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