Session 2: The Facial Skeleton, Scalp and Face; The Orbit and Associated Cranial Nerves Flashcards
What 5 layers does the scalp consist of?
S - skin C - connective tissue A - aponeurosis L - loose connective tissue P - periosteum
Why is the superficial connective tissue layer of the scalp unique?
It is fibrous and tightly bound both to skin and underlying aponeurosis, so there is no movement between the two.
How is sliding of the scalp over the cranium possible?
Because of the layer of loose areolar connective tissue between the aponeurosis and the periosteum.
What is the layer of loose areolar connective tissue between the aponeurosis and periosteum of the scalp known as?
The subaponeurotic fascia.
Why do scalp wounds tend to bleed profusely and require suturing?
Because the dense fibrous tissue tends to hold the walls of superficial blood vessels open even when they are cut.
Why does a transverse tear to the aponeurosis cause gaping?
Due to the pull of occipitalis and frontalis muscles across the defect
Which is easier to suture, a transverse or sagittal tear in the aponeurosis?
A sagittal tear, because no gaping.
Why are wounds that penetrate the aponeurosis serious?
As infection can enter the subaponeurotic space and spread over the entire surface of the cranial vault with little obstruction.
Which blood vessels supply the scalp?
From ICA: - supratrochlear (opthalmic) - supraorbital (opthalmic) From ECA: - superficial temporal - posterior auricular - occipital
All these vessels anastomose freely with eachother
What is the nerve supply of the posterior scalp?
Greater occipital nerve (posterior rami C2)
Third occipital nerve (posterior rami C3)
What is the nerve supply of the lateral scalp?
Lesser occipital nerve (C2) Auriculotemporal nerve (Vc)
What is the nerve supply of the scalp anteriorly and up to the vertex?
Zygomaticotemporal nerve (Vb) Supraorbital neve (Va) Supratrochlear nerve (Va)
The facial nerve gives branchiomotor supply to all the muscles from which pharyngeal arch?
2nd pharnygeal arch
Which glands does the facial nerve carry preganglionic parasympathetic fibres for? (4)
Lacrimal
Submandibular
Sublingual
Nasal mucous
What does the facial nerve carry taste fibres from (via the chorda tympani branch)?
Anterior 2/3 tongue
What part of the head does the facial nerve supply general sensation to?
The skin lining the external auditory meatus
What are the 2 roots of the facial nerve?
The larger motor root and the smaller nervus intermedius (carrying sensory and parasympathetic).
Describe the course of the facial nerve (from the IAM to the stylomastoid foramen).
The two roots enter the internal acoustic foramen with the vestibulocochlear nerve (VIII), and join to form the facial nerve.
The facial nerve then enters the facial canal in the petrous temporal bone.
On the medial wall of the middle ear, the facial nerve bends posteriorly, and gives off the greater petrosal nerve at the geniculate ganglion.
On reaching the posterior wall of the tympanic cavity, the nerve runs inferiorly to emerge from the skull at the stylomastoid foramen.
What does the facial nerve do upon exiting the stylomastoid foramen?
It enters the parotid gland and divides into upper and lower divisions.
Which nerves does the upper division of the facial nerve give?
Temporal
Zygomatic
Buccal
Which nerves does the lower division of the facial nerve give?
Mandibular
Cervical
Which branches does the facial nerve give before exiting the skull through the stylomastoid foramen? (3)
Greater petrosal nerve
Nerve to stapedius
Chorda tympani
Where does the greater petrosal nerve arise?
Geniculate ganglion
What does the greater petrosal nerve carry?
Parasympathetic preganglionic fibres to the pterygopalatine ganglion.
What is the action of stapedius? What is its nerve supply?
Dampens over-vibration of the tympanic membrane and ossicles. Nerve to stapedius (VII).
Which nerve does the chorda tympani join?
Lingual nerve (Vc)
What does the chorda tympani supply?
Taste to anterior 2/3 tongue
Preganglionic parasympathetic to submandibular ganglion.
Which muscular branches of the facial nerve are given off after exiting the skull? (NOT to muscles of facial expression)
Posterior belly of digastric
Stylohyoid
Occipitalis
What does the temporal nerve (VII) supply?
Orbicularis oculi
Frontalis
What does the zygomatic nerve (VII) supply?
Muscles of the eyelid
What does the buccal nerve (VII) supply?
Buccinator
Orbicularis oris
Levator oris
What does the mandibular nerve (VII) supply?
Depressor oris
Muscles of the lower lip and chin
What does the cervical nerve (VII) supply?
Platysma
What shape is the orbit? Where does the apex point?
Cone-shaped; posteromedially.
Which walls of the orbit are almost parallel to each other?
Medial walls
Which walls of the orbit are at right angles to each other?
Lateral walls
What forms the roof of the orbit? What does it separate the orbit from?
Orbital plate of frontal bone; frontal lobe of brain.
What forms the floor of the orbit?
The maxilla with its air sinus.
What forms the lateral wall of the orbit? What does it separate the orbit from?
Zygomatic bone and greater wing of sphenoid; the temporalis muscle.