PARIETAL BONE. 



61 



Articulations. With six bones ; two parietal, two temporal, sphenoid 

 and atlas. 



Attachment of Muscles. To thirteen pairs: to the rough surface above 

 the superior curved line, the occipito-frontalis ; to the superior curved 

 line, the trapezius and sterno-raastoid ; to the rough space between the 

 curved lines, complexus, and splenius capitis ; to the space between the 

 inferior curved line and the foramen magnum, the rectus posticus major 

 and minor, and obliquus superior ; to the transverse process, the rectus 

 lateralis ; and to the basilar process, the rectus anticus major and minor, 

 and superior and middle constrictor muscles. 



Fig. 24.* 



PARIETAL BONE. The parietal 

 bone is situated at the side and ver- 

 tex of the skull ; it is quadrilateral in 

 form, and divisible into an external 

 and internal surface, four borders and 

 four angles. The superior border is 

 straight, to articulate with its fellow 

 of the opposite side. The inferior 

 border is arched and thin, to articu- 

 late with the temporal bone. The 

 anterior border is concave, and the 

 posterior somewhat convex. 



External surface. Crossing the 

 bone in a longitudinal direction from 

 the anterior to the posterior border, is an arched line, the temporal ridge, 

 to which the temporal fascia is attached. In the middle of this line, and 

 nearly in the centre of the bone, is the projection called the parietal emi- 

 nence, which marks the centre of ossification. Above the temporal ridge 

 the surface is rou^h, and covered by the aponeurosis of the occipito-fron- 

 talis ; below the ridge the bone is smooth (planum semicirculare), for the 

 attachment of the fleshy fibres of the temporal muscle. Near the superior 

 border of the bone, and at about one-third from its posterior extremity, 

 is the parietal foramen, which transmits a vein to the superior longitudinal 

 sinus. This foramen is often absent. 



Internal surface. The internal table is smooth ; it is marked by nu- 

 merous furrows, which lodge the ramifications of the arteria meningea 

 media, and by digital fossse which correspond with the convolutions of 

 the brain. Along the upper border is part of a shallow groove, completed 

 by the opposite parietal bone, which serves to contain the superior longitu- 

 dinal sinus. Some slight pits are also observable near this groove, which 

 lodge the glandules Pacchioni. 



The anterior inferior angle is thin and lengthened, and articulates with 

 the greater wing of the sphenoid bone. Upon its inner surface it is 

 deeply channelled by a groove for the trunk of the arteria meningea 

 media. This groove is frequently converted into a canal. The posterior 



* The external surface of the left parietal bone. 1. The superior or sagittal border. 

 2. The inferior or squamous border. 3. The anterior or coronal border. 4. The poste- 

 rior or lambdoidal border. 5. The temporal ridge ; the figure is situated immediately 

 in front of the parietal eminence. 6. The parietal foramen, unusually large in the bona 

 from which this figure was drawn. 7. The anterior inferior angle. 8. The posterior 

 inferior angle. 



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