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| The skull can be divided into two regions, the cranium and the face (figure 1). The cranium is composed of eight bones: occipital (1), parietal (2), temporal (2), frontal (1), sphenoid (1), and ethmoid (1). The bones of the cranium are separated from each other by joints called sutures. The occipital bone is the most inferior and posterior bone of the cranium. It surrounds the foramen magnum through which the spinal cord enters the cranium. The occipital bone also has various smaller foramena which allow for passage of the cranial nerves and blood vessels (figure 2). The left and right parietal bones form the roof of the cranium. The frontal bone is, of course, the most anterior bone of the cranium. The sphenoid bone is a single bat-shaped bone which forms the anterior base of the cranium. The ethmoid bone is a porous block of bone at the back of the nasal cavities (figure 3). |
Within the left and right temporal bones are three small bones of the middle ear: the malleus, the incus and the stapes.
The face consists of fourteen bones (figure 4): nasal (2), lacrimal (2), inferior nasal conchae (2), palatine (2), vomer (1), zygomatic (2), maxillae (2) and mandible (1). The nasal bones form the roof or "bridge" of the nose. The lacrimal bones form the inside corners of the orbits of the eyes. The inferior nasal conchae, also called turbinates, project into the nasal cavities from the lateral walls. The palatine bones form the anterior roof of the oral cavity. The single vomer sits in the midline, posterior to the palatine bones. The zygomatic bones form the inferior lateral margins of the orbits. The paired maxillae form the upper jaw. In infancy, the lower jaw consists of two bones, but these fuse with age to form the single mandible.
Inferior to the mandible and at the root of the tongue is a single curved bone, the hyoid (figure 5). This bone is not part of the face, but is more properly associated with the skeleton of the larynx.
English - Japanese Glossary
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