SDL 2 - Face & Skull Flashcards
What are the three important groups of muscles in the head?
- Muscles of facial expression
- Muscles of mastication
- Extraocular muscles
Which nerve conveys cutaneous sensation from the face and forehead?
Trigeminal nerve
this is the 5th cranial nerve
Which division of the trigeminal nerve innervates which area of skin?
The divisions of the trigeminal nerve are:
- opthalmic branch
- maxillary branch
- mandibular branch
What are the important roles of the muscles of the face?
- Act as sphincters and dilators controlling the various openings
- Support the angles of the eyes and mouth
- Prevent secretions dribbling on to the face
- Play an important role in communication by changing the expression of the face
Label the important facial muscles
Which nerve innervates the muscles of facial expression?
Facial nerve
This is cranial nerve VII
What are the sensory and autonomic functions of the facial nerve?
Sensory:
- small area around the concha of the auricle
- Provides special taste sensation to the anterior 2/3 of the tongue
Autonomic:
- Supplies many of the glands of the head and neck, including:
- submandibular and sublingual salivary glands
- nasal, palatine and pharyngeal mucous glands
- lacrimal glands
What is the main function of orbicularis oculi?
It is a circular muscle that acts as a sphincter around the eye
It functions in closing the eyelids
Which 2 muscles act as dilators of the eye?
Dilator pupillae:
- causes the pupil to dilate when it contracts
Iris dilator muscle:
- causes dilation of the pupil, allowing more light to enter the eye
What complication is associated with paralysis of orbicularis oculi?
Inability to close the eyes can lead to the eye drying out
This results in pain, and blindness in extreme cases
Which muscle acts as a sphincter of the mouth?
Orbicularis oris
It’s action is opposed by a number of dilator muscles
How does the function of the buccinator muscle vary in neonates and adults?
neonates:
- it is used to suckle
adults:
- it is used in whistling and smiling
How does buccinator aid the muscles of mastication?
It pulls back the angle of the mouth and flattens the cheek area to hold the cheek to the teeth during chewing
The muscle keeps food pushed back on the occlusal surface of the posterior teeth when a person chews
What is the function of the parotid gland?
What is its position like?
It is the largest of the paired salivary glands
It occupies the interval between the mastoid process and the origin of sternocleidomastoid muscle posteriorly, and the ramus of the mandible , which it overlaps anteriorly
What covers the parotid gland?
It lies within the fascial parotid sheath
this is continuous with the investing fascia of the neck
Where is the parotid gland located?
In which condition does the parotid gland become swollen?
Why is it extremely painful?
Mumps
Swelling of the parotid gland is known as parotitis
it is painful as the parotid gland is invested in innervated fascia
What is the main function of the parotid duct?
Where does it open in the mouth?
It carries secretions from the parotid gland into the mouth
It passes through the buccinator muscle and opens into the vestibule of the mouth at the parotid papilla
This is the region between the cheek and the gums which lies across the second superior molar tooth
Which cranial nerve divides into its five terminal branches within the substance of the parotid gland?
Facial nerve
it divides the parotid gland into superficial and deep lobes
it lies superficially within the gland so is vulnerable to damage
In which two situations is the facial nerve (within the parotid gland) vulnerable to damage?
- Fracture of the temporal bone of the skull
- Benign or malignant tumours close to, or compressing, the facial nerve
What are the 5 branches of the facial nerve?
What (in general) do they supply?
Temporal branches:
- innervate frontalis, orbicularis oculi and corrugator supercilli
Zygomatic branches:
- innervate the orbicularis oculi
Buccal branches:
- innervate orbicularis oris, buccinator and zygomaticus
Marginal mandibular branches:
- innervates the mentalis
Cervical branch:
- innervates the platysma
What other 2 important structures lie within the substance of the parotid gland?
- Retromandibular vein
- External carotid artery
this is deep to the retromandibular vein, and divides into its 2 terminal branches within the substance of the parotid gland
What are the 2 terminal branches of the external carotid artery?
- Superficial temporal artery
- Maxillary artery
What are the branches of the external carotid artery?
What is the course of the hypoglossal nerve like?
It loops around the internal and external carotid arteries to run towards the tongue
What is the orbit?
Which bones of the skull are involved in its formation?
It is a bilateral cavity in the facial skeleton formed by 7 bones of the skull
- sphenoid
- zygomatic
- maxillary
- frontal
- ethmoid
- nasal
- lacrimal
Label the main foramina that form part of the orbit
Which cranial nerves (or branches) pass through these foramina?
Optic canal:
- optic nerve
Superior orbital fissure:
- superior and inferior divisions of oculomotor nerve (III)
- trochlear nerve (IV)
- lacrimal, frontal and nasociliary branches of opthalmic nerve (V1)
- abducens nerve (VI)
Inferior orbital fissure:
- zygomatic branch of maxillary nerve
Infraorbital foramen:
- infraorbital branch of maxillary nerve
What is the main function of the extraocular muscles?
They move the superior eyelids and eyeball
6 of the 7 muscles are involved in eye movement
The levator palpebrae superioris lifts the eyelids
What are the 7 extraocular muscles?
- Superior rectus
- Inferior rectus
- Medial rectus
- Lateral rectus
- Superior oblique
- Inferior oblique
- Levator palpebrae superioris
What are the functions of the 4 rectus muscles?
What is their innervation?
Superior rectus:
- elevates the eyeball
- supplied by oculomotor nerve (III)
Inferior rectus:
- depresses the eyeball
- supplied by oculomotor nerve (III)
Medial rectus:
- adducts the eyeball
- supplied by oculomotor nerve (III)
Lateral rectus:
- abducts the eyeball
- supplied by abducens nerve (VI)
What are the functions and innervation of the superior and inferior oblique muscles?
Superior oblique:
- inverts (medially rotates) the eyeball
- supplied by trochlear nerve (IV)
Inferior oblique:
- everts (laterally rotates) the eyeball
- supplied by oculomotor nerve (III)
What is the function of levator palpebrae superioris?
What is its innervation?
It lifts the eyelids
it is supplied by the oculomotor nerve (III)
What method is used to remember the innervation of the extraocular muscles?
The “chemical formula” LR6SO4
most muscles are innervated by CN III, except for Lateral Rectus and Superior Oblique
these are innervated by CN 6 and CN 4
Label the extraocular muscles
Label the extraocular muscles
Label the nerves which supply the extraocular muscles
Where does the trochlear nerve emerge from?
It is the only cranial nerve that emerges from the dorsal aspect of the brainstem
What are disorders of the trochlear, abducens and oculomotor nerves characterised by?
Diplopia - “double vision”
the simultaneous perception of two images of a single object
How would you examine whether the extraocular muscles were functioning properly?
Examine the patient’s eye movements
Have the patient look in all directions without moving their head and ask them if they experiences any double vision
What are the stages involved in testing eye movements?
Smooth pursuit:
- have the patient follow an object moved across their full range of horizontal and vertical eye movements
Convergence:
- have the patient fixate on an object as it is moved slowly towards a point right between the patient’s eyes
How is the oculomotor nerve individually tested?
Which muscles are being tested here?
- Ask the patient to look medially
- check that the upper lid is fully retracted on upward gaze
- Testing superior rectus, inferior rectus, medial rectus, inferior oblique and levator palpebrae superioris
What is the individual test for the abducens nerve?
What muscle is being tested?
Ask the patient to look laterally
This is testing the lateral rectus muscle
What is the individual test for the trochlear nerve?
What muscles are being tested?
- Ask the patient to look medially and then look downwards
- an isolated lesion of CN IV is very rare
This is testing the superior oblique muscle
What is ptosis?
Which muscles are malfunctioning in this condition?
Drooping or falling of the upper eyelid
This is due to dysfunction of the levator palpebrae superioris muscle (or the oculomotor nerve)
What is Horner’s syndrome?
It is a rare condition characterised by:
Ptosis:
- Drooping of the upper eyelid
Anhidrosis:
- Absence of sweating of the face
Enopthalmos:
- sinking of the eyeball into the bony cavity that protects the eye
Miosis:
- constriction of the pupil
It arises when the sympathetic trunk (a group of nerves) is damaged
Why does mild ptosis occur in Horner’s syndrome?
It is caused by a loss of sympathetic innervation to the eye
What are the 3 intraocular muscles?
- Ciliary muscle
- Sphincter pupillae
- Dilator pupillae
These intraocular muscles are within the eye
Label the intraocular muscles
The ciliary and sphincter pupillae muscles are supplied by the oculomotor nerve (CN III)
What are the functions of the intraocular muscles?
Sphincter pupillae:
- constriction of the pupil (miosis)
Dilator pupillae:
- Dilation of the pupil
Ciliary muscle:
- controls accommodation by altering the shape of the lens
Which autonomic ganglion controls the intraocular muscles?
They are under involuntary control and are supplied by the superior cervical ganglion
Ciliary and sphincter pupillae are supplied by parasympathetics from the oculomotor nerve
Dilator pupillae is supplied by sympathetics from the superior cervical ganglion
What is the temporomandibular joint?
Which actions does it permit?
It is a modified hinge synovial joint
It permits gliding, rotation, flexion (elevation) and extension (depression) of the mandible
What bones are involved in the formation of the temporomandibular joint?
It is formed by the articulation between the mandibular fossa of the temporal bone
and
the condylar process of the mandible
Label the structures surrounding the TMJ
How are the 2 articulating surfaces of the TMJ separated?
By the articular disc of the TMJ
This creates superior and inferior articular cavities
Label the features of the TMJ and the superior and inferior articular cavities
Why is dislocation of the TMJ not very common?
The joint is strengthened by ligaments
Dislocation is usually prevented by the articular tubercle
this is a bony structure which acts together with the ligaments to prevent dislocation
What is meant ‘protrusion’?
For the mouth to open the condylar process must glide anteriorly to lie directly beneath the articular tubercle
this is protrusion
What must occur in order for depression of the jaw to occur?
Depression is only possible once the mandibular condyle is fully protracted
What happens if depression occurs unilaterally?
The contralateral condylar process will undergo rotation on the inferior surface of the articular disc and grinding movements will occur
this movement is essential for grinding food between the molars
What muscles are involved in opening the jaw?
Depression of the mandible usually relies on gravity
the lateral pterygoid and the hyoid muscles can contribute to actively opening the jaw
What are the 4 muscles of mastication?
- Masseter
- Temporalis
- Lateral pterygoid
- Medial pterygoid
Label the muscles of mastication
Which muscles of mastication are responsible for the following movements?
What is the nerve supply to the muscles of mastication?
Trigeminal nerve (V)
What is the result of unilateral damage to the trigeminal nerve?
The jaw will deviate to one side when opened against resistance
If a unilateral lesion to the trigeminal nerve occurs on the left side, which side will the jaw deviate to?
Left side
Label the muscles of facial expression
What muscle pulls the scalp anteriorly?
What other actions is it involved in?
Frontal belly of occipitofrontalis
it also wrinkles the forehead and elevates the eyebrows
Which muscle pulls the scalp posteriorly?
Occipitalis
Which muscle closes the eye?
Which muscle acts alongside this muscle?
Orbicularis oculi closes the eye
Levator palpebrae superior contributes to the size of the aperture
What muscle is the sphincter of the mouth?
Orbicularis oris
This is known as the “kissing muscle”
Which muscle controls the aperture of the mouth?
Lip function is mainly controlled by the orbicularis oris muscle, which completely encircles the opening of the mouth, thus providing oral competence
Which muscle compresses cheeks against the teeth?
Buccinator
It is an assistant muscle of mastication and is used in neonates to suckle
Which muscle tenses the skin of the inferior face and neck?
Platysma
What is the passage of the parotid duct like?
It arises from the parotid gland
it travels anteriorly over the masseter muscle, to pierce the buccinator muscle
it opens (drains) into the mouth at the level of the 2nd upper molar
What is the innervation of the muscles of facial expression?
They are all innervated by the facial nerve (CN VII)
What are the branches of the facial nerve?
At which anatomical landmark does it split into its branches?
The facial nerve gives off branches to the muscles of facial expression at the level of the parotid gland
- Temporal
- Zygomatic
- Buccal
- Mandibular
- Cervical
- Posterior auricular
Label the branches of the the facial nerve
What are the major branches of the external carotid artery?
What is the relationship between the hypoglossal nerve and the carotid arteries?
It makes a 90 degree turn as it loops around the internal and external carotid arteries to run towards the tongue
What does the middle meningeal artery supply?
The dura mater and the calvaria
What 3 pulses can be felt in the face?
In which locations can they be palpated?
Temporal pulse:
- superficial temporal artery is palpated in the area anterior to the ear
- the anterior branch of the STA is palpated lateral to the eye and eyebrow
Carotid pulse:
- carotid artery is palpated at the angle of the mandible
Facial pulse:
- facial artery is palpated at the inferior border of the mandible
What are the 2 superficial muscles of mastication?
What are their origins and attachments?
Temporalis:
- originates from temporal fossa
- attaches to coronoid process of mandible
Masseter:
- originates from zygomatic process of temporal bone
- attaches to lateral aspect of ramus and angle of mandible
What are the 2 deep muscles of mastication?
What are their origins and attachments?
Lateral pterygoid:
- originates from the lateral aspect of lateral pterygoid plate
- attaches to condyloid process of the mandible
Medial pterygoid:
- originates from the medial aspect of the lateral pterygoid plate
- attaches to the medial aspect of the mandible
What muscles are involved in protrusion and retraction?
Protrusion:
- lateral and medial pterygoid
Retraction:
- posterior fibres of temporalis
- deep part of masseter
- geniohyoid and diagastric muscles
What muscles are involved in elevation and depression?
Elevation:
- temporalis
- masseter
- medial pterygoid
Depression:
- gravity
- diagastric, geniohyoid and mylohyoid
