374 VEINS OF THE NECK. 



The Circular sinus (sinus of Ridley) is situated in the sella turcica, 

 surrounding the pituitary gland, and communicating on each side 

 with the cavernous sinus. The posterior segment is larger than the 

 anterior. 



The Superior petrosal sinuses pass obliquely backwards along the 

 attached border of the tentorium, on the upper margin of the petrous 

 portion of the temporal bone, and establish a communication between 

 the cavernous and lateral sinus at each side. They receive one or two 

 cerebral veins from the inferior part of the middle lobes, and a cerebellar 

 vein from the anterior border of the cerebellum. Near the extremity 

 of the petrous bone these sinuses cross the oval aperture which trans- 

 mits the fifth nerve. 



The Transverse sinus (basilar, anterior occipital) passes transversely 

 across the basilar process of the occipital bone, forming a communica- 

 tion between the two inferior petrosal sinuses. Sometimes there are 

 two sinuses in this situation. 



VEINS OF THE NECK. 



The veins of the neck which return the blood from the head are the 



External jugular, 

 Anterior jugular, 

 Internal jugular, 

 Vertebral. 



The External jugular vein is formed by the union of the pos- 

 terior auricular vein with the temporo-maxillary, and commences 

 at the lower border of the parotid gland, in front of the sterno-mastoid 

 muscle. It descends the neck in the direction of a line drawn from the 

 angle of the lower jaw to the middle of the clavicle, crosses the sterno- 

 mastoid, and terminates near the posterior and inferior attachment of 

 that muscle in the subclavian vein. In its course downwards it lies 

 upon the anterior lamella of the deep cervical fascia, which separates 

 it from the sterno-mastoid muscle, and is covered in by the platysma 

 myoides and superficial fascia. At the root of the neck it pierces the 

 deep cervical fascia ; it is accompanied, for the upper half of its 

 course, by the auricularis magnus nerve. The brandies which it re- 

 ceives are the occipital cutaneous and posterior cervical cutaneous, and, 

 near its termination, the supra and posterior scapular. 



The external jugular vein is very variable in size, and is occasionally 

 replaced by two veins. In the parotid gland it receives a large com- 

 municating branch from the internal jugular vein. 



The Anterior jugular vein is a trunk of variable size, which col- 

 lects the blood from the integument and superficial structures on the 

 fore part of the neck. It passes downwards along the anterior border 

 of the sterno-mastoid muscle, and opens into the subclavian vein, near 

 the termination of the external jugular. The two veins communicate 



