4. Face, scalp, muscles of mastication Flashcards
Define the margins of the scalp?
The scalp consists of skin & subcutaneous tissue
FROM the superior nuchal line of the occipital bone
TO the supraorbital margins of the frontal bone
LATERALLY the scalp extends over the temporal fascia to the zygomatic arch
Margins of the face?
The face is the anterior aspect of the head from forehead to chin & from one ear to the other
Layers of the scalp?
SCALP
Skin: outermost layer
(Dense) Connective tissue: subcutaneous layer rich in neurovascular structures
epicranial Aponeurosis: suturing required to close gaping wounds
Loose connective tissue: separates scalp proper (1st 3 layers) from underlying pericranium & calvaria
Pericranium: external periosteal layer
In the epicranial aponeurosislayer of the scalp:
Which muscle and tendon is found here?
Issue with gaping wounds?
Tendon & muscle of occipitofrontalis (has frontal and occipital belly)
This layer prevents superficial wounds from gaping open; when this layer is compromised (e.g. laceration), gaping wounds result that require sutures to close
Between the aponeurosis & pericranium there are potential spaces for accumulation of fluid (e.g. blood) or spread of infection
Fluid/infection can spread to the eyelids or root of nose. why?
Frontal belly of occipitofrontalis inserts into skin & subcutaneous tissue not bone
Note: Fluid/infection do not spread posteriorly to the neck or laterally below the zygomatic arch
How do scalp infections spread to intracranial structures?
Via emissary veins
Which nerves innervate the scalp for cutaneious/sensory supply?
Cutaneous/sensory innervation is supplied via CN V (V1, V2, V3) & cervical nerves from C2 & C3
CN V1
- Supraorbital N
- Supratrochlear N
CN V2
-Zygomaticotemporal N
CN V3
-Auriculotemporal N
C2
- Greater occipital N
- Lesser occipital N
C3
-Third occipital N
C2 and C3
-Great auricular N
Skin over angle of mandible is not supplied by CN V, but by the cervical plexus with the ___________
Great auricular nerve (C2 and C3)
Innervation fo the auricle and external acoustic meatus?
Superficial cutaneous innervation from lesser occipital (C2), great auricular (C2 and C3) and auriculotemproal (CN V3)
Deep cutaneous by CN VII & CN X
Motor innervation of surrounding muscles by CN VII
What is Ramsay Hunt Syndrome?
Varicella zoster virus reactivation in the geniculate ganglion (CN VII) Leads to: -Otalgia & acute facial palsy Erythematous, vesicular rash in & around the external auditory canal
What is shingles?
Reactivation of varicella zoster virus
Which trigeminal division is involved when there is Reactivation of varicella zoster virus?
Shingles CN V1
What is hutchinson’s sign?
Risk?
cutaneous involvement of the tip of the nose (external nasal branch of nasociliary nerve) in trigeminal shingles.
Risk: Increases likelihood of ocular complications due to interactions of the nasociliary nerve.
Complications: Conjunctivitis, ketatitis (cornea) and uveitis (anterior chamber of globe)
Describe the blood supply to the scalp
Anteriorly: From both internal carotids. Branches are:
- supraorbital
- supratrochlear
Posterior and lateral: Both external carotids. Branches are:
- Superficial temporal
- Posterior auricular
- Occipital
Venous drainage of the scalp?
Veins run alongside the arteries & have the same names draining to the external jugular vein with the exception of the occipital vein that drains to the internal jugular vein
Note arteries are….
Anteriorly: From both internal carotids. Branches are:
- supraorbital
- supratrochlear
Posterior and lateral: Both external carotids. Branches are:
- Superficial temporal
- Posterior auricular
- Occipital
Posterior and anterior lymph drainage of the scalp?
Posterior: Mastoid & occipital nodes —> to deep cervical nodes
Anterior: Pre-auricular & parotid nodes
Muscles of mastication are all derivates of the…
1st pharyngeal arch
Muscles of mastication are?
Temporalis Masseter Medial pterygoid Lateral pterygoid
All muscles of masticationa re innervated by?
All innervated by the motor root of CN V that emerges with CN V3 (anterior trunk except medial pterygoid that comes from the main trunk)
Muscles supplied by CN V3 that AREN’T muscles of mastication?
- Tensor tympani muscle: In middle ear
- Tensor palati (via nerve branch to medial pterygoid)
- Mylohyoid
- Anterior belly of digastric
(via inferior alveolar branch)
Attachements and actions of temporalis?
+ Innervation
Originates from temporal fossa & fascia (broad)
Inserts at coronoid process of mandible (medial surface) & anterior border of ramus
of mandible near last molar (narrow)
Has distinctive fan shape covering temporal fossa
Its actions are to retract & elevate the mandible (i.e. assists in closing the mouth)
Innervated by deep temporal nerves from anterior trunk of CN V3
Masseter: Attachment? Palpation? Action? Innervation?
Originates from inferior border of zygomatic arch (deep head) & maxillary process of zygomatic bone (superficial head)
Inserts at the angle & lateral surface of ramus of mandible
Palpable when teeth are clenched
Its action is to elevate the mandible (powerful elevator)
Innervated by masseteric nerve from anterior trunk of CN V3
Note: There is a deep & a superficial head to this muscle
Medial pterygoid muscle: Divisions? Innervation? Attachment? Actions?
There is a DEEP & a SUPERFICIAL head to this muscle
Innervated by nerve to medial pterygoid from MAIN trunk of CN V3
Originates at medial surface of lateral plate of pterygoid process & pyramidal process of palantine bone (deep head) & tuberosity of pyramidal process of maxilla (superficial head)
Inserts into medial surface of mandible near the angle inferior to mandibular foramen
Its actions are to elevate the mandible & assist with lateral (side-to-side) movements
Lateral pterygoid muscle: Divisions? Innervation? Attachment? Actions?
There is an UPPER & a LOWER head to this muscle
Innervated by nerve to lateral pterygoid from anterior trunk or buccal nerve of CN V3
Originates at roof of infratemporal fossa & crest of wing of sphenoid bone (upper head) & lateral surface of lateral plate of pterygoid process (lower head)
Inserts at condylar process of mandible (pterygoid fovea), capsule of TMJ & articular disc
Its actions are to protrude the mandible, assist medial pterygoid with lateral (side-to-side) movements & depress the mandible
Muscles of mastication responsible for depression?
Gravity Digastric Geniohyoid Mylohyoid Lateral pterygoid
Muscles of mastication responsible for elevation?
Massater
Temporalis
Medial pterygoid
Muscles of mastication responsible for retraction?
Posterior fibres of temporalis
Deep part of masseter
Geniohyoid
Digastric
Muscles of mastication responsible for protrusion?
Lateral pterygoid assisted by medial pterygoid
Gliding movements between _____ bone & articular disc (_____ cavity)
Gliding movements between temporal bone & articular disc (superior cavity)
Hinge & rotational movements between head of mandible & _______ disc (_______ cavity)
Hinge & rotational movements between head of mandible & articular disc (inferior cavity)
What are the muscles of facial expression?
Buccinator Orbicularis oris Orbicular oculi Occipitofrontalis Platysma
Note: All 2nd pharyngeal arch derivatives
Which nerve innervates all the muscles of facial expression?
CN VII
Describe the journey of the CN VII from the brainstem to the parotid gland?
- Enters the skull via the internal acoustic meastus
- Exits via the stylomastoid foramen
- 2 branches are given off posteriorly: Posterior auricular and digastric nerve
- Main nerve enters the parotid gland
- 5 terminal branches arise from a plexus within the gland
What nerve supplies the occipital belly of occipitofrontalis (occipitalis) & auricular muscles?
The posterior auricular which is a branch of the CN VII just after it exits the skull via the stylomastoid foramen
What are the 5 terminal branches of the CN VII?
Temporal N (to frontal belly of occipitofrontalis (frontalis) & orbicularis oculi) Zygomatic N (to orbicularis oculi & upper lip muscles) Buccal N (to buccinator (‘cheek muscle’) & orbicularis oris) Marginal mandibular N (to orbitcularis oris) Cervical N (to platysma)
Buccinator: Muscle of.... Attachments? Actions? Innervation?
Muscle of facial expression
Originates from posterior part of alveolar processes of maxilla/mandible & from pterygomandibular raphe
Fibres merge with orbicularis oris (insertion)
Its actions are to press the cheeks against the molar teeth & works with the tongue
to keep food between occlusal surfaces of teeth & out of the oral vestibule
It also assists with smiling….
Innervated by buccal branches of CN VII
Relationship between buccinator and parotid duct?
Note that the parotid duct lies on top of the masseter before reaching the buccinator & piercing it while en route to the oral cavity where it enters near the superior 2nd molar tooth
Relationship of buccal fat pad and buccinator? Role in infants?
The buccal fat pad lies superficially to the buccinator & is also pierced by the parotid duct
This is much larger in infants to reinforce cheeks & inhibit cheek collapse during feeding
Orbicularis oris:
Innervation?
Attachment?
Actions?
Innervated by buccal & marginal mandibular branches of CN VII
Inserts into mucous membrane of lips
Its actions are to close &/or protrude the lips
Together with the buccinator & tongue, keeps food between occlusal surfaces of teeth
Also assists in whistling…
Platysma:
Attachment?
Innervations?
Actions?
Originates from subcutaneous tissue of the infra & supraclavicular regions
Inserts at base of mandible to merge with orbicularis oris, skin of cheek & lower lip,
angle of mouth & lower lip
Innervation by cervical branch of CN VII
Action: tense the skin of inf face/neck and depress the mandible
Occipitofrontalis:
Innervation?
Attachments?
Actions?
Innervation:
- Temporal branch of CN VII to frontal belly
- Posterior auricular branch of CN VII to the occipital belly
Attachment:
Frontal belly originates from epicranial aponeurosis & inserts into the skin/ subcutaneous tissue of eyebrows & forehead
Occipital belly originates from the lateral 2/3 of superior nuchal line & inserts into the epicranial aponeurosis
Actions:
- Retract the scalp ( by occipital belly)
- Wrinke the forehead and elevate the eyebrows (by frontal belly)
Orbicularis oculi:
Innervation?
Parts of muscle and role?
Origins?
Innervated by temporal & zygomatic branches of CN VII
Palpebral part:
- Originates from the medial palpebral ligament and inserts into the lateral palpebral raphe at the ligament
- Role is to gently closing eyes in involuntary/blinking reflex
Orbital part:
- Originates from the nasal part of the frontal bone, frontal process of maxilla and medial palplebral ligament and inserts into skin around margin of orbit
- Role is to tightly close the eyelids which is a voluntery movement
Which muscles of facial expression are ‘dilators’?
Via insertion to angle of mouth: Levator anguli oris Depressor anguli oris Risorius Zygomaticus major
Via insertion into upper and lower lips:
Levator labii superioris
Depressor labii inferioris
Zygomaticus minor
Which muscles wrinkle skin over dorsum of nose?
Depressor depti
Nasalis
Muscles of facial expression that relate to the ear: Innervation? Which muscles? Arterial supply + venous drainage? Lymph drainage?
Innervate by CN VII
Muscles: Superior auricular, anterior auricular, posterior auricular
Arterial supply is via external carotid artery & venous drainage to external jugular vein as shown for scalp
Lymphatic drainage (like scalp) is via parotid, mastoid & deep cervical nodes
Layers of the eyelid?
Skin Connective tissue Muscle (orbicularis oculi) Orbital septum Tarsus: Superior and inferior muscles give eyelid support Conjunctiva
What is preseptal cellulitis?
Infection of the skin/subcutaneous tissue
(superficial layers) anterior to the orbital septum
Important to differentiate from orbital cellulitis
What is orbital cellulitis?
Infection posterior to the orbital septum
Pain on movements of the eye that are restricted
along with proptosis (bulging of the eye)
Threatens vision & there is risk of infection spread to cavernous sinus or meninges/brain
What is conjunctivitis?
Conjunctivitis (i.e. pink eye)
= Inflammation of the membrane covering the posterior surface of the eyelid & eyeball
Innervation of eyelid?
CN V1 and V2
Arterial supply and venous drainage of eyelid?
Arterial supply is via the external carotid (facial, transverse facial, superficial temporal) & internal carotid (supratrochlear, supraorbital, lacrimal) arteries
Venous drainage is via veins following arteries
Lymphatic drainage of eyelid?
Via parotid nodes
Branches of internal and external carotid that supply the face?
Internal carotid, branches of ophthalamic:
- Zygomatiofacial
- Zygomaticotemporal
- **External carotid:
- Facial
- BUccal, mental, infraorbital (branches of the maxillary)
- Transverse facial (branch of the sup temporal_
Venous drainage of face?
Facial vein drains most of the face to internal jugular vein Transverse facial vein drains some of the upper face
What is the danger triangle of the face?
No valves in the external facial veins Blood flows in both directions Veins deep to danger triangle drain to cavernous sinus Skin infections in this area may spread as intracranial infections
Lymph drainage of the face?
- Pre-auricular & Parotid: Near ear, from eyelids,
lateral cheek, external nose - Submandibular: Follows facial artery, from medial orbit, external nose, medial cheek, upper lip, lateral lower lip
- Submental: Inferior chin, from medial lower lip & chin
