Salivation Flashcards
list the 3 major salivary glands
parotid (largest)
submandibular
sublingual (smallest)
where is the parotid gland
- in posterior aspect of face anterior to external ear
- wrapped around posterior border of ramus of mandible (both superficial AND deep to it)
- lies on deep surface of mandible
what duct does the parotid gland have and where does this open into
- single discrete duct
- runs superficial to masseter muscle
- turns medially to pierce buccinator
- opens into vestibule of mouth
- opposite crown of upper 2nd molar
what is the structure and location of the submandibular gland
- horseshoe shape
- has intra oral (inferior to mucosa of floor of mouth) ad extra oral (palpated below lateral aspect of body of mandible and wraps around posterior border of mylohyoid muscle) parts
- wraps around inferior border of mandible
- surrounded by submandibular lymph nodes
what duct does the parotid gland have and where does this open into
- single discrete duct that runs anteromedially to open at sub-lingual papillae (projection in floor of mouth behind lower incisor)
- there are right and left papillae which receive ducts of the right and left submandibular glands respectively
where is the sublingual gland located
- between lateral surface of tongue and inner surface of mandible
- inferior to mucosa covering floor of mouth
what ducts does the sublingual gland have
- a SERIES of (15-20) DUCTULES which open along the length of the sub-lingual folds (in floor of mouth, seen if lift tongue up - pulled up by submandibular duct and mucosa covering them raised)
which other salivary glands do we have and where are these
- tiny accessory salivary glands
- embedded in mucosa of tongue, palate and lips
- supplied by entirely different set of nerves
how many cranial nerves are on each side of the head and neck and which types of fibres do they carry
12 (I-XII)
- some sensory and others motor
- most carry a mixture of the two (provide much of motor + sensory supply to innervation of head and neck region)
how do the cranial nerves emerge from the brain
leave skull through specific foramina / fissures
I (olfactory nerve) = most superiorly
- progressively more inferiorly
- XII (hyperglossal nerve) = most inferiorly
which cranial nerve is the only one to leave the head and neck region
- vagus nerve
- innervates structures in chest and abdomen
- latin vagrantis = wanderer
in contrast where do the spinal nerves emerge
- from spinal cord
- leave through spaces between vertebrae of the spinal column
which nerves stimulate secretion and which cranial nerves do the ones supplying the major salivary glands run in
- SECRETOMOTOR FIBRES
run in… - VII - facial nerve
- IX - glossopharyngeal nerve
why is the trigeminal nerve V also important despite not itself providing secretor motor fibres to salivary glands
- branches of it carry some of facial glossopharyngeal nerve fibres to their target glands
which system are nerve fibres causing salivary glands to secrete part of and what does this mean for secretion of the salivary glands
- parasympathetic nervous system (division of the autonomic nervous system - part of nervous system controlling functions we do not have voluntary control over)
- means we don’t have direct conscious control over it
what functions are parasympathetic nerve fibres associated with
- ‘rest-and-digest’
sympathetic division = ‘fight-and-flight’ - antagonistic
how are secretomotors innervated
- cranial nerves VII and IX provide motor innervation that stimulates salivation
what are swellings on nerves carrying autonomic nerve fibres called and where are they found
- autonomic ganglia
- where autonomic nerve fibres join other autonomic nerve fibres
- nerves inside these are structurally different to sensory nerve fibres
how are ganglia formed
- pre-ganglionic fibres (coming into ganglion) stop in the ganglion by making synapses (functional connections) with the cell bodies of the post-ganglionic nerve fibres (leaving)
why is the ganglion present
accomodates all cell bodies of the post ganglionic fibres (cell bodies = thicker than nerve fibres that come from them so take up a lot of space)
give an example of a sensory ganglion, what property do sensory ganglia have
trigeminal (contains all cell bodies of sensory nerve fibres carried in the trigeminal nerve and its branches)
- have cell bodies BUT no synapses present
describe the structure of a sensory nerve fibre and how this leads to the formation of a ganglion
- sensory receptor at peripheral end
- goes into CNS from periphery
- sensory nerves = many individual nerve fibres running in it
- each one = an individual cell SO each has a cell body (keeps nucleus, cellular apparatus)
- cell body = thicker so form ganglion when clustered in one place
describe the structure of an autonomic secretomotor fibre and how this leads to formation of a ganglion
- come out of CNS
- run towards periphery
- stops (doesnt go directly to organ its going to stimulate)
- so has a TERMINAL - makes a junction (SYNAPSE) with a 2nd nerve fibre on its cell body
- 2nd nerve fibre sends a process which goes to target organ (salivary glands)
what way does information travel in
a) sensory fibres - sensory ganglion
b) motor fibres - autonomic ganglion
a) periphery to CNS
b) CNS to target organ
what are synapses
junctions between terminal of preganglionic and cell body of postganglionic nerve fibres
how do some secretomotor fibres travelling to the salivary gland ‘hitch a lift’ to reach their destination and where does this happen
- inside branches of the trigeminal nerve (V)
- nerve supply to submandibular gland - VII (facial nerve) fibres travel in lingual nerve (branch of the mandibular nerve - 3rd division of trigeminal nerve)
- secretomotor supply is still supplied by facial nerve fibres they originated in
which cranial nerve does the parotid gland receive secretomotor innervation from
IX (glossopharyngeal)
describe the nerve pathway to supply the parotid gland
1) nerve fibres of IX emerge from medulla oblongata
2) IX emerges from cranial cavity through the jugular foramen
3) after emerging the tympanic nerve is given off (small branch) which goes back into the skull
4) tympanic branch passes through middle ear cavity while travelling through the bone
5) inside here it breaks up temporarily into the tympanic plexus located on medial wall of the cavity
6) nerve fibres come back together to form lesser petrosal nerve
7) lesser petrosal nerve leaves temporal bone to enter cranial cavity and runs under the brain before turning downwards and leaving the skull via foramen ovale
8) lesser petrosal nerve enters otic ganglion (autonomic) after leaving skull. here the preganglionic nerve fibres it contains end by making synpases with cell bodies of post ganglionic
9) post ganglionic nerve fibres join / ‘hitch a lift in’ the auriculotemporal nerve (branch of V3 mandibular nerve) which carries them to the parotid gland
10) when the fibres fire, the parotid gland secretes
why is the tympanic branch named as such
passes through the middle ear cavity which is found inside the temporal bone and contains the tympanic membrane (ear drum)
why is the lesser petrosal nerve named as such
“petrosal” as it initially travels through petrous part of temporal bone
what is the tympanic plexus
network of nerve fibres which the tympanic nerve break up into in the middle ear cavity
in addition to the petrosal nerve, which other nerve does the foramen ovale transmit
mandibular nerve (V3, 3rd division of trigeminal nerve)
in addition to the glossopharyngeal nerve, what else does the jugular foramen transmit
internal jugular veins
what is the otic ganglion
autonomic ganglion of the glossopharyngeal nerve secretomotor fibres
which 3 divisions does the trigeminal nerve give off
V1 - opthalmic nerve
V2 = maxillary nerve
V3 = mandibular nerve
what can be observed when the mouth is open and tongue raised
- frenulum (midline)
- duct of right and left submandibular glands opening on sublingual papilla and raising sublingual folds (floor of mouth)
which cranial nerve supplies the submandibular and sublingual glands
VII - facial nerve
describe the pathway of the facial nerve to innervate the submandibular and sublingual ducts
1) facial nerve leaves brainstem and travels through petrous part of temporal bone on way out of skull in here it gives off the chorda tympani (branch)
2) chorda tympani carries pre-ganglionic secretomotor fibres of the facial nerve out of the skull into the infra-temporal fossa
3) chorda tympani then joins the lingual nerve where pre-ganglionic fibres ‘hitch a lift’ to reach the submandibular ganglion
4) pre-ganglionic nerve fibres synapse with cell bodies of post-ganglionic inside the submandibular ganglion
5) post ganglionic fibres leave the submandibular ganglion and travel straight to sub-mandibular (next to) 6) some go to sublingual gland so jump out of submandibular and go through lingual nerve a little further
where does the chorda tympani travel initially
through the middle ear cavity
where is the infra-temporal fossa
medial to ramus of mandible
what is the lingual nerve (AND auriculotemporal nerve) a branch of
V3 mandibular nerve (3rd division of trigeminal nerve)
what is the facial nerve responsible for in the anterior part of the tongue
taste
sensory fibres travelling from anterior 2/3 are part of facial nerve and carry taste sensations (supply taste sensation and carry taste info back to brainstem)
where is the middle ear cavity located
enclosed inside petrous part of temporal bone
what can be seen inside the middle ear cavity
laterally = tympanic membrane with chorda tympani passing along its medial surface
medially = tympanic plexus with tympanic branch of IX going in and lesser petrosal nerve emerging
facial nerve = runs through embedded in bone and gives of chorda tympani behind the cavity
what does the thin nature of the tympanic membrane mean clinically
- chorda tympani visible when examining ear drum with an otoscope
what is the relevance of taste fibres travelling through the middle ear cavity in middle ear infection / heavy cold
sense of taste affected
what supplies sensory supply (taste sensation) to the anterior 2/3 of the tongue
sensory fibres of the facial nerve (initially travel in lingual nerve before leaving it to enter chorda tympani then join main part of facial nerve to get back to brainstem)
where do sensory nerve fibres supplying the anterior 2/3 run relative to the secretomotor fibres supplying the SM + SL glands
alongside but in opposite direction
what supplies general sensation (touch, temp) to the anterior 2/3 of tongue
lingual nerve (branch of V3 - mandibular nerve)
how are taste and general sensation provided to the posterior 1/3 of the tongue
BOTH by sensory fibres of the glossopharyngeal nerve
how do muscles of the tongue receive their motor supply
ALL from the hypoglossal nerve XII (runs under then into tongue)
- this is the ONLY function of XII
