502 



DISSECTION OF THE HEAD. 



Occipito- 

 frontalis. 



Occipital 

 part: origin 

 and ending. 



Frontal 

 part : 



how at- 

 tached. 



Aponeu- 

 rosis : 



its attach- 

 ment, 



and rela- 

 tions. 



Prolonga- 

 tion to ear. 



Use of an- 

 terior and 



pOSt(!l 



belly. 



terior 



Vessels of 

 the scalp. 



former nerve lies by the side of the artery, and the latter about 

 midway between this vessel and the ear. 



The OCCIPITO-FRONTALIS MUSCLE (fig. 185, ', 4 ) covers the greater 

 part of the vault of the skull, and consists of anterior and posterior 

 fleshy parts with an intervening aponeurotic tendon. 



The posterior part, or the occipitalis ( 4 ), arises from the outer half 

 or more of the upper curved line of the occipital bone, and from 

 the mastoid portion of the temporal bone. The fibres are about 

 one inch and a half in length, and ascend to the aponeurosis. 



The anterior part, or the frontalis (*), forms a thin layer 

 which covers about the lower two-thirds of the frontal bone. Its 

 fibres are paler than those of the occipital part, and spring from 

 the aponeurosis some distance below the line of the coronal suture. 

 They descend to the eyebrow and root of the nose, where they 

 interlace with the fibres of the orbicularis palpebrarum, corrugator 

 supercilii and pyramidalis nasi muscles (fig. 203, p. 553), and 

 terminate in the subcutaneous tissue. Some fasciculi are frequently 

 attached to the nasal bone internally, and to the external angular 

 process of the frontal bone on the outer side. The right and left 

 muscular portions meet at the lower part of the forehead. 



The tendon of the occipito-frontalis, or the epicranial aponeurosis, 

 covers the upper part of the cranium, and is continuous across the 

 middle line with the like structure of the opposite half of the head. 

 In front, it sends a pointed process downwards for some distance 

 between the two muscular portions ; and behind, it is prolonged 

 between the posterior bellies, to be attached to the occipital bone 

 along the highest curved line. From its lateral margin the upper 

 auricular muscles arise. Superficial to the aponeurosis are the 

 vessels and nerves of the scalp and a small quantity of fat, which 

 is traversed by numerous short fibrous bands uniting it closely 

 to the skin. Its deep surface is connected to the pericranium only 

 by a loose areolar tissue devoid of fat, so that the scalp moves 

 freely over the skull. 



By making a transverse incision through the aponeurosis above 

 the ear and separating it from the pericranium towards the side of 

 the head, it will be seen to be joined by a thin membrane, which 

 springs from the skull along the superior temporal line, and 

 descends, closely united to the deep surface of the attollens aurem 

 muscle, over the temporal fascia to be attached to the pinna of the 

 ear. 



Action. When the anterior belly contracts it raises the eyebrow, 

 smoothing the skin at the root of the nose, and wrinkling trans- 

 versely that of the forehead ; and continuing to contract, it draws 

 forward the scalp. The posterior belly will move the scalp back- 

 wards ; and the bellies acting in succession can carry the hairy 

 scalp forwards and backwards. 



CUTANEOUS ARTERIES. The arteries of the scalp (fig. 186) 

 are furnished by the internal and external carotid trunks, and 

 anastomose freely over the side of the head. Only two small 

 branches, the supraorbital and frontal, come from the internal 



