Corpus: Occipitofrontalis muscle

The occipitofrontalis muscle, part of the epicranial muscles, consists of two muscle bellies located at opposite ends of the skull, connected by the galea aponeurotica. It is classified as part of the mimic musculature.

The frontal belly of the muscle originates at the supraorbital margin of the frontal bone and the area around the glabella. Its fibers extend into neighboring facial muscles, including the procerus, corrugator supercilii, and orbicularis oculi muscles.

The occipital belly originates from the highest nuchal line of the occipital bone and, to a lesser extent, from the temporal bone.

The fibers of both muscle bellies run vertically upward and insert into the galea aponeurotica, the tendinous sheet covering the top of the skull.

Both muscle bellies have an almost quadrangular shape. The frontal belly of the occipitofrontalis muscle is more prominent and contains longer fibers.

The frontal belly of the occipitofrontalis muscle is innervated by the temporal branches of the facial nerve, while the occipital belly is innervated by the posterior auricular nerve, also a branch of the facial nerve.

Contraction of the frontal belly raises the eyebrows and creates horizontal folds in the forehead, commonly associated with expressions of surprise or frowning. The occipital belly pulls the galea aponeurotica backward, stretching it. Together, both bellies facilitate the movement of the scalp.

Due to the tension exerted by the occipitofrontalis and temporoparietalis muscles on the galea aponeurotica, scalp injuries often result in gaping wounds.