1406 



VENOUS SYSTEM. 



niastoid muscle, beneath which it passes, a 

 little above the clavicle, to join the internal 

 jugular vein, close to the junction of the latter 

 with the subclavian vein. 



The anterior jugular vein, in its course down 

 the neck, communicates freely with the inter- 

 nal and external jugular veins, and sometimes 

 terminates by opening into the latter. 



It receives branches from the larynx, and 

 sometimes from the thyroid gland. 



Not unfrequently the veins of opposite sides 

 are connected by a transverse branch, which 

 crosses the trachea immediately above the 

 sternum, and receives the terminations of some 

 of the inferior thyroid veins, and of one or 

 two subcutaneous veins from the thorax. 



Internal jugular vein. The blood which 

 has circulated through the brain and sinuses 

 of the dura mater, is returned by the great 

 lateral sinus to the internal jugular vein, 

 which extends from the posterior part of the 

 foramen lacerum posterius, to the root of the 

 neck, where on each side it forms the vena in- 

 nominata, by its union with the subclavian vein. 



Its direction is strictly vertical. 



At its commencement this vein presents an 

 oval dilatation (sinus, or gulph of the internal 

 jugular vein), which is lodged in the jugular 

 fossa, and into which the inferior petrosal sinus 

 of the dura mater opens. The internal ju- 

 gular vein is placed posterior, and external, to 

 the internal carotid artery, (the lingual, glosso- 

 pharyngeal, and pneumogastric nerves inter- 

 vening,) and rests upon the anterior surface of 

 the rectus capitis lateralis muscle ; but as the 

 vein is traced downwards, it will be found, a 

 little below the base of the skull, to lie parallel 

 with, and to the outer side of, the internal 

 carotid ; the spinal accessory nerve here de- 

 scends upon the anterior surface of the vein. 

 Subsequently, the internal jugular vein enters 

 the sheath of the common carotid artery, 

 along with the vagus nerve, and preserves the 

 same relative position to that great vessel as 

 it did to its internal branch. At the root of 

 the neck the vein of the right side intersects, 

 at right angles, the front of the first stage of 

 the subclavian artery ; on the left side, the 

 vein, whilst it is anterior, is at the same time 

 parallel, to the thoracic stages of the sub- 

 clavian and carotid arteries. 



Collateral branches of the internal jugular 

 vein. Opposite the cornu of the os hyoides, the 

 internal jugular vein is joined by (a) the facial 

 vein, and sometimes by (b) a large communi- 

 cating branch from the temporo-maxillary vein, 

 by which its size is sensibly augmented ; above 

 the os hyoides, it receives (c) the pharyngcal 

 vein, derived from a venous plexus on the sides 

 and back of the phanynx; (d), the proper lin- 

 gual veins, two in number, " venae comites " 

 of the lingual artery, the course of which they 

 accurately follow : the lingual veins, as has 

 been already stated, sometimes form a trunk 

 of considerable size, by uniting with the facial 

 vein * ; and (e), the occipital vein, which has 



* In considering the distribution of the veins of 

 the tongue, it may be observed that there are two 



been described in the preceding page. Below 

 the level of the os hyoides, the internal jugular 

 vein receives (f) a laryngeal branch, which 

 escapes from the larynx through an opening 

 in the thyro-hyoid membrane ; (g), the stipe- 

 rior thyroid veins, " venae comites " of the 

 superior thyroid artery, and which emanate 

 from the superficial and upper portions of the 

 thyroid gland : these occasionally terminate 

 in the anterior jugular vein, or in the common 

 trunk of the facial and lingual veins when it is 

 present ; and (h) the middle thyroid veins, 

 which pass out from the lower part of the 

 lateral lobe of the gland, and join the most 

 inferior portion of the internal jugular vein. 



The vertebral vein, The vertebral vein 

 arises by muscular branches, which are 

 deeply placed at the base of the skull, in the 

 vicinity of the foramen magnum, .and first 

 exists as a distinct trunk in the foramen of 

 the transverse process of the atlas, where it is 

 joined by two communicating branches, one 

 of which passes through the posterior condy- 

 loid foramen, and opens into the great lateral 

 sinus, whilst the other is derived from the oc- 

 cipital vein. 



The course and relations of the vertebral 

 vein, from this to its tern;ination, are iden- 

 tical with those of the cervical stage of its 

 corresponding artery, which it accompanies 

 through the foramina in the transverse pro- 

 cesses of the cervical vertebrae. On issuing 

 from the foramen of the sixth vertebra, it is 

 joined by the veins which accompany the ar- 

 teria cervicalis profunda and the arteria cer- 

 vicalis superficialis. Lastly, the vertebral vein 

 usually passes behind the subclavian artery on 

 the right side, and in front of that vessel, on 

 the left side, to terminate in the vena inno- 

 minata. Sometimes, though rarely, the ver- 

 tebral ends in the internal jugular vein.* 



The vertebral veins anastomose very freely 

 with the spinal veins, as well with those which 

 are within the spinal canal, as with those 

 which are external to the vertebrae, by means 

 of small branches which enter the foramina, 

 by which the cervical spinal nerves issue. 



3. Veins of the tipper extremity. These 

 veins are arranged in two series, a superficial and 

 a deep; both of which are provided with valves, 

 but the deep veins the most abundantly. 



Superficial Veins. In the fore-arm and 

 hand these veins are distributed with great 

 minuteness in the subcutaneous areolar tissue, 

 and anastomose freely with one another ; 

 but their larger branches chiefly occupy the 

 radial and ulnar (the lateral) aspects of the 

 fore- arm. 



The radial or external superficial veins ema- 

 nate from numerous venules on the thumb 

 and dorsum of the fore-finger, and are joined 



superficial or submucoits veins, (the ranine vein, and 

 the satellite vein of the gustatory nerve) correspond- 

 ing to the subcutaneous veins in the limbs, by which 

 the blood is returned when the deep veins (proper 

 lingual) are compressed during the contractions of 

 the organ. 



* Vide Art. SUBCLAVIAN ARTEKY, Vol. IV. 

 pp. 815. and 822. 



