Accessory nerve

The accessory nerve (Latin for " extra nerve" - often with the addition of Willis, the Latinized genitive of the name of its describer of Thomas Willis ) is the XI. Cranial nerve of tetrapods. Like the trigeminal nerve of the accessory nerve is formed from two roots. However, both probably contain only motor fibers.

Radix spinalis

The radix spinalis ( " spinal root " ) comes from the upper cervical segments of the spinal cord. However, it occurs in the lateral region of the spinal cord from the anterior and not on its radix. The fibers have to be referred to their origins in a collection of motor neurons, the motor nucleus nervi as accessorii (also Nucleus principalis nervi accessorii ). The nerve fibers ascend along the spinal cord in the subarachnoid space and pull through the foramen magnum into the posterior cranial fossa.

Radix cranialis

The Radix cranialis ( "Skull root " ) occurs below the vagus nerve out of a gutter ( sulcus posterolateral ) of the medulla oblongata. It gets its so-called " branchiomotorischen " fibers from the nucleus ambiguus, which is also involved in the formation of the glossopharyngeal nerve and the vagus nerve ( cranial nerve IX and X ).

Flow and function

The two roots connect to the accessory nerve and leave the skull accompanied by the vagus nerve through the jugular foramen, pars nervosa ( the glossopharyngeal nerve also pulls through the foramen, however, is separated by a dura mater Bridge, in his own compartment ). In the jugular foramen of the accessory nerve is his " branchiomotorischen " fibers from the Radix cranialis as ramus internus to the vagus nerve from. These fibers, together with some vagal fibers from the nucleus ambiguus of the recurrent laryngeal nerve ( nerve of the sixth branchial arch ) for supplying the inner muscles of the larynx.

The radix spinalis supplied as Ramus externus:

  • The sternocleidomastoid muscle and
  • The trapezius muscle

The sensory innervation (muscle spindles and Golgi tendon organs ) of the two muscles is presumably effected via muscular branches from the cervical plexus.

Fish have these nerves are not distinct, since they have no neck, but rather the fibers to specific spinal muscles supplied head.

I olfactory nerve | II optic nerve | III oculomotor | IV trochlear | V trigeminal | VI Abducens | VII facial nerve | VIII vestibulocochlear nerve | IX glossopharyngeal | X vagus | XI accessory nerve | XII hypoglossal nerve

  • Cranial nerve
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