648 THE BLOOD-VASCULAR SYSTEM 



usually receives a considerable proportion of the blood returning from the temporal and ptery- 

 goid regions. 



(d) The posterior external jugular vein (fig. 512) descends from the upper and back part 

 of the neck, receiving small tributaries from the superficial structures and muscles. At times it 

 communicates with the occipital, or may appear as a continuation of that vein. It opens into 

 the external jugular as the latter vein is leaving the sterno-mastoid muscle. 



(e) The transverse scapular vein [v. transversa scapulae] corresponds to the transverse 

 scapular (suprascapular) artery. If double, these venae comitantes usually form one trunk 

 before they open into the external jugular vein. They contain well-marked valves. 



(/) The anterior jugular vein [v. jugularis anterior] begins below the chin by communicating 

 with the mental, submental, inferior labial, and inferior hyoid veins. It descends a little 

 lateral to the middle line, receiving branches from the superficial structures at the front and 

 side of the neck, and occasionally a branch from the larynx and thyreoid body. Just above 

 the clavicle it turns laterally, and, piercing the fascia, passes beneath the sterno-mastoid 

 muscle and opens into the external jugular vein just before the latter joins the subclavian; at 

 times it opens into the subclavian vein itself. In its course down the neck it communicates 

 with the external jugular; and, as it turns laterally beneath the sterno-mastoid, sends a branch 

 across the trachea, between the layers of cervical fascia, to join the anterior jugular of the 

 opposite side. This communicating vein, the jugular venous arch [arcus venosus juguli], 

 may open directly into the external jugular or into the internal jugular vein; occasionally one 

 or both ends may open into the subclavian or innominate vein. It may be divided in the 

 operation of tracheotomy, and is then often found greatly engorged with blood. Another 

 branch, often of considerable size, courses along the anterior margin of the sterno-mastoid and 

 joins the anterior facial vein. When the anterior jugular vein is large, the external jugular is 

 small, and vice versa. It is usually also of large size when the corresponding vein on the opposite 

 side is absent, as is frequently the case. It contains no valves. 



THE DEEP VEINS OF THE HEAD AND NECK 



The deep veins of the head and neck may be divided into: — (1) the veins of 

 the diploe; (2) the venous sinuses of the dura mater encephah; (3) the veins of 

 the brain; (4) the veins of the nasal cavities; (5) the veins of the ear; (6) the 

 veins of the orbit; (7) the veins of the pharynx and larynx; and (8) the deep veins 

 of the neck. The veins of the diploe terminate partly in the superficial veins 

 already described, partly in the venous sinuses of the cranium, and partly in the 

 deep veins of the neck. The venous sinuses open into the deep veins of the neck. 

 The veins of the brain terminate in the venous sinuses. The veins of the nasal 

 cavities terminate partly in the deep, and to some extent in the superficial veins. 

 The veins of the ear join both the superficial and deep veins and the venous sinuses. 

 The veins of the orbit terminate partly in the superficial veins, but chiefly in the 

 venous sinuses. The veins of the pharynx and larynx enter the deep veins of the 

 neck. 



1. THE VEINS OF THE DIPLOE 



The veins of the diploe [venae diploica?] (fig. 513) are contained in bony chan- 

 nels in the cancellous tissue between the external and internal laminae of the skull. 

 They are of comparatively large size, with very thin and imperfect walls, and form 

 numerous irregular communicating channels. They have no valves. They ter- 

 minate in four or five main and descending channels, which open, some outward 

 through the external cranial lamina into some of the superficial and deep veins of 

 the head and face, and some inward through the internal lamina into the venous 

 sinuses. They are divided into the frontal, anterior temporal, posterior temporal, 

 and occipital. 



The frontal diploic veins arc contained in the anterior part of the frontal bone. They 

 converge anteriorly to a single vein [v. diploica frontalis] which passes downward, perforates the 

 external table tlirough u small aperture in the roof of the supraorbital notch, and terminates in 

 the supraorbital vein. They also communicate with the superior sagittal sinus. 



The anterior temporal |v. diploica tcrnporalis ant.] are contained in the posterior part of 

 the front;d and in the anterior part of the j)arie(al l)one. They pass downward, and end, partly 

 in the deep temporal veins by perforating the greater wing of the sphenoid bone, and partly 

 in the s[)lieno-parietaI sinus. 



The posterior temporal [v. diploica temporahs post.] ramifies in the parietal bone, and, 

 coursing downward to the posterior inferior angle of that bone, passes either through a foramen 

 in its inner table, or tlirongh the mastoid foramen into the transverse sinus. 



The occipital [v. diploica occipitalis] ramifies chiefly in the occipital bone, and opens into 

 the occipit;d vein or into the tran.sver.se sinus. 



The diploic veins freely anastomose with one another in the adult; but in the foetus, before 

 the bones have united, each system of veins is distinct. 



