148 HEAD AND NECK 



vertebrae; there it ends by dividing into its two terminal 

 branches the internal and the external carotid arteries. 



Superficial Relations. Above the level of the anterior 

 belly of the omo-hyoid the common carotid artery is covered 

 by the skin, the superficial fascia and the platysma, the deep 

 fascia and the anterior margin of the sterno-mastoid. It is 

 crossed, immediately above the omo-hyoid, by the sterno- 

 mastoid branch of the superior thyreoid artery, and, at a higher 

 level, by the superior thyreoid vein ; and it is overlapped by 

 the anterior margin of the internal jugular vein. In the 

 lower part of its extent it lies more deeply : its superficial 

 relations are, the skin and superficial fascia, the deep fascia 



Thyreo-hyoid ligament M. sternohyoideus 



Plica vocalis ^^g|^ . "<5^^ M - thyreohyoideus 

 Processus vocalis ^^^^i^l^^^^^^^^ Thyreoid cartilage 

 Arytaenoid cartilage^^^^^B^^^^^^ M. omohyoideus 



, 



Common carotid 



Carotid sheath * ^ITlliif^^^^lMHn^* '^^WT Internal jugular 



Vagus" 



Scalenus anterior Sympathetic trunk 



M. longus colli Vertebral artery 



FIG. 53. Transverse section through the Neck at the level of upper 

 part of Thyreoid Cartilage. 



and the sterno-mastoid; the anterior jugular vein, crossing 

 transversely, deep to the sterno-mastoid and above the upper 

 border of the clavicle ; the omo-hyoid, the sterno-hyoid, and 

 the sterno - thyreoid muscles. Deep to the muscles, the 

 branches of the ansa hypoglossi descend in front of its 

 sheath ; and the middle thyreoid vein crosses it to join the 

 internal jugular vein (Fig. 51). 



Posterior to it lie the transverse processes of the cervical 

 vertebrae and the origins of the longus colli, longus capitis 

 and the scalenus anterior. The sympathetic trunk is directly 

 behind it, and the vagus is postero-lateral to it. The inferior 

 thyreoid artery crosses posterior to it, at the level of the cricoid 

 cartilage ; and the vertebral artery lies between it and the 

 transverse process of the seventh cervical vertebra. On the 



