saliva + salivary glands Flashcards
give 4 functions of saliva
- lubricant
- oral hygiene
- maintaining oral pH
- release digestive enzymes
what is saliva used as a lubricant for (3)
mastication - chewing
swallowing
speech
how is saliva used in oral hygiene
wash
immunity - antibacterial/antiviral/antifungal
because it contains lots of lysosomes
buffer
what pH should oral pH be maintained at
about pH 7.2 (slightly alkaline)
how does saliva maintain oral pH
by the bicarbonate/carbonate buffer system for the rapid neutralisation of
acid
how is saliva involved in releasing digestive enzymes
salivary alpha amylase is released from the parotid gland for starch digestion
what is dysfunction of saliva associated with
oral pain
infections
increased risk of dental caries
flow rate of saliva
0.3 to 0.7ml per minute
daily secretion of saliva
800 - 1500 ml in adults from major and minor glands
pH range of saliva
from 6.2 to 7.4
2 types of secretion
serous
mucous
what is serous secrtion
alpha amylase for starch
digestion
what is mucous secretion
mucins for lubrication of
mucosal surfaces
what secretion does parotid gland do
serous
what secretion does submandibular gland do
both mucous and serous
what secretion does sublingual gland do
both mucous and serous
what are the 3 main major salivary glands
parotid
submandibular
sublingual
what secretion do minor glands do
predominantly mucous but some are serous
what is the only serous minor gland
Von Ebner’s
factors affecting the composition & amount of saliva produced (9)
- Flow rate
- Circadian rhythm (sleep cycle)
- Type & size of gland
- Duration and type of stimulus that causes saliva to be produced
- Diet
- Drugs
- Age
- Gender
- Time of day
what provides defences of oral cavity (3)`
- mucosa
- salivary glands
- palatine tonsils
how does mucosa provide defence of oral cavity
physical barrier
how do salivary glands provide defence of oral cavity
saliva washes away food particles which bacteria or viruses may use as metabolic support
how do palatine tonsils provide defence of oral cavity
act as the “surveillance system” for the immune system
how are salivary glands involved in immunity
salivary glands are surrounded by lymphatic system (linked to thoracic duct and blood) - which contains a broad range of functional immune cells
which glands are continuously active
Submandibular, sublingual & minor glands
what dominates unstimulated components of the salivary system
unstimulated components of the salivary system are dominated by submandibular
components
when is parotid gland the main source of saliva
parotid gland ONLY becomes main source of saliva when STIMULATED
what are salivary glands composed of
two morphologically and distinct epithelial tissues:
- acinar cells
- ducts
what are acinar cells
functional unit of a salivary gland
what are ducts
surrounded by acinar cells
they collect to form the large cut entering the mouth.
equipped with channels
and transporters in the apical and basolateral membranes enabling transport of fluid and electrolytes
the ducts are NOT just a plumbing system, they modify the electrolyte
composition of saliva
what are the 2 types of acini
- serous
- mucous
describe serous acini
- dark staining nucleus
- nucleus in basal third
- small central duct
what does serous acini secrete
water and alpha amylase
where is serous acini found
mainly in the parotid gland
describe mucous acini
- pale staining - “foamy”
- nucleus at base
- large central duct
what does mucous acini secrete
mucous (water & glycoproteins)
where is mucous acini found
submandibular & sublingual glands
what are the 3 types of ducts
- intercalated
- striated
- interlobar ( excretory)
what are intralobular ducts
they are divided into intercalated &
striated
what are intercalated ducts
short narrow duct segments with cuboidal cells that connect acini to larger striated ducts
what are striated ducts
- striated like a thick lawn
- major site for reabsorption of NaCl
- appear striated at basal end
- basal membrane is highly folded into microvilli (giving the duct its striated
appearance) for active transport of HCO3 against concentration gradient - the microvilli are filed with mitochondria for energy to facilitate the active transport
what do striated ducts secrete
HCO3- and K+ secreted
what do striated ducts absorob
Na+ and Cl- absorbed
describe concentration of final saliva
the epithelium of the ducts reabsorbs water so final saliva is hypotonic
(has less water in it so have a higher concentration of solutes (K+ & HCO3-)
what are the diseases and dysfunction of the salivary gland (6)
- xerostomia
- obstruction
- inflammation
- degeneration
- drug side effects
- cancer
what is xerostomia
dry mouth
what causes xerostomia
may be a consequence of cystic fibrosis or Sjorgren’s syndrome (autoimmune
condition where immune cells attack glands resulting in little or no saliva produced - affects mainly women)
most common causes:
- medication and irradiation for head and neck cancers
what causes salivary gland obstruction
saliva contains calcium and phosphate ions that can form salivary calculi - stones
where is salivary gland obstruction most common
most common in submandibular gland (80% incidence) - they block the duct at the bend around the round mylohyoid or at exit at the sublingual papillae
what causes salivary gland inflammation
- caused by infection secondary to obstruction
- infections caused by; mumps (viral infection) - results in fever, malaise, swelling of the glands
what is salivary gland degeneration
- complication of radiotherapy to head and neck for cancer treatment
- Sjorgren’s syndrome - mainly in post-menopausal females, also affects lacrimal glands (tears)
how do drugs cause salivary gland side effects
about 500 prescription drugs have a Sympathomimetic effect
act on NA receptors or inhibit parasympathetic action at ACh receptors
what happens if salivary output falls to
less than 50% of normal
flow
xerostomia - dry mouth
what happens if salivary glands have low lubrication
oral function becomes difficult
what results in dental caries
low natural oral hygiene - poor pH control
= accumulation of plaque
= dental caries or increases
incidence of opportunistic
infections especially fungal
e.g candida - thrush
how much of salivary flow do the 3 major glands contribute to
parotid, submandibular and sublingual contribute to 80% of salivary flow
how much of salivary flow do the minor
glands contribute to
minor salivary glands contribute to 20% of salivary flow
where are the minor salivary glands found
they are found in the submucosa or the oral mucosa of the lips, cheeks, hard & soft plate and the tongue
describe parotid gland
superficial triangular outline
between:
- Zygomatic arch
- Sternocleidomastoid
- Ramus of mandible
what is parotid duct also known as
Stenson’s duct
where is parotid duct
crosses masseter muscle and pierces through the buccinator muscle where it enters the oral cavity near the second upper molar
can be palpated a fingers breadth below the zygomatic arch
what provides sensory sympathetic innervation to parotid
the auriculo-temporal nerve
- a branch of the mandibular nerve
- (V3 -this division of the trigeminal nerve exits the skull through the foramen ovale)
what provides parasympathetic innervation to parotid
supplied by glossopharyngeal nerve (IX)
what does sensory sympathetic innervation do (parotid)
inhibits / minimises secretion
what does parasympathetic innervation do (parotid)
stimulates secretion
horizontal structure of parotid duct
horizontally it has a triangular outline with the apex on the carotid sheath
which structures pass through the parotid
- external carotid artery
- retromandibular vein
- facial nerve (VII - exits skull through the stylomastoid foramen) - supplies the muscles of facial expression
so the parotid capsule is very tough
what are parotid glands made up of
the parotid glands are entirely made up of serous acini with ducts interspersed
structure of submandibular gland
Two lobes separated by mylohyoid muscle
- larger superficial lobe
- smaller deep lobe in the floor of the mouth
describe the course of submandibular duct
begins in the superficial lobe,
wraps around the free posterior border of the mylohyoid,
then runs along the floor of the mouth and empties into the oral cavity at the
sublingual papillae - located
more posteriorly than the
sublingual gland
what is submandibular duct also known as
whartons duct
histology of submandibular gland
- mixed gland with serous & mucous acini
- some serous acini are arranged in crescent-shaped groups of glandular cells at the bases of mucous acini referred to as serous demilunes
what provides parasympathetic innervation to submandibular
supplied by the chorda tympani branch of the facial nerve (VII)
what provides sympathetic innervation to submandibular
supplied via the lingual nerve which is derived from the facial nerve (VII)
where are sublingual glands
located more anteriorly than the submandibular glands
located in the floor of the mouth between mylohyoid muscles and oral mucosa of floor of mouth
very close to the submandibular gland
how is saliva transmitted in sublingual glands
saliva is transmitted via the submandibular duct as well or small ducts that pierce oral mucosa floor of mouth
size of sublingual gland
much smaller than submandibular - but size is variable
histology of sublingual gland
mixed gland with both serous & mucous acini - but mainly mucous
what provides parasympathetic innervation to sublingual
supplied by the chorda tympani branch of the facial nerve (VII)
what provides sympathetic innervation to sublingual
supplied via the lingual nerve which is derived from the facial nerve (VII)
where are minor salivary glands concentrated in
in the; buccal labial, palatal & lingual regions
also found at; superior pole of tonsils (Weber’s glands), tonsillar pillars & at the base of the tongue (von Ebner’s glands - underlying circumvallate papillae)
why does each minor salivary gland have its own simple duct
because they lack a branching network of draining ducts so each salivary unit has its own simple duct
what does parasympathetic stimulation do in minor salivary glands
stimulates salivary secretion
what does sympathetic stimulation do in minor salivary glands
inhibits salivary secretion (but some baseline secretion)
