In humans, the occipitofrontalis helps to create facial expressions.

The frontal belly receives blood from the supraorbital and supratrochlear arteries, while the occipital belly receives blood from the occipital artery.

[5] The occipitofrontalis muscle helps to create facial expressions.

[4][2] Damage to the facial nerve can cause atony of the occipitofrontalis muscle.

In apes, however, the head is not balanced on the vertebral column, and apes therefore need strong muscles that pull back on the skull and prominent supraorbital ridges for the attachment of these muscles.