external bones of cranium.docx - Bones of the Cranium...

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Bones of the Cranium Occipital bone (1) Parietal bones (2) Temporal bones (2) Frontal bone (1) Occipital Bone Forms the back and base of the skull and is the cradle for the brain. It articulates with C1 (the atlas), the parietal bones, and temporal bones. Its opening is the foramen magnum. External Occipital Protuberance Also known as the E.O.P., it is located at the base of the skull, lying midway between the foramen magnum and the summit of the occipital bone. Superior Nuchal Line Extends laterally on both sides of the E.O.P. This is the origin of the occipitofrontalis muscle. Parietal Bones Makes up the superior portion of the sides and back of the cranium. Comprises two thirds of the roof of the skull and articulates with the temporal, occipital, and frontal bones. The parietal bones go in two directions, vertical at the sides and horizontal at the top. The parietal bone changes direction at the parietal eminences. Parietal Eminences Where the parietal bones change direction. The distance between the two parietal eminences marks the widest portion of the skull. Temporal Bones The thinnest bones protecting the brain. Located behind the lateral borders of the eye sockets. The temporal bones create the inferior portion of the sides and base of the skull and articulate with the parietal and occipital bones. Squamous Portion of the Temporal Bone Smooth and convex, it extends medially and deep behind the zygomatic arch. Also considered the vertical portion of the bone, it is the anterior and superior portion of the bone. Temporal Cavity The greatest depth of the temporal cavity is located posterior to the lateral rim of the eye socket. Zygomatic Arch Comprised of the the zygomatic process of the temporal bone and the temporal process of the zygomatic bone. The widest part of the face is measured from one zygomatic arch to the other zygomatic arch. Mandibular Fossa Depression in the temporal bone that articulates with the mandibular condyle. Mastoid Process Conical projection posterior and inferior to the mandibular fossa. It serves as a point of attachment for the sternocleidomastoid muscle. External Auditory Meatus Ear passage (meatus means "passageway"). The most accurate location of the ear. It is protected by a small flap of skin called the tragus.
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