Head and neck anatomy for FCPS Part 1

Why head and neck matters

Head and neck anatomy is dense, but the questions keep returning to the same structures because they matter in surgery and clinical examination:

• cranial nerves and what their lesions look like
• the parotid gland and facial nerve
• the neck triangles and the carotid sheath
• the thyroid and the nerves near it
• the larynx

Cranial nerves: lesion first

Face and scalp

• The scalp has five layers (skin, connective tissue, aponeurosis, loose areolar tissue, pericranium). The loose areolar layer is the "danger area", where infection can spread to the cranial cavity through emissary veins.
• The "danger triangle" of the face drains through the facial and ophthalmic veins to the cavernous sinus, so infection there can cause cavernous sinus thrombosis.
• Sensation of the face is from the trigeminal nerve (V1, V2, V3). The angle of the jaw is supplied by the great auricular nerve (C2–C3), not the trigeminal.

Parotid gland and facial nerve

• The facial nerve enters the parotid and divides into five branches: temporal, zygomatic, buccal, marginal mandibular and cervical.
• Structures in the gland from superficial to deep: facial nerve, retromandibular vein, external carotid artery.
• Parasympathetic secretomotor fibres to the parotid come from the glossopharyngeal nerve, via the otic ganglion and auriculotemporal nerve. Regrowth of these fibres to sweat glands after parotid surgery causes Frey syndrome (gustatory sweating).

Neck triangles

• Anterior triangle: the carotid sheath holds the common carotid artery (medial), internal jugular vein (lateral) and vagus nerve (between and behind). The carotid bifurcates at the upper border of the thyroid cartilage.
• Posterior triangle: the accessory nerve crosses it superficially. It is the structure most at risk during lymph node biopsy there, causing weakness of trapezius.
• The external jugular vein crosses sternocleidomastoid; the phrenic nerve lies on scalenus anterior.

Thyroid

• Invested in pretracheal fascia, so it moves with swallowing. A thyroglossal cyst moves with tongue protrusion.
• The recurrent laryngeal nerve runs near the inferior thyroid artery. The external laryngeal nerve runs with the superior thyroid artery.
• After thyroidectomy: unilateral recurrent laryngeal injury gives hoarseness; bilateral injury can cause stridor; external laryngeal injury reduces voice pitch. Parathyroid injury gives hypocalcaemia.

Larynx

• All intrinsic muscles are supplied by the recurrent laryngeal nerve, except cricothyroid (external laryngeal nerve).
• Posterior cricoarytenoid is the only muscle that abducts (opens) the vocal cords.
• Sensation above the cords is from the internal laryngeal nerve; below the cords from the recurrent laryngeal.
• The left recurrent laryngeal nerve hooks under the arch of the aorta, so it can be affected by aortic aneurysm, lung cancer or an enlarged left atrium.
• Emergency surgical airway goes through the cricothyroid membrane.

Common traps

• The mandibular nerve (V3) is the only trigeminal division with motor fibres (muscles of mastication).
• Taste from the anterior two-thirds of the tongue travels with the chorda tympani (VII); general sensation with the lingual nerve (V3).
• The internal carotid artery has no branches in the neck. The external carotid does.
• The submandibular duct is crossed by the lingual nerve, which is at risk when removing a duct stone.

How to revise in one week

1. Day 1: cranial nerves, by lesion.
2. Day 2: scalp, face and their venous connections.
3. Day 3: parotid, submandibular glands and the facial nerve.
4. Day 4: neck triangles and the carotid sheath.
5. Day 5: thyroid, parathyroid and their nerves.
6. Days 6 to 7: larynx, pharynx and mixed questions.

Practise these in the FCPS-1 Prep question bank. Head and neck questions link to topic reviews that show each structure with its relations.

Read next: Anatomy high-yield · Neuroanatomy that repeats · Paper 2 for Surgery & Allied

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