34 HEAD AND NECK 



The Deep Fascia. The deep fascia forms the superficial 

 boundary or roof of the posterior triangle. It is attached, 

 below, to the upper border of the middle third of the clavicle ; 

 above, to the superior nuchal line of the occipital bone \ 

 anteriorly, it is continuous with the fascia of the sterno-mastoid, 

 and posteriorly, with the fascia of the trapezius. It is pierced 

 by (i) the supra-clavicular branches of the cervical plexus, (2) 

 the external jugular vein, (3) small cutaneous branches of the 

 transverse cervical, transverse scapular (O.T. suprascapular), 

 and occipital arteries, and, occasionally, by the occipital artery 

 itself. It is not a very strong layer, and it is frequently difficult 

 to display it as a continuous sheet. Over the upper part of the 

 triangle it forms a single layer, but below it splits into two 

 lamellae, a superficial and a deep. The superficial layer, which 

 is already displayed, is attached to the upper border of the 

 clavicle from the sterno-mastoid anteriorly to the trapezius 

 posteriorly. It is pierced by the external jugular vein and 

 the supraclavicular nerves. 



Dissection. Trace the supra-clavicular nerves upwards, 

 through the deep fascia, to the posterior border of the sterno- 

 mastoid ; then, pulling them aside, cut through the superficial 

 layer of the deep fascia immediately above the clavicle and along 

 the posterior border of the sterno-mastoid, and turn it upwards. 

 Introduce the handle of the scalpel behind the clavicle and note 

 that it can be passed downwards as far as the posterior border 

 of the lower surface of the bone. Its further progress is barred 

 by the attachment of the second layer of the deep fascia to that 

 border, where it blends with the posterior lamella of the costo- 

 coracoid membrane. Pass the handle of the knife forwards 

 deep to the sterno-mastoid, and note that, without using any 

 great force, it can be pushed medially until it crosses the median 

 plane ; therefore, the space between the two layers of deep fascia 

 in the lower part of the posterior triangle is continuous anteriorly 

 with the space which lies above and posterior to the manubrium 

 sterni, between the first and the second layers of the deep fascia 

 of the anterior part of the neck. Laterally, that space extends 

 as far as the coracoid process, and upwards to a short distance 

 above the posterior belly of the omo-hyoid muscle, which lies 

 a little above the clavicle. Take away the areolar tissue which 

 lies between the two layers of the deep fascia, and expose a 

 further part of the external jugular vein, and the terminal parts 

 of the transverse cervical and the transverse scapular (supra- 

 scapular) veins, as they join the posterior border of the external 

 jugular. Pull the lower part of the external jugular vein 

 backwards and expose the termination of the anterior jugular 

 vein in its anterior border. Dissect carefully behind the clavicle 

 and find the transverse scapular (suprascapular) artery. Trace 

 the second layer of the deep fascia upwards and note that it 

 is continuous with the fascia which surrounds the posterior 



