Label the structures of the skull
Label the base of the skull
Label the parts of the mandible
What causes a cleft palate
Failure of fusion of maxillary process and palatine bones
Structures passing through foramen ovale
lesser petrosal nerve
accessory meningeal artery
Structures passing through foramen magnum
Why is the pterion anatomically significant?
Junction of temporal, frontal, parietal and sphenoid bones
Located 4cm above zygomatic arch
Fracture at the pteryon can damage middle meningeal artery. Causes extradural haematoma.
Results in sudden death following trauma and concussion to the head.
Why is the sphenoid bone anatomically significant?
Median part contains the sella turcica which contains the pituitary gland.
Veins of the neck
Veins of the head
Air filled extensions of the cranial bones that open into the nasal cavities
Lined by respiratory mucosa, which is ciliated and mucus secreting. Innervated by branches of the trigeminal nerve [V].
4 locations - frontal sinus, ethmoid sinus, maxillary sinus and sphenoid
Clinical significance of paranasal sinuses
Infections of nasal cavity can spread to sinuses
Maxillary sinuses are most commonly infected. When mucus membranes are congested, drainage is obstructed. Can be cannulated and drained
Infection of ethmoidal cells may break through the fragile medial wall of the orbit. 'blowout fracture'. Severe infections may cause periorbital cellultis, and blindness if there is spread across to the optic nerve and opthalmic artery (close proxiimity)
Injury to the facial nerve or its branches produces paralysis of some/all of facial muscles.
Affected areas sag, facial expression is distorted.
Corneal ulceration, eyelid everts and there is inadequate lubrication and hydration of the cornea
Weakness of buccinator and orbicularis oris causes food to accumulate in oral vestibule
Displacement of the mouth causes food and saliva to dribble out of the mouth
Speech is impaired.
Modified synovial hinge joint. Formed by the head of the mandible, articular tubercle (temporal bone) and mandibular fossa. Covered by fibrocartilage.
Articular disc divides the joint cavity into two compartments. Joint capsule is loose and attaches around teh temporal bone and mandible.
The head of the mandible and articular disc move anteriorly on the articular surface until the head lies inferior to the anterior tubercle.
The head pivots on the surface of the articular disc. Allows opening and closing of the mouth and complex chewing or side-to-side movements of the lower jaw. Controlled by muscles of mastication
Dislocation of temporomandibular joint
Excessive contraction of the lateral pterygoids may cause the heads of the mandile to dislocate anteriorly by passing anterior to the articular tubercles.
Mandible remains depressed and the patient may not be able to close their mouth.
(lateral pterygoid controls protraction of mandible)
Part of the ethmoid bone, contains CNI Fracture to the base of the bone causes anosmia and can cause CSF to leak out through the nose due to ruptured meninges
Muscles of mastication
Muscles of facial expresson
Orbicularis oris - closes the eye, loss of function leads to absent blink reflex, ulceration or epiphora
Platysma - keeps skin of the neck taught, loss leads to drooping neck skin
Depressor Anguilla oris - draws corner of the mouth down and laterally, loss causes corner of the mouth to turn up
Zygomaticus major and minor - draws corner of the mouth up and laterally. Loss - drooping mouth, no smile
Mentalis - raises and protrudes lower lip.
Exit of cranial nerves
Joint between sagital and coronal sutures of the skull, anterior fontanelle in children
Branches of the facial nerve
Passes through the parotid gland and emerges as 5 main branches
Branches of external carotid artery
Main branches of the trigeminal nerve
Trigeminal nerve is the major general sensory nerve of the head. Leaves cranial fossa by passing over petrous part of temporal bone.
Three terminal divisions
Opthalmic nerve (V1) emerge from superior orbital fissure
Maxillary nerve (V2) emerge from foramen rotundum
Mandibular nerve (V3) emerges from foramen ovale
V1, V2 are sensory, V3 is mixed
Three foramen located on the anterior face trasmit branches of the trigeminal nerve.
V1 supraorbital, V2 infraorbital, V3 mental. All in a vertical line. Emerging nerve can be anaesthetised there.
Describe the function of the mandibular nerve
Largest division of trigeminal nerve, motor and sensory fibres. Branches of nerve originate in infratemporal fossa
Carries sensation from teeth, anterior 2/3 of tongue, lower lip, skin of the temple and lower face
Innervates muscles of mastication and tensor tympani
Mandibular nerve block
To anaesthetise the mandibular nerve, the anaesthetic is injected at the infratemporal fossa.
What are the effects of TMJ dysfunction?
Can cause pain that radiates to the regions supplied by the mandibular nerve (V3) - ear, temporal region, mandibular teeth.
Normally caused by bruxism
How to test motor nerves of CN V
Motor nerves travel with the mandibular branch to the muscles of mastication
- Ask patient to bite tongue depressors and asses marks
- clench teeth and feel masseter and temporalis
- jaw jerk for upper motor neuron lesions
- open mouth, mandible deviates towards weak side in unilateral lesion (lateral pterygoid)
How to test for sensory innervation of trigeminal nerve
Test innervation of facial skin up to the vertex (forehead, maxilla, mandible) individually with sharp/dull stimuli.
Note: Numbess in one division indicates a pathology after trigeminal ganglion. Metastatic cancer can spread to cervival nodes and compress inferior alveolar nerve causing a numb chin.
Look at anterior tongue for bite marks/ulceration
Changes in hearing (CN V3 innervates tensor tympani). Fasiculations may result from damage resulting in tinnitus/fluttering in the ear.
Describe how to test CN VII
Check for facial asymmetry of movement (upper motor lesion)
facial weakness (check facial expression - raising corner of mouth, keep lips closed)
change in taste over anterior 2/3 of tongue
hyperacusis (damage proximal to stapedius in middle ear)
loss of lacrimation
How do you test hypoglossal nerve?
Test movements of the tongue, a lesion will cause the tongue to deviate towards the affected side
Layers of the scalp
Skin contains sweat and sebacous glands, hair follicles, abundant blood and lymphatic supply
Connective tisue (dense, richly vascularised layer) supplied with cutanous nerves
Aponeurosis serves as the attachment for occipitofrontalis
Loose connective tissue is a spongy layer that allows free movement of the scalp
Periosteum is a dense layer of connective tissue continuous with fibrous tissue of cranial sututes.
Where is the danger area of the scalp?
Loose connective tissue layer.
Pus or blood spreads easily within it due to spaces in the tissue.
Infection can pass into the cranial cavity through emissary veins which pass through the skull to the intracranal sutures e.g. meninges and the dural venous sinuses
Cause of a black eye
Infection or fluid in the loose connective tissue can enter the eyelids and root of the nose because occipitofrontalis attaches to the skin and subcutaneous tissue.
Black eyes are caused by injury to the scalp or forehead. Ecchymosis develop as a reasult of extravasation of blood into the subcutanous tissue and skin of the eyelids
Inferior alveolar nerve block
Nerve passes laterally to the pterygomandibular fold in the oral cavity.
Danger triangle of the face
From the corners of the mouth to the bridge of the nose.
Drains venous blood into the cavernous sinus through the orbit to the cranium.
Infections can move from the nasal cavity into the cranium via this rout (very rare)
Inferior alveolar nerve block
Inferior alveolar nerve is a branch of V3 (mandibular nerve)
Enters the mandibular canal of the mandible to supply the lower teeth and emerges from the mental foramen to supply the chin and lower lip.
Passes lateral to pterygomandibular fold. Can be anaesthatised here.
Branch of mandibular nerve
Originates in the infratemoporal fossa and enters the mouth between medial pterygoid and the ramus of the mandible, then passes anteriorly under the oral mucosa inferior to the 3rd molar tooth.
Lies anterior to the inferior alveolar nerve
Provides sensory innervation to anterior 2/3 of the tongue, floor of the mouth andl lingual gingivae
Also carries parasympathetic fibres and taste fibres of the facial nerve fom the oral part of the tongue
N.B. at risk in dental extraction due to proximity to molar tooth
Briefly dsecribe the anatomy of the eye and orbit
The orbits are pyramidal bony cavities that contain and protect the eyeballs. Formed by frontal bone, ethmoid bone, zygomatic bone and maxilla. Spaces filled with fatty tissue.
Eyelids and lacrimal fluid secreted by lacrimal glands protect cornea and eyeball from injury and irritation. Fluid forced out of lacrimal glands and spread over the eye when eyelids close.
Internal transparent mucosa of the eyelids forms superior and inferior conjunctival fornices. Eyelids strengthened by dense connective tissue (tarsus). Tarsal glands produce lipid secretion which lubricates edges of eyelids.
Eyelashes lie in the margins of the eyelid and are surrounded by sebaceous ciliary glands.
Briefly describe lacrimal apparatus
Lacrimal glands secrete lacrimal fluid which is transported to the conjunctiva by lacrimal ducts when the eyelid blinks.
Lacrimal fluid containing debris is pushed towards the medial angle of the eye towards the lacrimal sac. From here the nasolacrimal duct sweeps lacrimal fluid to the inferior meatus of the nasal cavity where it flows into the nasopharynx and is swallowed.