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Model of face. Cutaway model of the human face, seen in profile. The internal carotid artery (red, lower right) supplies the forehead, nose, eyes and middle ear with oxygenated blood. In adults there are 32 teeth (yellow, centre left), which are embedded in the jaw bones. The spherical eyeball (upper left) lies in a cavity in the skull known as an orbit. Its movements are controlled by three pairs of extrinsic muscles (thick brown strips). The nasal cavity (pink, upper left) is lined with a mucous membrane that contains the olfactory cells responsible for smell. (KEYSTONE/SCIENCE PHOTO LIBRARY/VICTOR DE SCHWANBERG)