frontoparietalis

Frontoparietalis is a term used in anatomy to describe a muscle or muscular sheet that extends from the frontal region toward the parietal area of the scalp. Its recognition and precise boundaries vary among species. In humans, the frontoparietalis is not universally treated as a distinct, independent muscle; instead, its fibers are often considered part of the frontalis or the broader occipitofrontalis complex, and its development can be variable. In other mammals, however, the frontoparietalis can present as a more distinct layer or muscle that connects the frontal region to the parietal area and contributes to movements of the scalp.

Anatomy and relationships: when described as a separate structure, the frontoparietalis lies superficially to the parietal region and may blend with adjacent scalp muscles and the galea aponeurotica. Its fibers are typically thought to run from the frontal bone toward the parietal bones, integrating with surrounding musculature involved in scalp mobility.

Innervation and function: when identifiable as part of the frontal-muscle complex, the frontoparietalis is generally innervated by branches of the facial nerve (cranial nerve VII). Functionally, it participates in scalp movement and may assist in facial expressions by tensioning the scalp over the frontal and parietal regions.

Development and evolution: the frontoparietalis reflects the variability of head musculature across mammals. It is viewed as more prominent or distinct in some species and less so in humans, highlighting evolutionary divergence in the muscular plan of the scalp.

See also: occipitofrontalis, frontalis, galea aponeurotica, temporoparietalis.