186 



PLATYSMA MYOIDES. 



8 Muscles of the Larynx. 

 Crico-thyroideus, 

 Crico-arytsenoideus, posticus, 



Crico-arytsenoideus, lateralis, 



Thyro-arytsenoideus. 



Arytsenoideus. 



Dissection. The dissection of the neck should be commenced by 

 making an incision along the middle line of its fore part from the chin to 

 the sternum, and bounding it superiorly and inferiorly by two transverse 

 incisions ; the superior one being carried along the margin of the lower 

 jaw, and across the mastoid process to the tubercle on the occipital bone, 

 the inferior one along the clavicle to the acromion process. The square 

 flap of integument thus included should be turned back from the entire 

 side of the neck, which brings into view the superficial fascia, and on the 

 removal of a thin layer of superficial fascia the platysma myoides will be 

 exposed. 



The PLATYSMA MYOIDES (irXarus, fwfc si5o<r, broad muscle-like lamella), 

 is a thin plane of muscular fibres, situated between the two layers of the 

 superficial cervical fascia ; it arises from the integument over the pectoralis 

 major and deltoid muscles, and passes obliquely upwards and inwards 

 along the side of the neck to be inserted into the side of the chin, oblique 

 line of the lower jaw, the angle of the mouth, and into the cellular tissue 

 of the face. The most anterior fibres are continuous beneath the chin, 

 with the muscle of the opposite side; the next interlace with the depressor 

 anguli oris, and depressor labii inferioris, and the most posterior fibres are 

 disposed in a transverse direction across the side of the face, arising in the 

 cellular tissue covering the parotid gland, and inserted into the angle of 

 the mouth, constituting the risorius Santorini. The entire muscle is ana- 

 logous to the cutaneous muscle of brutes, the panniculus carnosus. 



Relations. By its external 



Fig. 109* 



surface with the integument, 

 with which it is closely adhe- 

 rent below, but loosely above. 

 By its internal surface, below 

 the clavicle, with the pectoralis 

 major and deltoid ; in the neck, 

 with the external jugular 'vein 

 and deep cervical fascia ; on 

 the face, with the parotid 

 gland, the masseter, the facial 

 artery and vein, the buccinator, 

 the depressor anguli oris, and 

 the depressor labii inferioris. 



On raising the platysma- 

 throughout its whole extent, 

 the s^erno-mastoid is brought 

 into view,. 



The STERNO-CLEIDO-MASTOID 

 is the large oblique muscle of 



*The muscles of the anterior aspect of the neck ; on the left side the superficial mus- 

 cles are seen, and on the right the deep. 1. The posterior belly of the digastricus mus- 

 cle. 2. Its anterior belly. The aponeurotic pulley, through which its tendon is seen 

 passing, is attached to the body of the os hyoides. 3, 4. The stylo-hyoideus muscle, 

 transfixed by the posterior belly of the digastricus. 



0. The mylo-hyoideus. 6. Tho 



