platysma

The platysma is a broad, superficial muscle of the anterior neck. It lies within the subcutaneous tissue and the superficial fascia, extending from the lower face into the upper chest. Its fibers run upward from the chest and shoulder region to the lower jaw and mouth.

Anatomy and connections: the muscle arises from the fascia over the upper chest (over the pectoralis major) and the deltoid, and its fibers ascend to insert into the skin and muscles at the angle of the mouth and the lower face. It is commonly described as part of the superficial muscular aponeurotic system (SMAS). The platysma lies superficial to deeper neck muscles and is overlapped by the sternocleidomastoid.

Innervation and blood supply: the platysma is innervated by the cervical branch of the facial nerve (cranial nerve VII). Its blood supply comes from perforating branches of the facial and submental arteries, among others in the area.

Function: the platysma tenses the skin of the neck and helps depress the lower lip and the angle of the mouth, contributing to facial expression. It may assist in depressing the mandible against resistance.

Clinical relevance: with aging, platysmal bands can become visible, contributing to a sagging neck appearance. Procedures such as platysmaplasty or neck lifts target the platysma to improve contour. Developmentally, the muscle arises from the second pharyngeal arch and shares its innervation with other facial expression muscles.