MUSCLES AND FASCIA OF THE NECK 381 



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

 small, covered by soft skin, and often by a considerable layer of fat, so that their outline is con- 

 cealed, but they serve to round off and smooth prominent borders and to fill up what would be 

 otherwise unsightly angular depressions. Thus, t^e Orbicularis palpebrarum rounds off the 

 prominent margin of the orbit, and the Pyramidalis nasi fills in the sharp depression beneath 

 the glabella, and thus softens and tones down the abrupt depression which is seen on the un- 

 clothed bone, In like manner, the labial muscles, converging to the lips and assisted by the 

 superimposed fat, fill in the sunken hollow of the lower part of the face. Although the muscles 

 of the face are usually described as arising from the bones and inserted into the nose, lips, and 

 corners of the mouth, they have fibres inserted into the skin of the face along their whole extent, 

 so that almost every point of the skin of the face has its muscular fibre to move it; hence it is 

 that when in action the facial muscles produce alterations in the skin-surface, giving rise to the 

 formation of various folds or wrinkles, or otherwise altering the relative position of the parts, 

 so as to produce the varied expressions with which the face is endowed; hence these muscles 

 are termed the muscles of expression. 1 The only two muscles in this region which greatly influence 

 surface form are the Masseter and the Temporal. The Masseter is a quadrilateral muscle, 

 which imparts fulness to the hinder part of the cheek. When the muscle is firmly contracted, as 

 when the teeth are clenched, its outline is plainly visible; the anterior border forms a prominent 

 vertical ridge, behind w T hich is a considerable fulness, especially marked at the lower part of the 

 muscle; this fulness is entirely lost when the mouth is opened and the muscle no longer in a 

 state of contraction. The Temporal muscle is fan-shaped, and fills the temporal fossa, sub- 

 stituting for it a somew 7 hat convex form, the anterior part of which, on account of the absence 

 of hair over the temple, is more marked than the posterior, and stands out in strong relief when 

 the muscle is in a state of contraction. 



MUSCLES AND FASCLffi OF THE NECK. 



The muscles of the neck may be arranged into groups corresponding with the 

 region in which they are situated. 

 These groups are nine in number: 



1. Superficial Cervical Region. 5. Pharyngeal Region. 



2. Infrahyoid Region. 6. Palatal Region. 



3. Suprahyoid Region. 7. Anterior Vertebral Region. 



4. Lingual Region. 8. Lateral Vertebral Region. 



9. Muscles of the Larynx. 



The muscles contained in each of these groups are the following: 

 1. Superficial Region. 4. Lingual Region. 



Platysma. 



Sternomastoid. 



/ 



2. Infrahyoid Region. 



Sternohyoid. 

 Sternothroid. 



Geniohyoglossus. 



Hyoglossus. 



Chondroglossus. 



Styloglossus. 



Palatoglossus. 



Superior lingual. 



. * .T . Inferior lingual. 



Omoh oid ? Transverse lingual. 



* H- i I Vertical lingual. 



3. Suprahyoid Region. 5 ^nde, Q/ ^ pharynXm 



Inferior 





