Head & Neck
Skull, face, orbit, ear, oral and nasal cavities, pharynx, larynx, and the triangles of the neck.
31 entriesSkull: 4Face & scalp: 4Orbit: 3Ear: 2Oral & nasal cavities: 4Pharynx & larynx: 4Neck: 10
Bones (2)
- Mandible The lower jaw — the largest facial bone and the only movable bone of the skull. As a ring with the skull base, it often fractures in two places, and the inferior alveolar nerve runs through it.
- Skull HYThe bones of the head — the neurocranium enclosing the brain and the viscerocranium forming the face. Pterion fractures, basilar skull fractures and infant fontanelles are the clinically important features.
Muscles (4)
- Extraocular muscles HYSix muscles that move each eye — four recti and two obliques — supplied by CN III, IV and VI (LR6 SO4, the rest 3). Testing them in the "H" pattern localizes cranial nerve palsies.
- Muscles of facial expression HYThin subcutaneous muscles derived from the second pharyngeal arch and supplied by the facial nerve (CN VII). Their pattern of weakness distinguishes a peripheral facial palsy (Bell palsy) from a stroke.
- Muscles of mastication HYFour muscles derived from the first pharyngeal arch and supplied by the mandibular nerve (V3) — masseter, temporalis and medial pterygoid close the jaw; lateral pterygoid opens and protrudes it.
- Sternocleidomastoid HYProminent two-headed neck muscle that divides the neck into anterior and posterior triangles. It is supplied by the accessory nerve and is shortened in congenital muscular torticollis.
Nerves (2)
- Cervical plexus HYNetwork of the C1–C4 ventral rami deep to sternocleidomastoid. It gives cutaneous branches to the neck and ear, the ansa cervicalis to the strap muscles, and most importantly the phrenic nerve (C3–C5) to the diaphragm.
- Recurrent laryngeal nerve HYBranch of the vagus that loops under the subclavian artery on the right and the aortic arch on the left, then climbs in the tracheoesophageal groove to supply the larynx. Injury causes hoarseness, a classic thyroidectomy complication.
Arteries (3)
- Common and internal carotid arteries HYMain arteries of the head. Each common carotid divides at about C4 into external and internal carotids, and atherosclerosis at the bifurcation is a major cause of stroke and TIA.
- External carotid artery HYMain artery of the face, scalp and neck outside the skull. It has eight branches (SALFOPSM) and ends in the parotid gland as the superficial temporal and maxillary arteries.
- Middle meningeal artery HYBranch of the maxillary artery that enters the skull through the foramen spinosum to supply the dura and skull. Tearing of its anterior branch under the pterion causes an epidural hematoma.
Veins (1)
Lymphatics (2)
- Cervical lymph nodes HYSuperficial and deep nodes of the head and neck, grouped clinically into levels I–VI. Lymphadenopathy is common, and a persistent neck mass in an adult is cancer until proven otherwise.
- Palatine tonsils HYPaired masses of lymphoid tissue in the tonsillar fossae of the oropharynx, part of Waldeyer ring. Streptococcal pharyngitis, peritonsillar abscess and infectious mononucleosis are the key problems.
Organs (11)
- External and middle ear HYThe ear canal, eardrum and air-filled tympanic cavity with its three ossicles, connected to the nasopharynx by the pharyngotympanic tube. Otitis externa, otitis media and conductive hearing loss are the key topics.
- Eyeball HYThe globe of the eye — three coats (fibrous, vascular, neural) around the lens and chambers. Acute angle-closure glaucoma, retinal detachment, central retinal artery occlusion and the red eye are its emergencies.
- Inner ear HYFluid-filled bony and membranous labyrinth in the petrous temporal bone — the cochlea for hearing and the vestibule and semicircular canals for balance. Sensorineural hearing loss and peripheral vertigo arise here.
- Larynx HYCartilaginous airway organ from C3 to C6 that protects the airway and produces voice. Epiglottitis, croup, vocal cord paralysis from recurrent laryngeal nerve injury and emergency cricothyrotomy are the key topics.
- Parathyroid glands HYUsually four small endocrine glands on the back of the thyroid that secrete parathyroid hormone. They are important in hypercalcemia (primary hyperparathyroidism) and in hypocalcemia after thyroid surgery.
- Parotid gland HYThe largest salivary gland, in front of the ear, with the facial nerve branching through it. Mumps, bacterial parotitis, stones and tumors (most often pleomorphic adenoma) are its key problems.
- Pharynx Fibromuscular tube from the skull base to C6, shared by the airway and the food passage. It is divided into nasopharynx, oropharynx and laryngopharynx, and the site of Zenker diverticulum and nasopharyngeal carcinoma.
- Scalp Five-layered soft tissue covering the skull vault. Its rich blood supply makes lacerations bleed heavily, and its loose areolar "danger layer" lets infection spread into the skull.
- Submandibular gland Salivary gland under the body of the mandible that produces most resting saliva. It is the most common site of salivary stones because its duct runs uphill and its saliva is thick.
- Thyroid gland HYButterfly-shaped endocrine gland wrapped around the upper trachea at C5–T1. It moves with swallowing, lies next to the recurrent laryngeal nerves and parathyroids, and thyroid nodules are a common workup.
- Tongue HYMuscular organ of taste, speech and swallowing. Its mixed embryologic origin gives it four different nerve supplies, and hypoglossal lesions make it deviate toward the weak side.
Joints (1)
Spaces & regions (5)
- Deep neck spaces HYPotential spaces between the layers of deep cervical fascia. Infections can track through them from the teeth, tonsils and pharynx into the mediastinum.
- Nasal cavity HYPaired air passages from the nostrils to the choanae, divided by the septum and lined by the conchae that warm and humidify air. Anterior epistaxis from Kiesselbach plexus is the classic problem.
- Orbit HYPyramidal bony cavity holding the eyeball, extraocular muscles, nerves and vessels. Its thin floor and medial wall break in blowout fractures, and infection behind the orbital septum is an emergency.
- Paranasal sinuses HYFour paired air-filled cavities — frontal, ethmoid, sphenoid and maxillary — draining into the nasal cavity. Acute sinusitis is usually viral; ethmoid and frontal infections can spread to the orbit and brain.
- Triangles of the neck HYSternocleidomastoid divides each side of the neck into anterior and posterior triangles, and each is subdivided further. Knowing their contents helps localize neck masses and avoid injuring the accessory nerve.