SKULL.—The skull consists of 28 bones (figs.1-15 and 1-16), 22 of which form the framework of thehead and provide protection for the brain, eyes, andears; six are ear bones. With the exception of the lowerjaw bone and the ear bones, all skull bones are joinedtogether and fixed in one position. The seams wherethey join are known as sutures. The bones of the skullare classified as either cranial or facial bones.Cranial Bones.—The cranium is formed by eightmajor bones, most of which are in pairs (fig. 1-15). Thefrontal bone forms the forehead and the roof of eachorbit (or eye socket) and the nasal cavity. The parietalbones form the roof of the skull. The temporal boneshelp form the sides and base of the skull and also housethe auditory and hearing organs. The occipital boneforms part of the base and back of the skull, andcontains a large hole called the foramen magnum. Thisopening permits passage of the spinal cord from thecranium into the spinal column. The sphenoid bonesare wedged between several other bones in the anteriorportion of the skull. These bones help form the base ofthe cranium, the sides of the skull, and the floors andsides of the orbits. The ethmoid bones are located infront of the sphenoid bone. They form sections of thenasal cavity roof, the cranial floor, and the orbital wall.Facial Bones.—The facial bones of the skullconsists of 14 bones: 13 immovable bones and amovable lower jawbone (fig. 1-16). The facial bonesgive the face its basic shape and provide attachmentsites for various muscles that move the jaw and controlfacial expressions.1-8HM3F0114EPIPHYSEALDISKSPROXIMALEPIPHYSISARTICULARCARTILAGESPACE OCCUPIEDBY RED MARROWCANCELLOUSTISSUECOMPACTBONEMEDULLARYCANALYELLOWMARROWPERIOSTEUMDIAPHYSISDISTALEPIPHYSISSPONGYBONEFigure 1-14.—Anatomy of a long bone.HM3f0115MENTALFORAMENMANDIBLECORONALSUTUREFRONTALBONESPHENOIDBONEETHMOIDBONELACRIMALBONENASALBONEZYGOMATICBONEINFRAORBITALFORAMENZYGOMATIC PROCESSOF TEMPORALTEMPORAL PROCESSOF ZYGOMATICOCCIPITALBONETEMPORALBONELAMBDOIDALSUTURESQUAMOSALSUTUREPARIETALBONEMAXILLAFigure 1-15.—Lateral view of the skull.
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