The platysma is a paired flat, superficial neck muscle.
It is counted among the mimic musculature. The platysma extends from the facial skin slightly above the insertions of the lower jaw to about the height of the second rib. It proceeds upward along the front side of the neck crossing the collar bone.
The platysma is a superficially proceeding muscle and – unlike other muscles – directly connected to the skin. It completely covers both front sides of the neck. Due to the direct insertion to the skin it can change the facial expression along with other facial muscles. The platysma belongs – as all other facial muscles – to the group of cross-striated musculature.
In comparison to humans the equivalent of the platysma (e.g. in horses) has a much more important function. For example the platysma in horses helps to get rid of insects by contraction of the skin muscles – a function a human rather does not have to rely on.
The platysma changes the facial expression which plays an important role in human social behavior. In elderly people – when the skin increasingly loses its elasticity – both inner faces of the platysma form two longitudinal wrinkles on the neck.