Platysma

Origin, Insertion, Action & Nerve

Attachments explained

The Platysma is defined first by where it attaches. Its origin is the more fixed anchor, usually the proximal or more stable end that stays put during contraction, while its insertion is the more mobile point that is pulled toward the origin when the muscle shortens.

Action & function

When the Platysma contracts, it produces the following movements: Depresses mandible and lower lip; tenses skin of the neck.

As part of the Facial Expression group of the Head & Neck, it works alongside neighbouring muscles to generate smooth, coordinated movement and to stabilise the structures it acts on.

Nerve supply & clinical relevance

The Platysma receives its nerve supply from the Cervical branch of facial nerve (CN VII).

Because a muscle can only contract when its nerve is intact, injury to the Cervical branch of facial nerve can weaken or paralyse the Platysma, impairing the movements it normally produces (depresses mandible and lower lip). This is why knowing the innervation is central to localising nerve lesions in clinical practice.

How to study the Platysma (the OIANS method)

Treat the platysma as the muscle of facial expression that has migrated onto the neck. Because it lies in the superficial fascia and reaches from the upper chest to the lower face, contracting it wrinkles the skin of the neck into visible cords and pulls the corners of the mouth downward, the grimace of sudden alarm; visualising that skin-tensing sheet fixes its action.

Remember it is supplied by the cervical branch of the facial nerve (CN VII), which keeps it firmly in the facial-expression family despite its position low in the neck. Contrast it with the deeper strap and scalene muscles of the neck, which are driven by cervical spinal nerves, so nerve supply is the cleanest way to categorise it correctly.

Frequently asked questions

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