Head & Neck Anatomy Notes

The Face

• External Appearance & Human Variation
  • Skull shape
  • Muscle and soft tissue
  • Buccal fat pad
  • Highly vascularized
  • Sebaceous glands

Muscles of the Scalp & Face

• Muscles of facial expression develop from the mesoderm of the 2nd pharyngeal arch
• All facial muscles are innervated by the Facial Nerve (CNVII)

Muscles of Facial Expression

• Occipitofrontalis
  • Frontal belly
    • Origin: Epicranial aponeurosis
    • Insertion: Skin and subcutaneous tissue of eyebrows and forehead
    • Action: Elevates eyebrows and wrinkles skin of forehead; protracts scalp (indicating surprise or curiosity)
  • Occipital belly
    • Origin: Lateral two thirds of superior nuchal line
    • Insertion: Epicranial aponeurosis
    • Action: Retracts scalp; increasing effectiveness of frontal belly
• Orbicularis oculi (orbital sphincter)
  • Origin: Medial orbital margin; medial palpebral ligament; lacrimal bone
  • Insertion: Skin around margin of orbit; superior and inferior tarsal plates
  • Action: Closes eyelids: palpebral part does so gently; orbital part tightly (winking)
• Corrugator supercilii
  • Origin: Medial end of superciliary arch
  • Insertion: Skin superior to middle of supra-orbital margin and superciliary arch
  • Action: Draws eyebrow medially and inferiorly, creating vertical wrinkles above nose (demonstrating concern or worry)
• Procerus plus transverse part of Nasalis
  • Origin: Fascia aponeurosis covering nasal bone and lateral nasal cartilage
  • Insertion: Skin of inferior forehead, between eyebrows
  • Action: Depresses medial end of eyebrow; wrinkles skin over dorsum of nose (conveying disdain or dislike)
• Alar part of nasalis plus Levator labii superioris alaeque nasi
  • Origin: Frontal process of maxilla (inferomedial margin of orbit)
  • Insertion: Major alar cartilage; lateral part of skin of upper lip
  • Action: Depresses ala laterally, dilating anterior nasal aperture (i.e., "flaring nostrils," as during anger or exertion); helps to elevate upper lip
• Orbicularis oris (oral sphincter)
  • Origin: Medial maxilla and mandible; deep surface of peri-oral skin; angle of mouth (modiolus)
  • Insertion: Mucous membrane of lips
  • Action: Tonus closes oral fissure; phasic contraction compresses and protrudes lips (kissing) or resists distension (when blowing)
• Levator labii superioris
  • Origin: Infra-orbital margin (maxilla)
  • Insertion: Skin of upper lip
  • Action: Part of dilators of mouth; retract (elevate) and/or evert upper lip; deepen nasolabial sulcus (showing sadness)
• Zygomaticus minor
  • Origin: Anterior aspect, zygomatic bone
  • Insertion: Skin of upper lip
• Buccinator (cheek muscle)
  • Origin: Mandible, alveolar process of maxilla and alveolar part of mandible, pterygomandibular raphe
  • Insertion: Angle of mouth (modiolus); orbicularis oris
  • Action: Presses cheek against molar teeth; works with tongue to keep food between occlusal surfaces and out of oral vestibule; resists distension (when blowing)
• Zygomaticus major
  • Origin: Lateral aspect of zygomatic bone
  • Insertion: Angle of mouth (modiolus)
  • Action: Part of dilators of mouth; elevate labial commissure—bilaterally to smile (happiness); unilaterally to sneer (disdain)
• Levator anguli oris
  • Origin: Infra-orbital maxilla (canine fossa)
  • Insertion: Angle of mouth (modiolus)
• Risorius
  • Origin: Parotid fascia and buccal skin (highly variable)
  • Insertion: Angle of mouth (modiolus)
  • Action: Part of dilators of mouth; widens oral fissure, as when grinning or grimacing
• Depressor anguli oris
  • Origin: Anterolateral base of mandible
  • Insertion: Angle of mouth (modiolus)
  • Action: Part of dilators of mouth; depresses labial commissure bilaterally to frown (sadness)
• Depressor labii inferioris
  • Origin: Platysma and anterolateral body of mandible
  • Insertion: Skin of lower lip
  • Action: Part of dilators of mouth; retracts (depresses) and/or everts lower lip (pouting, sadness)
• Mentalis
  • Origin: Body of mandible (anterior to roots of inferior incisors)
  • Insertion: Skin of chin (mentolabial sulcus)
  • Action: Elevates and protrudes lower lip; elevates skin of chin (showing doubt)
• Platysma
  • Origin: Subcutaneous tissue of infraclavicular and supraclavicular regions
  • Insertion: Base of mandible; skin of cheek and lower lip; angle of mouth (modiolus); orbicularis oris
  • Action: Depresses mandible (against resistance); tenses skin of inferior face and neck (conveying tension and stress)
• All facial muscles are innervated by the facial nerve (CN VII) via its posterior auricular branch or via the temporal, zygomatic, buccal, marginal mandibular, or cervical branches of the parotid plexus.

Smiling Muscles

• Levator labii superioris
• Zygomaticus major
• Levator anguli oris
• Risorius
• Orbicularis oculi
  • Palpebral
  • Orbital
  • Lacrimal

Frowning Muscles

• Depressor labii inferioris
• Depressor anguli oris
• Platysma
• Orbicularis oris
• Orbicularis oculi
• Corrugator supercilii
• Procerus
• Mentalis

Other Facial Muscles

• Buccinator
• Nasalis
• Levator labii superioris alaque nasii
• Masseter (innervated by CN V3)

Palpebral and Oral Fissures

• Palpebral fissure (eye)
  • Sphincter: Orbicularis oculi
  • Dilator: Levator palpebrae superioris and occipitofrontalis (anterior portion = frontalis and posterior portion = occipitalis)
• Oral fissure (mouth)
  • Sphincter: Orbicularis oris
  • Dilator: All muscles of oral movement except mentalis

Parotid Region

• Parotid gland
• Parotid duct
• Parotid plexus of CN VII
• Retromandibular vein
• External carotid artery
• Masseter muscle

Salivary Glands

• Parotid glands
• Submandibular glands
• Sublingual glands
• Saliva Functions
  • Maintains moist environment for oral mucosa
  • Lubrication during chewing
  • Digestion and breakdown of starches
  • Prevention of tooth decay/maintenance of biofilm

Parotid Gland

• Largest salivary gland
• Anteroinferior to external acoustic meatus
• Parotid sheath/capsule: Derived from investing layer of deep cervical fascia
• Stylomandibular ligament
• Parotid duct: Runs horizontally with buccal nerve from anterior of gland
  • Pierces buccinator
  • Enters oral cavity opposite the 2nd maxillary molar

Innervation of the Face

Motor Innervation

• Facial nerve (CN VII)
  • Posterior auricular nerve
  • Terminal branches (parotid plexus)
    • Temporal
    • Zygomatic
    • Buccal
    • Marginal mandibular
    • Cervical

Sensory Innervation

• Trigeminal nerve
  • Ophthalmic nerve (V1)
    • Supraorbital nerve
    • Supratrochlear nerve
  • Maxillary nerve (V2)
    • Infraorbital nerve
  • Mandibular nerve (V3) - Sensory AND motor
    • Auriculotemporal nerve
    • Mental nerve
    • Buccal nerve

Parotid Gland Innervation

• CN VII does NOT innervate the parotid gland
• Auriculotemporal nerve (branch of V3)
  • Parasympathetic innervation: CN IX – otic ganglion
  • External carotid plexus: Sympathetic innervation
  • Sensory fibers: Auriculotemporal nerve, Great auricular nerve

Vasculature of the Face

Arterial Supply

• Facial artery: Branch of external carotid artery
  • Facial artery branches:
    • Inferior labial artery
    • Superior labial artery
    • Angular artery
• Superficial temporal artery: Terminal branch of external carotid artery
  • Transverse facial artery

Venous Supply

• Facial vein: Communicates with superior ophthalmic vein (drains into Cavernous Sinus)
• Retromandibular vein: Union of superficial temporal & maxillary veins
  • Divides into anterior and posterior divisions
    • Anterior division + Facial vein = Common Facial Vein (Drains into Internal Jugular Vein)
    • Posterior division + Posterior Auricular Vein = External Jugular Vein

Danger Triangle of the Face

• Facial vein has no valves
• Communication between facial vein and cavernous sinus = potential for spread of infection

Lymphatic Drainage

• Superficial ring (pericervical collar) of lymph nodes
  • Submental
  • Submandibular
  • Parotid
  • Mastoid
  • Occipital
• Superficial lymph vessels follow veins
• Deep lymph vessels follow arteries
• All drain into deep cervical lymph nodes (along Internal Jugular Vein)

Superficial Neck

Cervical Fascia

• Superficial cervical fascia:
  • Cervical subcutaneous tissue
  • Contains the platysma
  • Contains superficial nerves and vessels
• Deep cervical fascia:
  • Support cervical viscera
  • Forms carotid sheath
  • Three layers:
    • Investing
    • Pretracheal
    • Prevertebral
  • Limit infection spread, reduce friction between moving structures & surgical planes

Superficial Neck - Muscles

• Platysma
  • Origin: Fascia overlying pectoralis major and deltoid muscles
  • Insertion: Inferior border of mandible, skin, & subcutaneous tissues of lower face
  • Innervation: CN VII Facial Nerve
  • Actions: Draws corners of mouth inferiorly & widens it (Sadness & fright), Draws skin of neck superiorly when teeth are clenched
• Sternocleidomastoid
  • Origin: Sternal Head: anterior surface of manubrium; Clavicular Head: superior surface of medial third of clavicle
  • Insertion: Lateral surface of mastoid process, temporal Lateral half of superior nuchal line
  • Innervation: CN XI Spinal Accessory Nerve, C3 & C4 pain & proprioception
  • Action
    • Unilateral contraction: tilts head to same side (laterally flexes neck) and rotates it so face is turned superiorly toward opposite side
    • Bilateral contraction:
      • Extends neck at atlanto-occipital joints
      • Flexes cervical vertebrae so that chin approaches manubrium
      • Extends superior cervical vertebrae while flexing inferior vertebrae, so chin is thrust forward with head kept level
    • With cervical vertebrae fixed, may elevate manubrium & medial ends of clavicles, assisting pump-handle action of deep respiration

Triangles of the Neck

• Posterior triangle: Borders: Trapezius, SCM, clavicle
  1. Occipital triangle
  2. Subclavian triangle
• Anterior triangle: Borders: SCM, midline, mandible
  1. Submandibular (digastric) triangle
  2. Submental triangle
  3. Carotid triangle
  4. Muscular triangle

Superficial Neck - Innervation

• Cervical plexus: Ventral rami of C1-C4
  • Cutaneous branches
  • Nerve Point of the Neck (Erb’s Point)
    • Lesser occipital nerve (C2)
    • Great auricular nerve (C2 and C3)
    • Transverse cervical nerve (C2 and C3)
    • Supraclavicular nerves (C3 and C4) (Medial, intermediate, lateral)

Superficial Neck - Blood Supply

• Arteries: May see transverse cervical artery
• Veins:
  • Anterior jugular vein, Submandibular veins. Drains to External jugular or subclavian veins
  • External jugular vein: Posterior division of retromandibular vein, Posterior auricular vein