The frontal bone

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The cranium includes all the bones of the head. Altogether, there are 26 cranial bones plus the mandible. Except for the mandible, these bones mostly are fused together so that they do not move. The joints between most of the cranial bones are borders where the bones knit together, called sutures.

The bone of the forehead is called the frontal bone. This bone makes up the superior parts of the eye orbits, extends above the bridge of the nose, wraps around the sides of the forehead and up nearly to the crown of the head.

The frontal bone varies greatly in its anatomy among fossil hominin species and populations. In some, there is a thick bar of bone overlying the orbits, called the supraorbital torus. In many living humans, the frontal bone is thickened over each orbit, more toward the midline of the skull than toward the lateral edges of the orbits. When the bone is thickened in this way, the resulting structure is called a superciliary arch.

As you examine different kinds of hominins, look closely at their supraorbital regions. Which kinds have a clear supraorbital torus?

The frontal bone touches, or articulates with, 12 other cranial bones. Three of these (the ethmoid and left and right lacrimal bones) are on the inside (medial) border of the orbits. Trace your way around the boundary of the frontal bone to find the other nine.

Use your time in the lab to draw a diagram of the skull from the front. Your drawing does not have to be perfect, but you should pay special attention to the boundaries between bones, so that you can label them accurately. Be sure to get the frontal and temporal bones in their correct places, and then use the diagram here to identify the remaining bones.