platysma (subcutaneous colli, tetragonus)

Introduction

Facial muscle in the neck.

Origin

• subcutaneous layer & fascia covering pectoralis major & deltoid at level of 1st or 2nd rib

Insertion

• lower border of mandible, risorius & platysma of opposite side

Action

• depresses lower lip
• forms ridges in skin of neck & upper chest when jaws are clenched, conveying emotions of stress or anger

Innervation

cervical branch of facial nerve (CN VII)

More general terms

• skeletal muscle (voluntary muscle)