid
b) submandibular
c) sublingual
a) serous
b) mixed, mainly serous
c) mucous
compare the ducts of the 3 main salivary ducts
a) parotid
b) submandibular
c) sublingual
a) intercalated, striated, collecting ducts end in single main duct
b) intercalated, striated, collecting ducts end in single main duct
c) FEW intercalated, NO striated, collecting ducts end in many ducts
compare the secretary action of the 3 main salivary ducts
a) parotid
b) submandibular
c) sublingual
a) nonspontaneous secretor
b) nonspontaneous secretor
c) spontaneous secretor
compare the solution type of the 3 main salivary ducts
a) parotid
b) submandibular
c) sublingual
a) hypotonic
b) hypotonic
c) isotonic
describe minor salivary glands
- classified by location in
1) submucosa: buccal, labial, palatal, palatoglossal, lingual - have collecting duct but intercalated and striated usually absent
what is the shape of mucous acini (in the sublingual gland + mucous part of submandibular)
in tube shape rather than spheres
what do mucous acini secrete into in the sublingual gland + mucous part of submandibular and what does this mean
- acini form their own duct system with no intercalated or striated ducts (acini -> secretory duct)
- means submandibular has less ducts than parotid overall
what is a frequent feature of mucous acini
- ‘cap’ of serous secreting cells called a SEROUS DEMILUNE
- formed by a cresent shaped collection of serous cells and surround the mucous acini which appears lighter when stained
- result of an artefact of preparation
what is initially generated by salivary gland acinar cells and what does this enable
lumen environment HYPERTONIC w respect to the adjacent blood capillaries + interstitial fluid
- enables movement of H2O into lumina
what type of saliva is generated by acinar lumen
ISOTONIC
what happens to isotonic saliva as it passes through the striated ducts
- rendered HYPOTONIC
- striated ducts are impermeable to H2O
- Na+, Cl and HCO3- are removed
what is the movement of water in the duct and why
- passes across cell membrane between adjacent cells
- as a result of Cl- secretion into the lumen
what is the movement of NaCl in the duct and why
resorbed out of the secretion by striated duct cells
describe how striated duct cells influence ion movement
- highly polarised
- their basal surface (adjacent to basal lamina separating it from adjacent connective tissue) shows numerous striations under light microscope
- its large SA supplied w high levels of energy from the mitochondria is involved in active transport
- they are the site of electrolyte resorption (esp Na+ + Cl-) AND secretion (K+ + HCO3-) without loss of H2O
what cells do secretory acinus contain
- serous
- mucous
- mixed
how can we distinguish secretory acinus from mucous acini
via morphology of their secretory granules
- dark granular appearance (w haematoxylin + eosin staining) resulting from no of refractile granules in luminal portion of the cell (adjacent to lumen)
WHEREAS mucous acini stain paler bc their mucin content doesnt readily take up routine stains
what do cells of the secretory acini have
- wedge shape outline
- basal surface broader, surrounds central lumen
- no of microvilli + infolding of cell membrane
- basal part of serous cell = separated from surrounding connective tissue by basal lamina
- luminal part of cell contains dense, round, secretory granules containing the packaged proteinacious components for release into the luminal system by exocytosis
