OCCIPITAL BONE
\ˈɒksɪpˌɪtə͡l bˈə͡ʊn], \ˈɒksɪpˌɪtəl bˈəʊn], \ˈɒ_k_s_ɪ_p_ˌɪ_t_əl b_ˈəʊ_n]\
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By Princeton University
By DataStellar Co., Ltd
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Is situate at the posterior and inferior part of the cranium, which it assists in forming. It is flat, symmetrical, and curved upon itself. It presents, 1. An occipital or posterior surface, which is convex, and has, upon the median line, the basilary surface, the foramen magnum, through which passes the spinal marrow with its membranes and vessels,-the external occipital crest, the external occipital protuberance; and, at the sides, the upper curved line, large rough arched ridge or transverse arch or linea semicircularis, the lower curved line, the posterior condyloid fossae, the condyles for the articulation of this bone with the atlas; and the anterior condyloid fossae, pierced by a foramen for the passage of the ninth pair of nerves. 2. A cerebral or anterior surface. On the median line are: the basilary fossae, the inner orifice of the foramen magnum, the internal occipital crest, the internal oceipital protuberance, the cruciform spine; a channel, which lodges the termination of the straight sinus, and on each side, the occipital fossae, distinguished into superior or cerebral, and inferior or cerebellous, and separated by a groove which lodges the lateral sinus. 3. The surfaces of the occipital bone are separated by four ridges and four angles. The two superior edges are articulated with the parietal bones; the two lower join the temporal; and the anterior angle, under the name basilary process, is united to the sphenoid. The occipital bone is developed from four points of ossification; and sometimes from a greater number.
By Robley Dunglison
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A rhomboidal b. situated at the lower and back part of the cranium. At birth this b. consists of five pieces, the basi-occipital, the two exoccipitals, the supra-occipital, and the interparietal, all of which are fused into one piece at about the sixth year
By Smith Ely Jelliffe
