Anatomy chapters
Nerves and vessels of the head and neck
The carotid arteries and their branches, the veins of the head and neck, and the nerves examiners test most: facial, trigeminal, the last four cranial nerves, the cervical plexus and the sympathetic chain.
- The common carotid divides level with the top of the thyroid cartilage (C3–C4) into internal (no branches in the neck) and external carotids.
- The external carotid has eight branches; the middle meningeal (from the maxillary) is the one in extradural haemorrhage.
- Nerve lesions in the neck give classic signs: tongue deviation (XII), shoulder droop (XI), hoarse voice (recurrent laryngeal) and Horner's syndrome.
On this page
Overview
The head and neck are supplied mainly by the carotid arteries and drained by the jugular veins.
Twelve cranial nerves and the upper cervical nerves supply the region. The ones examiners test most are those with obvious signs when damaged.
The carotid arteries
The right common carotid arises from the brachiocephalic trunk. The left arises directly from the arch of the aorta.
In the neck it lies inside the carotid sheath, with the internal jugular vein on its lateral side and the vagus nerve behind, in the groove between them.
Level with the top of the thyroid cartilage (C3–C4), it divides into the internal and external carotid arteries.
- Carotid sinus: a widening at the start of the internal carotid. It senses blood pressure (baroreceptor).
- Carotid body: a small mass at the bifurcation. It senses oxygen and carbon dioxide (chemoreceptor).
Both are supplied mainly by the glossopharyngeal nerve.
Pressing on the carotid sinus slows the heart and lowers blood pressure. Carotid sinus massage is used to stop some fast heart rhythms.
External carotid artery
It supplies the face, scalp, neck and the outside of the skull. It has eight branches.
| Branch | Supplies |
|---|---|
| Superior thyroid | Thyroid gland and larynx |
| Ascending pharyngeal | Pharynx |
| Lingual | Tongue |
| Facial | Face; it is felt crossing the lower border of the mandible in front of masseter |
| Occipital | Back of the scalp |
| Posterior auricular | Behind the ear |
| Maxillary (terminal) | Deep face, jaws, teeth, nose; gives the middle meningeal artery |
| Superficial temporal (terminal) | Scalp over the temple; pulse felt in front of the ear |
"Some Anatomists Like Freaking Out Poor Medical Students": superior thyroid, ascending pharyngeal, lingual, facial, occipital, posterior auricular, maxillary, superficial temporal.
The middle meningeal artery enters the skull through the foramen spinosum. Its anterior branch lies under the pterion; a blow there tears it and causes an extradural haemorrhage.
Internal carotid artery
It has no branches in the neck. It enters the skull through the carotid canal, passes through the cavernous sinus, and divides into the anterior and middle cerebral arteries.
Its branches inside the skull include the ophthalmic artery (to the eye, including the central artery of the retina) and the posterior communicating artery. See blood supply of the brain and spinal cord.
Veins
The internal jugular vein starts at the jugular foramen, carrying on from the sigmoid sinus. It descends inside the carotid sheath and joins the subclavian vein to form the brachiocephalic vein.
The external jugular vein starts just behind the angle of the jaw and runs down across sternocleidomastoid. It is visible in the neck and rises when venous pressure is high.
The cavernous sinus
A pair of venous spaces, one each side of the sphenoid body.
| In the lateral wall (top to bottom) | Through the sinus itself |
|---|---|
| Oculomotor (III) | Internal carotid artery |
| Trochlear (IV) | Abducent nerve (VI) |
| Ophthalmic (V1) | |
| Maxillary (V2) |
The abducent nerve (VI) runs through the middle of the sinus, so it is usually the first nerve affected by cavernous sinus thrombosis or an aneurysm there.
See danger area of the face and scalp for how infection reaches this sinus.
Key nerves
Trigeminal nerve (V)
The main sensory nerve of the face. Its three divisions are the ophthalmic (V1), maxillary (V2) and mandibular (V3). Only V3 has motor fibres, to the muscles of mastication.
Facial nerve (VII)
Supplies the muscles of facial expression, taste to the front two-thirds of the tongue, and the submandibular, sublingual and lacrimal glands. See muscles of facial expression and mastication.
Glossopharyngeal nerve (IX)
Taste and general sensation from the back third of the tongue, sensation from the pharynx (the sensory side of the gag reflex), the carotid sinus and body, and secretomotor fibres to the parotid gland.
Vagus nerve (X)
Gives motor supply to the pharynx, soft palate and larynx. Its recurrent laryngeal branch supplies every laryngeal muscle except cricothyroid.
The right recurrent laryngeal nerve hooks under the subclavian artery. The left hooks under the arch of the aorta, so it is longer and more often damaged.
Damage to a recurrent laryngeal nerve (for example, in thyroid surgery) causes a hoarse voice.
Accessory nerve (XI)
Supplies sternocleidomastoid and trapezius. In the posterior triangle it lies superficially, so it is easily cut in lymph node biopsy.
Damage causes a drooping shoulder and weak shrugging.
Hypoglossal nerve (XII)
Supplies all the muscles of the tongue except palatoglossus. With a lower motor neuron lesion, the tongue wastes on that side and deviates towards the side of the lesion when protruded.
The tongue points towards the side of a hypoglossal nerve lesion, because the healthy genioglossus pushes it across.
Cervical plexus
Formed by the ventral rami of C1 to C4.
- Sensory branches (lesser occipital, great auricular, transverse cervical, supraclavicular) emerge near the middle of the back of sternocleidomastoid. This point is used for a superficial cervical plexus block.
- Ansa cervicalis (C1–C3) supplies most of the infrahyoid (strap) muscles.
- Phrenic nerve (C3, C4, C5) runs down on scalenus anterior to supply the diaphragm.
"C3, 4, 5 keeps the diaphragm alive."
Cervical sympathetic trunk
In the neck the sympathetic chain carries three ganglia: superior, middle and inferior. The inferior one commonly merges with the first thoracic ganglion as the stellate ganglion.
Clinical relevance
Horner's syndrome
How it happens: damage to the sympathetic supply of the head, for example from a lung apex (Pancoast) tumour, neck surgery or a stellate ganglion block.
What you see: ptosis (drooping upper lid), miosis (small pupil), anhidrosis (no sweating) on that side of the face, and apparent sinking of the eye.
Extradural haemorrhage
How it happens: a blow to the side of the head fractures the thin bone at the pterion and tears the middle meningeal artery.
What you see: often a short lucid interval, then drowsiness, a dilated pupil on the same side and coma unless treated.
The common angles are: the level of the carotid bifurcation, the branches of the external carotid, the middle meningeal artery and pterion, the contents of the cavernous sinus, the signs of XI and XII lesions, recurrent laryngeal nerve injury and Horner's syndrome.
Quick revision
- Carotid bifurcation: upper border of thyroid cartilage (C3–C4).
- Internal carotid: no branches in the neck.
- External carotid: eight branches; maxillary gives the middle meningeal (foramen spinosum).
- Cavernous sinus: III, IV, V1, V2 in the wall; ICA and VI inside.
- XI: sternocleidomastoid and trapezius. XII: tongue deviates to the side of the lesion.
- Phrenic: C3, 4, 5. Horner's: ptosis, miosis, anhidrosis.
Written by The House Job from standard anatomy references (Snell's Clinical Anatomy by Regions is the book named in the UHS PGET syllabus).
FAQ
At what level does the common carotid artery divide?
At the upper border of the thyroid cartilage, about C3 to C4.
Which artery causes an extradural haemorrhage?
Usually the middle meningeal artery, torn by a fracture at the pterion.
Which nerve is first affected in cavernous sinus thrombosis?
The abducent nerve (VI), because it runs through the sinus itself.
What are the signs of Horner's syndrome?
Ptosis, a small pupil and loss of sweating on the same side of the face.