Platysma

What is the Platysma

The platysma is a broad, thin, paired muscle that covers the front and sides of the neck. It forms part of the superficial layer of the anterior neck muscles, together with the sternocleidomastoid. The platysma lies just beneath the skin within the superficial cervical fascia and can be easily palpated by placing a hand over the area below the chin.

The muscle helps open the mouth and contributes to facial expressions like frowning or tension.

Anatomy

Location and Attachments

Origin	The superficial fascia around the clavicle and the fascial covering of the surrounding muscles.
Insertion	Inferior border of the mandible, the skin around the cheek and lower lip, and the surrounding muscles

Origin

Its fibers arise from the superficial fascia that covers the clavicle and the acromial region, with the origin extending inferiorly to include the fascial layer covering the superior portions of the pectoralis major and deltoid muscles.

From this wide origin, the muscle fibers course medially upward along the sides of the neck, leaving the lower central part of the neck without any muscle covering.

Insertion

Fibers from the left and right platysma muscles meet and merge beneath the chin, near the front of the neck, just behind the mandibular symphysis. It is the midline of the chin, where the two mandible bones fuse during infancy. The central part of the muscle inserts along the inferior border of the mandible, under the oblique line. 

Laterally, the muscle fibers spread toward the mouth, partly inserting into the skin of the cheek and blending with adjacent facial muscles. Some fibers extend to the corners of the mouth, where they blend with the depressor anguli oris and depressor labii inferioris muscles, contributing to the formation of the modiolus, the point at the corner of the mouth that controls movement and expression.

Relations With Surrounding Muscles and Structures

It lies within the superficial layer of the cervical fascia, positioned between the skin and the deep cervical fascia. It extends upward across the anterior surface of the neck, overlying the lower part of the sternocleidomastoid muscle. The parotid gland, the largest salivary gland in the human body, lies deep to the muscle on both sides of the mouth.

Deep to the platysma lie several neurovascular structures, most notably the external and anterior jugular veins, the cervical branch of the facial nerve, and other smaller cutaneous nerves.

Function

Action

Draws the corners of the mouth to help produce facial expressions

Facial Expression

Because it attaches to the lower mandible, lower lip, modiolus, and blends with muscles around the mouth, the platysma helps pull down the corners of the mouth and the lower lip, contributing to expressions of sadness, surprise, horror, and other emotions by downward movement of the corners of the mouth and the lips.

Neck Action

When the platysma contracts fully, it tenses the skin of the neck, producing characteristic oblique wrinkles along the sides. This function becomes particularly evident during activities like shaving or when the neck skin is tightened. It helps stabilize the neck and protects the underlying structures when the jaw and mouth move.

Jaw and Mouth Movement

Due to its attachment to the mandible, the muscle assists in depressing the lower jaw and keeping the mouth open, such as during brushing teeth or during a dental examination. 

Antagonists

Two main muscles of mastication, the masseter and temporalis, act as primary antagonists of the platysma, as they elevate the mandible to close the jaw, opposing the platysma’s action of depressing the mandible and tensing the neck.

Innervation

Nerve

Cervical branch of the facial nerve

The platysma receives its motor supply from the cervical branch of the facial nerve, arising from the cranial nerve VII. It also obtains proprioceptive input via the transverse cervical nerve, which originates from the cervical plexus.

Blood Supply

Artery

Submental artery and suprascapular artery

Blood supply to the muscle primarily comes from the submental artery, a branch of the facial artery. The suprascapular artery, which branches from the thyrocervical trunk, also provides blood supply to the muscle.