Platysma

Where is the platysma?

It arises from the fascia over the upper parts of the deltoid and pectoral muscles. Its fibers cross the clavicle and climb the neck at a slant. (StatPearls, Platysma)

Right under it lie the sternocleidomastoid and the digastric. Toward the midline, the first layer of strap muscles covers the larynx and thyroid beneath it. (StatPearls, Platysma)

Above, it is continuous with the superficial musculoaponeurotic system (SMAS), the fascial layer of the face that runs from the platysma up to the scalp. (StatPearls, Facial Muscles)

Where does the platysma insert?

It inserts on the mandible, the skin of the cheek, the corner of the mouth, the orbicularis oris and the back edge of the depressor anguli oris. Its only bony insertion is small, on the front third of the mandible. (StatPearls, Platysma)

The depressor anguli oris, which pulls down the corner of the mouth, is a continuation of the platysma. (StatPearls, Facial Muscles)

What does the platysma do?

Its role is still debated. It can wrinkle the skin of the neck, and in some people it pulls down the lower lip and the corner of the mouth a little, though the depressor anguli oris and depressor labii inferioris do most of that work. (StatPearls, Platysma)

Contracting, it raises vertical platysmal bands on the neck and lowers the mandible, which makes the neck shorter and wider. StatPearls links this to expressions of surprise, horror or disgust. (StatPearls, Platysma and Facial Muscles)

Which nerves and vessels lie with the platysma?

The cervical branch of the facial nerve supplies it, and in some people the marginal mandibular branch supplies some of its fibers. (StatPearls, Platysma and Facial Muscles)

Just under it on the side of the neck run the external jugular vein and the great auricular nerve. Higher up, the marginal mandibular branch of the facial nerve lies under its upper part. (StatPearls, Platysma)

The supraclavicular nerves, which carry sensation from the lower neck and upper chest, pierce its lower part just above the clavicle. (StatPearls, Platysma)

How does the platysma vary?

Under the chin, the inner fibers of the two sides interlace for 1 to 2 cm in 75% of people and all the way down to the thyroid cartilage in 15%; in 10% they do not interlace. (StatPearls, Platysma)

Its thickness varies with sex, age and size. In some people it is missing from parts of the neck or very thin. (StatPearls, Platysma)

Where the sources differ

StatPearls’ platysma article gives its blood supply as branches of the external carotid artery. Its facial muscles article agrees for part of the muscle, through the submental branch of the facial artery, but names the suprascapular artery for the rest. (StatPearls, Platysma and Facial Muscles)