126 



HEAD AND NECK 



and medially, some to blend with the orbicularis oris and 

 others to gain attachment to the skin of the lower lip. 



Platysma. Only the upper part of the broad, flat, 

 quadrangular subcutaneous muscle of the neck is at present 

 visible. The posterior fibres ascend over the lower border 

 of the ramus and the posterior part of the lower border of 

 the body of the mandible, and they have already been seen 

 taking part in the formation of the risorius. The anterior 

 fibres gain direct insertion into the anterior part of the lower 



M. quadratus labii superioris 

 caput angulare 



M. quadratus labii 

 superioris caput 

 infraorbitale 



M. caninus 



M. triangularis 



M. quadratus labii inferioris 



FIG. 58. Diagram of the Orbicularis Oris Muscle. 

 The fibres which enter it from the buccinator are not represented. 



border of the body of the mandible. The latter attach- 

 ment is the only bony attachment which the muscle possesses, 

 all its other attachments being either to fascia or to skin. 



Dissection. Cut through the posterior half of the platysma along the 

 lower border of the mandible ; detach the risorius from the fascia on 

 the masseter ; then turn the risorius and the detached part of the platysma 

 towards the angle of the mouth. Whilst doing this be careful to avoid 

 injuring the branches of the vessels and nerves of the face. 



As soon as the platysma and the risorius are reflected search below the level 

 of the ear for branches of the great auricular nerve which ascend over the 

 lower part of the parotid gland. Some of them pierce the parotid and 

 terminate in its substance, others end in the skin of the masseteric region. 



Find the anterior facial vein and the external maxillary artery at the 



