Cranial Nerve Nuclei

Cranial Nerve Nuclei

As in the spinal cord, where the anterior horn represents the area of origin of motor fibers and the posterior horn the area of ter-mination of sensory fibers, the medulla ob-longata contains the nuclei of origin (with the cell bodies of efferent fibers) and the nuclei of termination (for the axon termi-nals of afferent fibers), the pseudounipolar cells of which lie in sensory ganglia outside the brain stem. The somatomotor nuclei lie close to the midline:

The nucleus of the hypoglossal nerve (AB1) (tongue muscles)

The nucleus of the abducens nerve (AB2)

The nucleus of the trochlear nerve (AB3)

The nucleus of the oculomotor nerve (AB4) (eye muscles)

The visceromotor nuclei follow laterally, namely, the genuine visceromotor nuclei belonging to the parasympathetic nervous system and the originally visceromotor nu-clei of the transformed branchial arch muscles. The parasympathetic nuclei in-clude:

The dorsal nucleus of vagus nerve (AB5) (viscera)

The inferior salivatory nucleus (AB6) (pre-ganglionic fibers for the parotid gland)

The superior salivatory nucleus (AB7) (pre-ganglionic fibers for the submandibularand sublingual glands)

The Edinger – Westphal nucleus (accessorynucleus of oculomotor nerve) (AB8) (pre-ganglionic fibers for the sphincter muscleof pupil and the ciliary muscle)

The series of motor nuclei of the branchialarch nerves begins caudally with the spinal nucleus of the accessory nerve (AB9) (shouldermuscles), which extends into the cervicalspinal cord. The series continues cranially with the ambiguous nucleus (AB10), which is the motor nucleus of the vagus nerve and the glossopharyngeal nerve (muscles ofpharynx and larynx), and thenucleus of thefacial nerve (AB11) (facial muscles). The facialnucleus lies deep, as do all motor nuclei ofthe branchial arch nerves. Its fibers run in a curve directed dorsally, extend on the floor of the rhomboid fossa (facial colliculus) around the abducens nucleus (internal genuof facial nerve) (A12), and then descendagain to the lower border of the pons where they emerge from the medulla oblongata. The most cranial nucleus of the branchial arch nerves is the motor nucleus of thetrigeminal nerve (AB13) (masticatorymuscles).

The sensory nuclei are located laterally; most medially lies the viscerosensory soli-tary nucleus (AB14), in which the sensoryfibers of the vagus nerve and the glos-sopharyngeal nerve, as well as all taste fibers,terminate. Further laterally extends the nu-clear area of the trigeminal nerve, which has the largest expanse of all cranial nerves and consists of:

The pontine nucleus of the trigeminal nerve(principal sensory nucleus) (AB15)

The mesencephalic nucleus of the trigeminalnerve (AB16)

The spinal nucleus of the trigeminal nerve (AB17)

All fibers of the exteroceptive sensibility offace, mouth, and maxillary sinuses terminatein this area.

Finally, most laterally lies the area of the ves-tibular nucleus (B18) and the cochlear nucleus (B19), in which the fibers of the vestibularroot (organ of balance) and the cochlear root (organ of hearing) of the vestibulocochlearnerve terminate.

A20 Red nucleus.

A21 Olive.