Download Anatomy Lecture 3- Face and Scalp

Anatomy Lecture 3: Face and Scalp
Concentration on CN V (Trigeminal): V3 Branch (Mandibular) and CN VII (Facial)
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Cortico-Bulbar Pathway (Facial Nerve CN VII)
o Facial Nerve Branches
 Temporal
 Zygomatic
 Buccal
 Mandibular
 Cervical
o All Facial Nerve Branches pass through the Parotid Gland
o They can overlap in each other’s regions
o Pathway:
 Upper Motor Neurons: Facial Region of Motor Homunculus
 Lower Motor Neurons: Facial Motor Nucleus in the brainstem
on the opposite side.
Bell’s Palsy
o Paralysis of the Facial Nerve (peripheral branches)
 Due to LMN Lesion
o Indeterminate cause (Lyme disease is implicated)
o Usually lasts 3-5 days
o Muscles Affected?
 Orbicularis Oris: drooling
 Buccinator: disrupted swallowing/speech
 Orbicularis Oculi: tears cannot wet eyeball  ulceration
o Can sometimes be remedied by end-to-end nerve anastomosis.
Lesions of the Facial Nerve:
o Small Branch: Innervates stapedius muscle, which dampens sound.
o Large Branch: Exits skull via Stylomastoid Foramen. Innervates:
 Stylohyoid Muscle
 Posterior Belly of Digastric Muscle
 Then, it branches to form the branches on the face:
o Temporal
o Zygomatic
o Buccal
o Mandibular
o Cervical
o Lesions:
 Stylomastoid Foramen: Bell’s Palsy
 Facial Canal: Bell’s Palsy and Hyperacusis (exaggerated sound)
 Internal Auditory Meatus: Bell’s Palsy, Hyperacusis, and
Problems with Hearing and Balance
 Can also include:
o Reduced Tearing and Salivation (Lacrimal,
Submandibular, and Sublingual Glands)
o Taste
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The Parotid Gland
o 1 of 3 Salivary Glands
o Parotid Duct: Stenson’s Duct
 Crosses the face, wraps medial to the Masseter Muscle 
Pierces the Buccinators Muscle  Enters the mouth adjacent
to the 2nd Maxillary Molar Tooth
o Common Problems:
 Parotitis (Mumps)
 High contagious viral infection
 Controlled by vaccinations
 Symptoms: Swelling and Pain
 Common in:
o Youth
o Adults:
 Can cause swelling of testicles and
infertility.
 Pleomorphic Adenomas:
 Benign Tumors
o The branches of VII (Facial Nerve) go through the parotid gland in one
plane, so that the gland above and below can be removed without
damaging the nerve.
Parasympathetic Innervation of the Parotid Gland: CN IX
o Pre-Ganglionic Parasympathetic Neurons: Inferior Salivary Nucleus
o Exit: CN IX (Glossopharyngeal):
o Post-Ganglionic Parasympathetic Neurons: Otic Ganglion
o Then, the axons enter the auriculo-temporal branch of V3 to the gland.
o Frey’s Syndrome:
 When the Parotid Gland is removed, parasympathetic nerves
are severed. These axons regenerate and innervate sweat
glands.
 When the parasympathetic system is activated by eating, the
sweat glands are activated.
Muscles of Mastication: CN X, V3 (Mandibular Branch)
o LMN’s of V3 activate the Muscles of Mastication:
 Masseter
 Temporalis
 Medial and Lateral Pterygoids
o Pathway:
 Upper Motor Neurons
 Lower Motor Neurons: Motor Nucleus of V
o Axons of LMN produce a coordinated activation of muscles resulting
in mastication.
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Trigeminal Neuralgia:
o Tic Doloroux
o Horrendous, debilitating pain that usually involves infraorbitcal
nerve.
o There is no known spinal counterpart
Circulation of the Orofacial Region
o Arteries:
 Carotid
 Internal Carotid  No external branches (supplies
brain)
 External Carotid  Supplies oro-facial region
o Facial Branch – convolutes around the mouth to
avoid stretching
o Superior Temporal Branch – supply the scalp
 These can bleed copiously because they
are not end arteries.
o Veins:
 Facial Vein: Lower boarder of the mandible
 Receives tributaries from lips, palpebral, and external
nasal areas.
 Becomes the Common Facial Vein
 Joins the Retromandibular Vein.
 Terminates in the Internal Jugular Vein
 DOES NOT HAVE VALVES
The Facial Skull:
o Most Common Fractures:
 Nasal Bone: readily repaired
 Mandible: Across foramina
 Can be accompanied by a fracture on the contralateral
side
 Repair is challenging
 3D MRI’s are the best to diagnose skull fractures
o Le Fort Fractures
 Type I: Horizontal Across Maxillae
 Type II: Maxillary Sinuses, infraorbital foramina, bones of
medial orbit, across bridge of nose
 The entire central part of the face becomes separated
from the skull.
 Type III: Horizontal through Superior Orbital Fissure.
 Causes separation from the skull.
 Types II and III are the most serious because they involve the
orbit.
 Crouzon’s Syndrome:
 Pre-mature closure of facial sutures results in a
flattened face. This can be corrected by moving the
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central region of the face forward after disarticulation
following the LeFort II fracture lines.
The Scalp
o Considerable protection to the skull
o Consists of 5 layers:
 Skin
 Connective Tissue
 Dense and contains the extensive network of superficial
blood vessels and nerves.
 The arteries from each side anastomose so that a blow
to the head can result in excessive bleeding.
 It is possible to move the skin and blood vessels from
the scalp onto the face for plastic surgery
 The superficial veins interconnect with those within the
skull and can carry infection to the meninges.
 Aponeurosis (galea aponeurotica)
 Of the Temporalis, Frontalis, and Occipitalis Muscles
 Firm and difficult to penetrate
 Loose Connective Tissue:
 Forms a potential space under the galea aponeurotica
that is easily filled with blood. This is the danger area of
the scalp and blood can extravasate into the peri-orbital
region resulting in ecchymosis (raccoon eyes)
 Periostem of the Skull:
 The rich blood supply of the scalp facilitates its use as a
source of skin for facial reconstruction.