Page:Anatomy of the Human Body (1918).djvu/129

 I THE OCCIPITAL BONE 129 In the Basle nomenclature, certain bones developed in association with the nasal capsule, viz., the inferior nasal conchæ, the lacrimals, the nasals, and the vomer, are grouped as cranial and not as facial bones. The hyoid bone, situated at the root of the tongue and attached to the base of the skull by ligaments, is described in this section. THE CRANIAL BONES (OSSA CRANII). The Occipital Bone (Os Occipitale). ^H The occipital bone (Figs. 129, 130), situated at the back and lower part of the cranium, is trapezoid in shape and curved on itself. It is pierced by a large oval aperture, the foramen magnum, through which the cranial cavity communicates with the vertebral canal. Constrictor pharyngis superior Fig. 129. — Occipital bone. Outer surface. The curved, expanded plate behind the foramen magnum is named the squama; the thick, somewhat quadrilateral piece in front of the foramen is called the basilar part, whilst on either side of the foramen is the lateral portion. The Squama {squama occipitalis). — The squama, situated above and behind the foramen magnum, is curved from above downward and from side to side. Surfaces. — The external surface is convex and presents midway between the summit of the bone and the foramen magnum a prominence, the external occipital protuberance. Extending lateralward from this on either side are two curved lines, one a little above the other. The upper, often faintly marked, is named the highest nuchal line, and to it the galea aponeurotica is attached. The lower 9