GREAT VESSELS AND NERVES OF NECK 307 



and posteriorly is the internal jugular vein. On its medial 

 aspect the internal carotid is related to the pharynx, the 

 ascending pharyngeal artery and the levator veli palatini. 



Before leaving this vessel, note that near the base of the 

 skull four nerves appear in the interval between it and the 

 internal jugular vein ; these are the glosso -pharyngeal, the 

 vagus, the accessory, and the hypoglossal. 



Vena Jugularis Interna. The internal jugular vein is the 

 largest venous channel of the neck. It enters the neck through 

 the postero-lateral compartment of the jugular foramen, where 

 it is directly continuous with the transverse sinus of the cranial 

 cavity. From the jugular foramen it proceeds downwards, 

 until it reaches the posterior aspect of the medial end of 

 the clavicle, where it joins the subclavian vein to form the 

 innominate vein. Its commencement in the jugular foramen 

 shows a slight dilatation, termed the bulb, the lumen of which 

 remains at all times patent owing to the connection of its 

 walls to the margins of the foramen. The skull cap should 

 be removed and a probe should be passed from the trans- 

 verse sinus into the internal jugular vein, to demonstrate the 

 continuity of the two channels. 



Relations. At its commencement the internal jugular 

 vein lies postero-lateral to the upper end of the cervical 

 part of the internal carotid artery, from which it is partially 

 separated by the last four cerebral nerves. As it descends 

 it assumes a more directly lateral relationship, first to the 

 internal and then to the common carotid, overlapping each 

 vessel to a slight extent anteriorly ; and it is enclosed with them 

 and the vagus nerve in a common sheath of deep cervical 

 fascia, the nerve lying in its own compartment of the sheath 

 between the arteries medially and the vein laterally, and in a 

 posterior plane. 



The superficial or lateral relations of the vein in the upper 

 part of its extent are the styloid process, with the stylo- 

 pharyngeus and stylo-hyoid muscles, -and the posterior belly 

 of the digastric, which separate it from the upper part of the 

 postero-medial surface of the parotid gland. In this part 

 of its extent it is crossed superficially, along the upper border 

 of the posterior belly of the digastric, by the posterior 

 auricular artery, and at the lower border of the digastric 

 by the accessory nerve, passing downwards and posteriorly, 

 and by the occipital artery passing upwards and posteriorly 



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