

SURFACE ANATOMY OF THE HEAD AND NECK 



1289 



are so thin that the outline of the bone is perceptible beneath them. Those of 

 the face are small, covered by soft skin, and often by a considerable layer of fat, 

 and their outlines are therefore concealed ; they serve, however, to round off and 

 smooth prominent borders, and to fill up what would otherwise be unsightly 

 angular depressions. Thus the Orbicularis oculi rounds off the prominent margin 

 of the orbit, and the Procerus fills in the sharp depression below the glabella. In 

 like manner the labial muscles converging to the lips, and assisted by the super- 

 imposed fat, fill up the sunken hollow of the lower part of the face. When in 

 action the facial muscles produce the various expressions, and in addition throw 

 the skin into numerous folds and wrinkles. The Masseter imparts fulness to the 

 hinder part of the cheek; if firmly contracted, as when the teeth are clenched, its 

 quadrilateral outline is plainly visible; the anterior border forms a prominent 

 vertical ridge, behind which is a considerable fulness especially marked at the 



Svbmaxillary triangl 

 Hyoid bone 



Thyroid cartilage 

 Cricoid cartilage 



Sternocleidomastoide'us 

 Trapezius 



Supraclavicular fossa 



Clavicle 



Infraclavicular fossa 

 Clavicular head j of Slernockidomastoideua 



Sternal head 



Fia. 1194. Anterolateral view of head and neck. 



lower part of the muscle. The Temporalis is fan-shaped and fills the temporal 

 fossa, substituting for the concavity a somewhat convex swelling, the anterior 

 part of which, on account of the absence of hair on the overlying skin, is more 

 marked than the posterior, and stands out in strong relief when the muscle is in 

 action. 



In the neck, the Platysma when contracted throws the skin into oblique ridges 

 parallel with the fasciculi of the muscle. The Sternocleidomastoideus has the most 

 important influence on the surface form of the neck (Figs. 1194, 1195). When the 

 muscle is at rest its anterior border forms an oblique rounded edge ending below in 

 the sharp outline of the sternal head; the posterior border is only distinct for about 

 2 or 3 cm. above the middle of the clavicle. During contraction, the sternal head 

 stands out as a sharply defined ridge, while the clavicular head is flatter and less 

 prominent; between the two heads is a slight depression: the fleshy middle portion 



