Spinal accessory nerve

  •  Spinal accessory nerve is a motor nerve. It has two roots, the medullary and spinal.
  • The medullary root arises from the lateral aspect of the medulla by several rootlets behind and in a series with those of the vagus.
  • The spinal root arises from the cervical part of the spinal cord by a series of fasciculi arising from the first five segments that unite to form a trunk and this root enters the cranium through the foramen magnum and joins the medullary root.
  • The nerve thus formed leaves the cranial cavity along with the vagus, through the foramen lacerum and passes downward and backward, leaves the company of the vagus passes under the deep face of mandibular salivary gland passes backward winding round the wing of atlas and divides into dorsal and ventral branches.
  • The dorsal branch passes backward under brachiocephalicus and ramifies on the deep face of trapezius.
  • The ventral branch passes downward across the oesophagus and trachea and supplies sternocephalicus.
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