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Other Terms: Skull, Cranium, Crâne, Schädel, Cráneo
The bones of the skull range from simple, nondescript plates of bone to the most intricate, complex bones of the skeleton. The bones of the skull have a range of important functions. These functions include protecting the delicate brain tissue, fixing the vestibular apparatus of the inner ear in three dimensional space, maintaining open air passageways for respiration, and acquiring and processing food to name a few. It can be divided into two main regions. One region, the cranial vault is the region that surrounds and encases the brain. The other region is the face. This is the area contributing to the orbits, nasal cavity, and oral cavity.
Cranium is a Latin word derived from the Greek word kranion meaning that part of the head containing the brain. Skull comes through the Middle English from the Anglo-Saxon word scealu meaning a cap.
Fibrous joints form most of the articulations in the skull. All three categories of fibrous joint are present with sutures being the most common type. Two synovial joints are present in the skull - the temporomandibular joint and the atlanto-occipital joint.
The skull has a complex developmental history with bones developing both endochondrally and intramembranously. The skull arises from three cranial primordia. These primordia are the chondrocranium, the viscerocranium, and the dermatocranium. The chondrocranium is the cartilaginous base to the skull. This portion of the skull forms the initial supporting plates for the developing brain and the capsules associated with the special sensory structures of the ear, eye, and nose. These regions of the skull ossify endochonrally. The viscerocranium consists of the cartilaginous bars that originally arose as supports for the primitive gill structures. These gill bars become modified in the human skull to form the jaw anatomy, ear ossicles, and the hyoid bone. The largest contribution to the skull is from the dermatocranium. These are bones that form intramembranously in the embryonic mesenchyme. Much of the cranial vault and facial skeleton forms from the dermatocranium.