Platysma

At a glance

English

Platysma

Latin (TA2)

Platysma

System

Muscle

Region

Neck

Side

Paired, left and right

About the platysma

Platysma is a wide, flat muscle of facial expression that spreads over the neck in the superficial fascia, directly under the skin and fat. It is thin enough to be almost transparent in some people, yet it covers most of the front and side of the neck and overlaps sternocleidomastoid. Because it stretches from the chest to the face, it links the expression muscles of the lower face with the skin of the neck.

It begins in the fascia over the upper parts of pectoralis major and deltoid. Its fibres cross the clavicle and run upwards and inwards along the neck. The front fibres of the two sides interlace below and behind the chin, leaving a gap in the midline lower down where the neck has little muscle cover. The rear fibres pass over the mandible: some attach to the bone below its oblique line, others enter the skin of the lower face and blend with the muscles at the corner and lower edge of the mouth. Beneath it lie the external jugular vein, the great auricular and lesser occipital nerves, the facial nerve's marginal mandibular branch, and the lower part of the parotid gland.

When the whole sheet contracts, the skin of the neck wrinkles obliquely and ridges stand out on either side like bowstrings, as in a grimace of strain or fear. The front part, its thickest region, helps pull down the mandible and draws the lower lip and mouth corners down and out, although depressor anguli oris and depressor labii inferioris do most of that work. Its nerve is the facial nerve's cervical branch, and it gets blood from the submental and suprascapular arteries.

Platysma marks an important boundary in neck injuries: a wound that passes through it is classed as penetrating and may reach deep vessels, so it often needs imaging such as CT angiography or exploration. Surgeons divide it in most neck operations and close it carefully afterwards to avoid a puckered scar. With age, its front edges may separate and form visible vertical bands. These can be softened with botulinum toxin or tightened by platysmaplasty. It may also tighten or twitch abnormally after recovery from facial palsy.

Attachments, action and supply

Origin

Fascia over the upper pectoralis major and deltoid.

Insertion

Lower border of the mandible, the skin of the lower face, and the muscles at the corner of the mouth.

Action

Tenses and wrinkles the skin of the neck; helps depress the mandible and draw down the lower lip and mouth corners.

Nerve supply

Facial nerve, cervical branch (CN VII).

Blood supply

Submental and suprascapular arteries.