D. V. jugularis externa ([Fig. 131]; [Fig. 65], 5, [page 109]).—The external jugular vein comes from the head and face. It is formed by the junction of the anterior ([Fig. 131], c) and posterior (b) facial veins near the ventral border of the sternomastoid muscle. It passes thence obliquely across the sternomastoid to the triangular interval between it and the clavotrapezius. In the interval it receives a small branch which accompanies the branch of the transversa scapulæ artery to the clavobrachialis muscle, receives next the common trunk of the vena cephalica and transversa scapulæ, and opposite the cranial end of the manubrium receives the internal jugular vein ([Fig. 129], l). It then unites with the subclavian to form the innominate vein. Near the point where it receives the internal jugular the external jugular vein receives the thoracic duct ([Fig. 118], 5).
Branches of the external jugular:
a. V. transversa scapulæ.—This follows the course of the artery of the same name. One of its branches receives one of the two terminal divisions of the vena cephalica (q. v.). In many cases veins which correspond to branches of the transversa scapulæ artery enter the external jugular separately (as shown in [Fig. 118], x and y).
b. V. cervicalis ascendens.—A small branch which follows the corresponding branch of the thyrocervical axis.
c. V. jugularis interna ([Fig. 118], 2; [Fig. 119], [page 284]).—The internal jugular vein varies much in size and in the place where it joins the external jugular. The point of junction is usually at about the level of the first rib, but may be much farther craniad. It arises on the ventral side of the basal portion of the occipital by the junction of a number of veins which are described below. The internal jugular passes caudad in the neck region at the side of the trachea, in company with the common carotid artery and the vagus and sympathetic nerves. In this region it receives branches which accompany the branches of the common carotid artery.
The veins which by their union form the internal jugular vein are the following:
(1) One or two veins from the venous sinuses of the brain, leaving the cranial cavity by the jugular foramen. These are [described] in the account of the veins of the brain.
(2) A large communicating branch from the posterior facial.
(3) The vena occipitalis, a large branch coming from the vertebral column (which it leaves by the atlantal foramen) and from the back of the head.
d. V. facialis anterior ([Fig. 131], c).—The anterior facial vein collects the blood from the face, the tongue, and adjacent parts; it joins the posterior facial (b) caudad of the angle of the jaw to form the external jugular vein.