Platysma Muscle Information
The platysma is a superficial muscle that overlaps the sternocleidomastoid.
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 oculi. Beneath the platysma, the external jugular vein descends from the angle of the mandible to the clavicle.
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Variations
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.
Nerve
The platysma is supplied by the Facial nerve (CN VII).[1]
Actions
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.
External links
- Platysma+muscle at eMedicine Dictionary
Additional images
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Mandible. Outer surface. Side view.
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Veins of the head and neck.
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The nerves of the scalp, face, and side of neck.
References
- ^ Anatomy & Physiology, 8th Edition, McGraw-Hill Co., 2008.
External links
This article was originally based on an entry from a public domain edition of Gray's Anatomy. As such, some of the information contained within it may be outdated.
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Categories: Muscles of the head and neck
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