Muscle · Head

Occipitofrontalis

Musculus occipitofrontalis

One muscle with two bellies at opposite ends of the skull, joined across the top by a tough tendon sheet — the galea. The rear belly grips the back of the skull and the mastoid bone and pulls the whole sheet backwards; the front belly has no bony attachment at all and simply blends into the skin of the eyebrows, so when it shortens it drags the eyebrows up and throws the forehead into horizontal lines. The sheet between them slides freely over the bone as a single unit with the skin and fat above it, which is why the scalp moves as one piece. That same arrangement is why a scalp wound cut across the aponeurosis gapes open — the sheet is held under tension from both ends at once.