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• VI. The abducent nerve (see Fig. 56.3): leaves the brain at the pos-
the neck the vagus (and cranial root of the accessory) gives the follow-
terior border of the pons and has a long intracranial course (so is often
ing branches:
the first nerve to be affected in raised intracranial pressure) to the cav-
• The pharyngeal branch which runs below and parallel to the glos-
ernous sinus, where it is closely applied to the internal carotid artery, the thorax where its further course is described in Chapters 2 and 3. In
and thence to the orbit via the superior orbital fissure. It supplies the lat- sopharyngeal nerve and supplies the striated muscle of the palate
eral rectus. and pharynx.
• VII. The facial nerve (Fig. 58.1): this leaves the brain near the cere- • Superior and inferior cardiac branches which descend into the
bellum and passes laterally into the internal auditory meatus. It reaches thorax to take part in the cardiac plexuses.
the medial wall of the middle ear and turns backwards and down- • The superior laryngeal nerve which divides into internal and exter-
wards to leave the skull via the stylomastoid foramen. It then traverses nal laryngeal nerves. The former enters the larynx by piercing the
the parotid gland, in which it divides into five branches (temporal, thyrohyoid membrane and is sensory to the larynx above the level of
zygomatic, buccal, marginal mandibular and cervical) which are the vocal cords, and the latter is motor to the cricothyroid muscle.
distributed to the muscles of facial expression, the platysma and the • The recurrent laryngeal nerve. On the right side it loops under the
posterior belly of the digastric. In the middle ear it gives off the greater subclavian artery before ascending to the larynx behind the com-
petrosal branch which carries parasympathetic fibres to the mon carotid artery. On the left side it arises from the vagus just
sphenopalatine ganglion and thence to the lacrimal gland. In the middle below the arch of the aorta and ascends to the larynx in the groove
ear it also gives off the chorda tympani which joins the lingual nerve between the trachea and oesophagus. The recurrent laryngeal
and is distributed with it. Sensory fibres in the chorda tympani have nerves supply all the muscles of the larynx except for cricopharyn-
their cell bodies in the geniculate ganglion which lies on the facial geus and are sensory to the larynx below the vocal cords.
nerve where it turns downwards. • XI. The accessory nerve (Fig. 58.2): the cranial root arises from the
• VIII. The vestibulocochlear (auditory) nerve: this leaves the brain side of the medulla with the vagus and is distributed with it. The spinal
next to the facial nerve and enters the internal auditory meatus. It root arises from the side of the upper five segments of the spinal cord,
divides into vestibular and cochlear nerves. enters the cranial cavity through the foramen magnum and joins the
• IX. The glossopharyngeal nerve (see Fig. 65.1): leaves the brain at vagus. It leaves the vagus below the jugular foramen and passes back-
the side of the medulla and passes through the jugular foramen. It then wards to enter sternomastoid, which it supplies. It then crosses the pos-
curves forwards between the internal and external carotid arteries to terior triangle to supply trapezius (see Fig. 61.3).
enter the pharynx between the superior and middle constrictors. It sup- • XII. The hypoglossal nerve (Figs 59.1 and 65.1): arises from the
plies sensory fibres to the posterior one third of the tongue (including side of the medulla ventral to the vagus and cranial accessory and
taste) and the pharynx. It also gives a branch to the carotid body and passes through the hypoglossal canal. Below the skull it is joined by the
sinus. anterior ramus of C1 and it then runs downwards and forward, across
• X. The vagus nerve (Fig. 58.2): arises from the side of the medulla the carotid sheath and the upward loop of the lingual artery to enter the
and passes through the jugular foramen. It is joined by the accessory tongue. It supplies the intrinsic and extrinsic muscles of the tongue. It
nerve but the spinal root of the accessory leaves it again almost imme- gives off the descendens hypoglossi but this is actually composed of
diately. The cranial root is distributed with the vagus (hence the fibres from C1. This joins the descendens cervicalis, derived from C2
nameait is accessory to the vagus). The vagus carries two ganglia for and 3, to form the ansa cervicalis. From this, branches arise to supply
the cell bodies of its sensory fibres. It descends between the internal the ‘strap muscles’, i.e. sternothyroid, sternohyoid, thyrohyoid and
carotid artery and the jugular vein, within the carotid sheath, and enters omohyoid.

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