The human head contains twenty-two different bones. The face, consisting of fourteen different bones, gives the front of the head its shape and structure. The cranium, also referred to as the skull, is comprised of eight separate plate-like bones. Located at the top of the head, the cranium, a collection of eight separate bones, encloses the brain for protection. The sagittal crest is located at the uppermost portion of the skull where bones come together and form a ridge.
Bones are made up of osseous or hardened connective tissue that makes them rigid and strong. Throughout the body, bones allow the body to maintain its shape. Bones also provide a stable base for the attachment of soft tissue, muscles and their supporting structures. The cranial bones are slightly curved and flatter than the rest of the bones in the body. These hard bowl-shaped bones form a slight elevation or rim called the sagittal crest that runs from the top of the forehead to the back of the skull.
Running lengthwise from the front to the back of the head, the sagittal crest of the skull is the main attachment for the temporalis muscle. The temporalis is a large muscle located on each side of the face behind the eyes. This long fan-shaped muscle is the main component in the process of mastication or chewing by also connecting to the jaw.
The smallest portion of the temporalis muscle attaches to the coronoid process of the mandible, a thin triangle projection located on the lower jaw. Then it progressively expands upwards to the top of the head where it fastens to the sagittal crest. Since this muscle adheres to the immobile skull bones, contraction or tightening and shortening of the muscle allow the jaw to open and close. It also provides the jaw with enough strength to chew or crush food items.
Stronger muscles require sturdier bony attachments to support the powerful lengthening and shortening of the muscle fibers for effective movement. The size or projection of the sagittal crest is dependent of the size and strength of the temporalis muscles. On average, men typically have a slightly larger sagittal crest than women. This is due to the increase in muscle bulk and power.
Overall, however, as humans have evolved, the size of the sagittal crest has significantly decreased. This can be contributed to major changes in diet during modern times. This includes not only the variety of foods but also the way it is prepared, as life today no longer necessitates the eating of raw food stuffs or freshly killed animals to provide sustenance to the body.