platysma muscle (anatomy)
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The platysma are one of the muscles of facial expression. Its actions include:

  • wrinkling of the skin of the lower face and mouth
  • drawing the corners of the mouth inferiorly
  • assisting in opening of mouth by depressing the mandible

On both sides, it is a wide, sheet of skeletal muscle which originates from the deep fascia and skin upon the lower neck and upper chest; it extends laterally to the anterior surface of the deltoid muscles. Its fibres pass superomedially to:

  • converge with:
    • each other in the midline inferior to the chin
    • other muscles of facial expression at the corners of the mouth e.g. depressor labii inferioris and depressor anguli oris
  • insert into the:
    • inferior border of the mandible
    • skin of the face inferior to the mouth

By taking this course, platysma covers parts of the anterior and posterior triangles of the neck and the external and anterior jugular veins.

The nerves to platysma are:

  • efferent: cervical branch of facial nerve (VII)
  • afferent: transverse cervical nerve (C2,C3) - proprioceptive fibres