Platysma

The platysma is a superficial muscle of facial expression located in the neck. It lies within the superficial fascia, just beneath the skin — more specifically, as part of the superficial musculoaponeurotic fibrous layer of the face.

Anatomical details

1. Origin

Fascia covering the superior parts of the pectoralis major and deltoid muscles, and the bony clavicle

2. Insertion

Fibres of platysma ascend obliquely to insert into the inferior border of the mandible, the skin of the lower face, and the angle of the mouth. Some fibres also blend with adjacent muscles of fascial expression within the superficial fascial layer.

Innervation

Facial nerve (cranial nerve VII) — specifically, its cervical branch → The platysma is thus part of the muscles of facial expression group.

Actions

• Depresses the mandible slightly (aiding in opening the mouth).

• Draws down the lower lip and angle of the mouth, producing expressions of sadness or fright.

• Tenses the skin of the neck, especially when clenching the teeth or during emotional stress.

Clinical Relevance

• Injury during neck surgery or trauma can damage the cervical branch of the facial nerve, leading to loss of platysma tone and drooping of skin in the neck.