The platysma is visible, with skin removed.
The muscles of the face, platysma visible at bottom right.
|subcutaneous tissue of infraclavicular and supraclavicular regions|
|base of mandible; skin of cheek and lower lip; angle of mouth; orbicularis oris|
|branches of the Submental artery and Suprascapular artery|
|cervical branch of the facial nerve (CN VII)|
|Actions||Draws the corners of the mouth inferiorly and widens it (as in expressions of sadness and fright). Also draws the skin of the neck superiorly when teeth are clenched|
|Anatomical terms of muscle|
It is a broad sheet arising from the fascia covering the upper parts of the pectoralis major and deltoid; its fibers cross the clavicle, and proceed obliquely upward and medially along the side of the neck.
The anterior fibers interlace below and behind the symphysis menti, with the fibers of the muscle of the opposite side; the posterior fibers cross the mandible, some being inserted into the bone below the oblique line, others into the skin and subcutaneous tissue of the lower part of the face. Many of these fibers blend with the muscles about the angle and lower part of the mouth.
Sometimes fibers can be traced to the zygomaticus,[disambiguation needed] or to the margin of the orbicularis oris. Beneath the platysma, the external jugular vein descends from the angle of the mandible to the clavicle.
Variations occur in the extension over the face and over the clavicle and shoulder; it may be absent or interdigitate with the muscle of the opposite side in front of the neck; attachment to clavicle, mastoid process or occipital bone occurs. A more or less independent fasciculus, the occipitalis minor, may extend from the fascia over the trapezius to fascia over the insertion of the sternocleidomastoideus.
The platysma is supplied by cervical branch of the Facial nerve (CN VII).
When the entire platysma is in action it produces a slight wrinkling of the surface of the skin of the neck in an oblique direction. Its anterior portion, the thickest part of the muscle, depresses the lower jaw; it also serves to draw down the lower lip and angle of the mouth in the expression of melancholy, i.e. grimacing. However, the platysma plays only a minor role in depressing the lip which is primarily performed by the depressor anguli oris and the depressor labii inferioris.
- Anatomy & Physiology, 8th Edition, McGraw-Hill Co., 2008.