726 



THE LYMPHATIC SYSTEM 



The Thoracic Duct 



The thoracic duct [ductus thoracicus] (fig. 570), which is the main collecting 

 duct of the lymphatic system, extends from the second lumbar vertebra along 

 the spinal column and course of the aorta to the j unction of the left internal j ugular 

 and subclavian veins. It receives all the lymphatics below the diaphragm, and 

 the deep lymphatics from the dorsal half of the chest wall; and also, when joined, 

 near its cephalic end, by the left broncho-mediastinal, subclavian and jugular 

 trunks, from the remainder of the left half of the body, above the diaphragm. 

 At the caudal end the duct is formed usually by the union of three collecting 

 ducts, one from each of the lumbar groups of nodes, and an unpaired intestinal 



Fig. 570. — The Thoracic Duct. (After Toldt, "Atlas of Human Anatomy," Rebman, 



London and New York.) 



Thoracic duct 

 __^,— / Internal jugular vein 

 Internal jugular vein |^|f 'it*// Left jugular trunk 



Right lymphatic 

 duct 



Jugular trunk 



Subclavian trunk 

 Subclavian vein 

 Right innominate vein 



Azygos vein 



Left subclavian trunk 

 Subclavian vein 



Intercostal lymph-nodes 



Crus of diaphragm 



Lumbar trunks, right and 

 left 



Lumbar lymphatic plexus 



Axillary lymph -nodes 



[""Thoracic duct 



—Hemiazygos vein 



.Cisterna chyli (recepta- 



culum) 



Intestinal trunks 



Lumbar nodes 



trunk. At its origin there is usually a dihitcd portion known as the receptaculum 

 [cisterna chyli]. This usually ends opposite^ the bod}^ of the eleventh thoracic 

 vertebra, and from here on the duct is from 4 to 6 mm. in diameter, until near its 

 termination, where it is again wider. 



In its cadual part, the duct lies dorsal to the aorta in the median line; it passes 

 through the aortic opening in the diaphragm, and then inclines to the right and 

 passes upward to about the fourth, fifth, or sixth, thoracic vertebra, when it 

 bends to the left and passes, continuing upward, over the apex of the left lung 

 and the left subclavian art(;ry, and in front of tiie root of the left vertebral artery 

 and vein, and then curves downward to ojx'ii into the left subclavian vein, close 

 to its junction with the hift internal juguhir. The duct runs in the wall of the 

 vein a short distance before ending. 



Variations. — There is a wide ranso of variation from this usual course. The duct is fre- 

 quently double throughout a part of its course;, the two branc^hos being connected by cross 

 anastomoses, and finally uniting into a single trunk before joining the veins. It may be 



