456 



Veins of the Trunk. 



V. vertebralis 



V. iliaoa 

 communis 



. iliolumbalis 



\'. sacralis 

 media 



495. Vena azygos, 



viewed from in front. 



(The diaphrafj^m and the lumbar 

 nuiseles have been removed.) 



y. azyg'OS, unpaired, begins 

 as a continuation of the v. kim- 

 balis ascendens dextra (seep. 4 GO), 

 between the right erus niediale and 

 cms intermedium of the diaphragm, 

 ascends in the spatium mediastinale 

 posterius on the right side of the 

 vel-tebral bodies, and in its course 

 V. hemiazygos lies in front of the aa. intercostales, 

 to the right of the aorta thora- 

 calis and of the ductus thoracicus 

 and behind the oesophagus. At 

 the level of the 5tb or 4* tho- 

 racic vertebra it bends forward 

 over the root of the right lung 

 and opens into the v. cava supe- 

 rior (see also Figs. 427 and 628). 

 In this latter portion of its course 

 it usually possesses valves, which, 

 however, are not efficient. It re- 

 ceives the nine lowermost vv. inter- 

 costales of the right side, as 

 well as tlie vv. oesophageae, 

 vv. broncJiiale.<: posterioi-es and 

 vv. mediastinales posteriores (from 

 the corresponding organs) (not 

 illustrated), besides the V. hemi- 

 azygos. The latter (see also Fig. 

 629) begins, unpaired, between 

 the left crus mediale and cms 

 intermedium of the diaphragm as the 

 continuation of the v. lumbalis ascen- 

 dens sinistra , but is also connected 

 with the v. renalis sinistra. Devoid 

 of valves, it extends upward, behind 

 the aorta thoracalis, on the left side 

 of the bodies of the vertebrae, re- 

 ceives several vv. intercostales sinistrae, 

 vv. oesophageae and vv. mediastinales 

 posteriores, and bends to the right in 

 front of one of the inferior or middle 

 thoracic vertebrae behind the ductus 

 thoracicus to go to the v. azygos. The 

 intercostal veins, next higher up on 

 the left side, empty into a V. liemi- 

 azygos accessoria, which goes down- 

 ward on the left side of the thoracic 

 spine and empties either into the 

 V. hemiazygos or directly into the 

 V. azj'gos. The 3 4 upper intercostal 

 veins open on each side into a v. inter- 

 costalis snprema, which on the right 

 side usually opens into the v. azygos 

 (supplied with valves), on the left side 

 into the v. hemiazygos, but in addition 

 also conmiunicates above on each side 

 with the V. anonvma. 



_V. anonyiua 

 sinistra 



_V. intereostalis 

 suprema 

 sinistra 



_V. cava 



superior 

 .V. intereostalis 



suprema dextra 



accessoria 



^_J V. hemiazygos 



~~~V. bronchialis 

 posterior 



_ _V. azygos 

 V. intereostalis 



.V. hemiazygos 



-V. oesophagea 



V. 



mediastinalis 

 posterior 



"V. renalis 

 sinistra 



"V. cava 

 inferior 



V. 



lumbalis 



III 



V. lumbalis 

 ascendens 



