Bones of the Skull. 



Planum occipitale 

 Linea nuchae suprema 



Linea nuchae superior 



Protuberantia occipitalis- - 

 externa 



Crista occipitalis externa - 

 Planum nuchale 



Linea nuchae inferior . 



Squama occipitalis 



Processus jugularis 

 1 Incisura jugularis 



Processus intrajugularis 



Pars hasilaris 



Fossa coudyloidea 

 Canalis condyloideus 



; Tuberculum pharyngeum 

 Canalis hypoglossi 



Condylus occipitalis 



3. Occipital bone, OS OCCipitale, viewed from the right side. 



(The direction does not correspond to that of the bone when the skull is in its ordinary position.) 



The squama occipitalis (see also Figs. 1, 2, 55, 56 and 59 66) is curved so as to be 

 convex backward in the sagittal and transverse direction. Its anterior border forms the 

 posterior periphery of the foramen occipitale magnum; the free lateral and superior borders meet 

 in the median plane, the lower portion of each lateral border being slightly serrated as the 

 continuation of the margo mastoideus (p. 2); the upper portion of this border is deeply and 

 multiply serrated and is known as the margo lambdoideus, for union with the occipital 

 margin of the parietal bone (sutura lambdoidea). Projecting from the middle of the posterior 

 surface is seen the external occipital protuberance (protuberantia occipitalis externa). Extend- 

 ing lateralward from this protuberance on each side are the superior nuchal lines (lineae 

 nuchae superiores) , convex upward , and above these the less constant supreme nuchal lines 

 (lineae nuchae supremae). In the median plane, extending toward the foramen magnum, is 

 seen the external occipital crest (crista occipitalis externa) which gives attachment to the 

 ligamentum nuchae. From about the middle of the crest extend lateralward the two inferior 

 nuchal lines (lineae nuchae inferiores) , also convex upward. The area for the m. occipitalis 

 above the external protuberance and the supreme nuchal lines is called the occipital plain 

 (planum occipitale), while that below the same is designated the nuchal plain (planum nuchale) 

 and gives attachment to the mm. trapezius, sternocleidomastoideus, splenius capitis, semispinalis 

 capitis, obliquus capitis superior, recti capitis posteriores. On the anterior- surface of the bone 

 at the middle point of the eminentia cruciata, nearly corresponding in position to the external 

 protuberance, is seen the internal occipital protuberance or protuberantia occipitalis internet 

 (for the confluens sinuum ; falx cerebri, and tentorium cerebelli). From the internal protuberance 

 arise three well marked grooves: one in the median line passes upward, the sulcus sagittalis 

 (0. T. superior longitudinal sulcus) for the sinus sagittalis superior and the falx cerebri: and 

 one lateralward on each side, the sulcus transversus (for the sinus transversus; tentorium 

 cerebelli). Of the two transverse sulci the right is usually wider than the left and it alone 

 is continuous with the sulcus sagittalis. A fourth groove or (more often) ridge extends to the 

 foramen magnum and receives the sinus occipitalis. The anterior surface presents variably 

 marked juga cerebralia and cerebellaria and impressiones digitatae. 



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