Oral Cavity, Mandible & Temperomandibular Joint Flashcards
What forms the lateral walls of the oral cavity?
- Buccinator: continuous with the superior constrictor at pterygomandibular raphé
- PMR: pterygoid plate of sphenoid → mandible (posterior to mylohyoid ridge)
What are tonsillar pillars?
- Palatoglossus - connects palate to tongue
- Palatopharyngeus - connects palate to pharynx
- Lie medial to the PM raphé & dominate the posterior border of the oral cavity
- Palatine tonsil lie between (hence name)
- Covered by mucous membrane
Discuss the tongue
Occupies the floor of the oral cavity
Anterior 2/3 - oral part:
- ‘Velvety’ appearance - covered in papillae
- Mostly filiform
- Fungiform interspersed, taste buds at base
Posterior 1/3 - pharyngeal part:
- Nodular due to the underlying lingual tonsils
Sensory innervation of the tongue
- Anterior 2/3: lingual n. (Vc) general sensation, chorda tympani - taste (VII) hitchhikes on lingual
- Posterior 2/3: glossopharyngeal nerve for both
Intrinsic muscles of the tongue
Longitudinal, transverse and vertical fibres
Change the shape of the tongue
Extrinsic muscles of the tongue
Change the position of the tongue
- Genioglossus: protrudes tongue
- Anterior part of the mandible
- Hyoglosss: retracts & depresses tongue
- Hyoid
- Styloglossus: retracts & elevates tongue
- Styloid process
- Palatoglossus: depresses palate
- Palate
Innervation to the muscles of the tongue
XII all except palatoglossus (pharyngeal plexus - X)
Discuss the floor of the oral cavity
Mylohyoid (n. to mylohyoid Vc) forms muscular sling
Attach to hyoid, inner surface of mandible & each other at midline raphé, has a free posterior border
Discuss the sublingual glands
Lie on the superior surface of mylohyoid & inner surface of the mandible
Open into the sublingual region via many small, short ducts
Discuss the submandibular glands
Lies in the submandibular fossa - two lobes
- Superficial lobe is grooved by the facial artery
- Separated from parotid by stylomandibular ligament
- Deep lobe passes around posterior border of mylohyoid with duct
- Open on papilla beside lingual frenulum
Innervation to the sublingual & submandibular glands
Parasympathetic secretomotor from CN VII → chorda tympani → submandibular ganglion
Issues which can arise in the submandibular gland
- Higher concentration of mucus, increasing viscosity/decreasing flow
- More likely to develop calculi & stasis
- Duct blockage causes swelling & pain
- Impacted calculus extracted transorally
Discuss the parotid glands
- Largest salivary gland
- In the retromandibular region, extending over the lateral surface of mandibular ramus & masseter
- Duct crosses masseter & pierces buccinator
- Drains opposite upper 2nd molar
Discuss the innervation of the parotid glands
- Parasympathetic from IX to otic ganglion
- Via lesser petrosal nerve (from tympanic n)
- Post-ganglionic branches join auriculotemporal nerve
Discuss conditions of the parotid gland
- Specific viral infection causes mumps
- Can spread to brain, pancreas & testes
- Orchitis & sterility in adult males
- Can spread to brain, pancreas & testes
- Tumours
- Benign (pleomorphic adenoma) often asymptomatic
- Malignant tumours are highly invasive and may involve VII
Describe the palate
Roof of the oral cavity, comprised of the soft & hard palates which are continuous with one another
Describe the hard palate
- Formed from palatine process of maxilla & horizontal plate of palatine bone
- Covered in mucous membrane
Describe the soft palate
Comprised of 5 muscles:
- Palatoglossus & palatopharyngeus raise the tongue & oropharynx, approximating the palate
- Control opening of the oropharynx
- Tensor palati tenses the soft palate
- Innervated by n. to medial pterygoid (Vc)
- Levator palati elevates the palate, closing the nasopharynx
- Muscular uvalae stiffens the uvula
Describe the temporomandibular joint
- Articulation of the tubercle on the inferior surface of the temporal bone with head of the mandible
- Synovial condyloid joint with fibrocartilage on its articular surfaces
- A fibrocartilaginous disc separates the joint into upper & lower cavities
Exhibits a combination of complexity, close-to-continuous use and a capacity for force & finesse
Discuss dislocation of the TMJ
- Dislocate anteriorly when mouth is opened wide
- Under light anaesthetic, mandible pressed down and back to click into place
What are the muscles of mastication?
- Masseter
- Temporalis
- Medial pterygoid
- Lateral pterygoid
Masseter
- Origin: zygomatic process of the maxilla & zygomatic arch
- Insertion: lateral aspect of ramus, & angle of mandible
- Action: elevates mandible
Temporalis
- Origin: inferior temporal line & temporal fossa
- Insertion: coronoid process & anterior border of mandibular ramus
- Action: elevates the manible (posterior fibres retract)
Medial pterygoid
- Origin: pterygoid fossa, medial surface of lateral pterygoid plate
- Insertion: medial surface of mandibular ramus
- Action: elevates mandible and produces lateral movement
Lateral pterygoid
Two heads (s) & (i)
- Origin: infratemporal fossa (s) & lateral surface of the lateral pterygoid plate (i)
- Insertion: articular capsule & disc of the TMJ (s) & pterygoid fovea on neck of the mandible (i)
- Action: protrudes and depressed the mandible
- (s) fibres stabilise TMJ
Discuss movement at the TMJ
Comprised of two movements:
- Gliding in upper compartment
- Hinge movement in lower compartment
NB: never entirely independent - depression/elevation use both equally but protrusion/retraction/grinding mainly gliding
Depression of the mandible
- Lateral pterygoids pull condyles forward
- Digastric & infrahyoid pull the body down
Passive depression assisted by gravity
Elevation of the mandible
- Masseter, temporalis, medial pterygoid
Protrusion of the mandible
- Both pterygoids
Retraction of the mandible
- Posterior fibres of temporalis
How are grinding and chewing movements produced?
- Grinding: alternating protrusion/retraction
- Chewing: mandible moved side-to-side
- Masseter/temporalis keep mouth closed
Discuss mandibular fractures
- 2nd commonest facial bone fracture (1st nasal)
- Force can transmit removing fracture from site of impact
- Multiple fractures more common than single site
NB: if fracture strong enough for mandibular fracture, can get c-spine injury: secure airway as priority
