Cranial nerve 11, spinal cord section

N. accessorius, pars spinalis

M. sternocleidomastoid

That part of the eleventh cranial nerve that originates from the cervical segment of the spinal cord C1 to C6.

The nerve fibre bundle runs upwards along the spinal cord, enters the cranial cavity through the large neck hole, runs a short distance in association with a bundle of thread - n.11's vagus - and leaves the cranial cavity together with n.vagus which after exit takes up the threads of n.11's vagus part. The threads from the spinal cord then find their way to the nodal and coat muscles, i.e. to m. sternocleidomastoid and m.trapezius.

Notice that when m.sternocleidomastoid is activated on one side, the head is turned over to the other side.