The frontalis is one of the muscles in the skull. It plays an important role in facial animation, allowing people to alter facial expressions to express emotion, and it is also involved in muscle movements designed to protect the eyes and assist with various visual tasks such as focusing on distant objects. People have two frontalis muscles in a pair, as is seen with most muscles in the body because humans exhibit bilateral symmetry.
This muscle extends from the hairline to the eyebrow. It contains two different parts, the inner and outer frontalis muscle, also known as the medial and lateral parts. The inner portion is responsible for animating the middle of the brow, while the outer segment moves the ends of the eyebrows. These muscles are used to raise the eyebrows and they are also responsible for creating corrugated furrows in the brow, leading to the alternate name “the corrugator” to describe this muscle.
Some texts consider the frontalis muscle to be part of a larger muscle, the epicranius or occipitofrontalis. Others consider it to be an independent muscle. The occipitofrontalis covers the whole top of the head, including the whole scalp and brow. It is used to animate the scalp and upper brow. The tendency to consider the frontalis a part of the occipitofrontalis is more common in modern anatomy references.
This facial muscle is innervated by the seventh cranial nerve. The ability to move the eyebrows is important not just for controlling facial expressions, but for certain activities with the eyes. Moving the brows can help people focus on distant objects and it can shield the eyes from sweat, dirt, and other materials. In people with drooping or saggy eyelids, this muscle can also play a role in pulling the lids back up to allow people to see clearly.
As people age, their frontalis muscles along with other facial muscles can weaken and pull out of alignment. The face as a whole tends to sag, droop, and wrinkle over time. Some people find the signs of aging unsightly and may take steps to change their facial appearance and maintain a more youthful look. One procedure that can be performed is a brow lift to tighten the frontalis muscle, pull the eyebrows back into alignment, and eliminate some of the wrinkling of the forehead that occurs with time. Incisions for this procedure are made in the hairline so they will not be visible once the patient heals.