Head and Neck Overview

Scalp: soft tissue covering the calvaria.

• Face: anterior soft tissue region overlying the viscerocranium.
• Cranial cavity: houses the brain and its coverings.
• Orbit: paired bony cavities containing the eyes and associated structures.
• Nasal cavity and paranasal sinuses: airway/olfactory structures.
• Oral cavity: mouth, tongue, teeth, palate.
• Pharynx: shared airway/food passage, subdivided into naso-, oro-, and laryngopharynx.
• Larynx: airway/phonation organ.
• Neck: connects head to thorax, containing the cervical viscera, major vessels, nerves, and muscular triangles.

• Five-layered soft tissue covering the skull vault (skin, dense connective tissue, epicranial aponeurosis, loose areolar tissue, pericranium, mnemonic SCALP).

• Anterior soft tissue overlying the facial skeleton, containing the muscles of facial expression (facial nerve-innervated) and sensory supply from the trigeminal nerve's three divisions.

• Contained within the neurocranium, divided internally into the anterior, middle, and posterior cranial fossae, each housing corresponding parts of the brain; full detail in Section 2.

• Paired pyramidal bony cavities housing the eyeballs, extraocular muscles, lacrimal apparatus, and the neurovascular structures supplying them.

• Paired cavities divided by the nasal septum, each with a roof, floor, and lateral wall bearing the three conchae; connects to the paranasal sinuses and nasopharynx; full detail in Section 9.

• Bounded by the lips, cheeks, palate (roof), and floor of mouth, containing the tongue and teeth, continuous posteriorly with the oropharynx.

• A muscular tube extending from the skull base to the oesophagus, subdivided into nasopharynx (behind the nose, above the soft palate), oropharynx (behind the mouth, soft palate to epiglottis), and laryngopharynx (behind the larynx, epiglottis to the cricoid cartilage/oesophageal junction).

• The airway/phonation organ, suspended from the hyoid bone, continuous with the trachea below; full detail in Section 12.

• Extends from the skull base/mandible to the thoracic inlet, organised into anterior and posterior triangles by sternocleidomastoid, containing the cervical viscera (thyroid, parathyroids, trachea, oesophagus), major vessels (carotid sheath contents), and cervical fascial layers; full detail in Sections 4, 13.

• Thyroid and parathyroid glands, trachea, cervical oesophagus, larynx: the visceral column running through the anterior neck, enclosed by the pretracheal fascia; full detail in Sections 12-13.

• Superficial cervical fascia (contains platysma), investing layer of deep cervical fascia (encircles the neck, splitting around sternocleidomastoid and trapezius), pretracheal fascia (encloses the visceral column), prevertebral fascia (covers the vertebral column and its muscles), and the carotid sheath (a condensation enclosing the common/internal carotid artery, internal jugular vein, and vagus nerve).

• Arterial: Common carotid arteries (bifurcating into external and internal carotid arteries), vertebral arteries, subclavian arteries.
• Venous: Internal jugular vein (the dominant venous drainage), external jugular vein, and their tributaries.

• Twelve cranial nerves (CN I-XII): the dominant nervous supply to the head and neck.
• Cervical plexus (C1-C4): supplies neck skin and some neck muscles, and contributes to the phrenic nerve.
• Cervical sympathetic trunk.

• Extensive network of named node groups (submental, submandibular, parotid, occipital, mastoid, superficial and deep cervical) converging on the deep cervical nodes, draining into the jugular lymphatic trunks.

• Supraorbital margin, zygomatic arch, mandible, mastoid process, hyoid bone, thyroid and cricoid cartilages, trachea, sternocleidomastoid, carotid pulse.

• Neurocranium: The bones enclosing and protecting the brain (frontal, parietal (paired), temporal (paired), occipital, sphenoid, ethmoid) forming the cranial vault (calvaria) and base.
• Viscerocranium (facial skeleton): The bones forming the face, maxilla (paired), zygomatic (paired), nasal (paired), lacrimal (paired), palatine (paired), inferior nasal conchae (paired), vomer, mandible.
• This division is a foundational organising principle for Section 2's detailed osteology.

• Anterior triangle (bounded by the midline, mandible, and sternocleidomastoid), subdivided into submental, submandibular, carotid, and muscular triangles.
• Posterior triangle (bounded by sternocleidomastoid, trapezius, and the clavicle), subdivided into occipital and omoclavicular (subclavian) triangles.
• Full detail in Section 4.

• Twelve paired cranial nerves, numbered I-XII by their order of attachment to the brain (rostral to caudal), each with a specific combination of functional components (motor, sensory, special sensory, parasympathetic), some purely sensory (I, II, VIII), some purely motor (IV, VI, XI, XII), and several mixed (III, V, VII, IX, X).

• Common carotid artery → external carotid artery (supplies the face, scalp, and most extracranial head/neck structures) and internal carotid artery (supplies the brain and orbit, via the ophthalmic artery), the fundamental arterial branching pattern of the head and neck.
• Subclavian artery → vertebral artery (supplies the posterior brain circulation, via the basilar artery), a second major arterial contribution to intracranial supply, distinct from the carotid system.

• Internal jugular vein: the dominant venous drainage of the head and neck, receiving the facial, lingual, and superior/middle thyroid veins among others, running within the carotid sheath.
• External jugular vein: drains the scalp and superficial face, a more superficial, less consistently sized vessel.
• Both drain into the subclavian vein, joining to form the brachiocephalic vein.

• Retropharyngeal space, danger space, prevertebral space: potential fascial planes of major clinical significance for the spread of deep neck infection, full detail in Section 4.
• Infratemporal and pterygopalatine fossae: deep facial spaces, full detail in Section 14.