776 



THE VASCULAR SYSTEMS 



bronchomediastinal trunk; the last named, however, usually opens independently 

 into the junction of the left subclavian and internal jugular veins. 



Structure. The thoracic duct is composed of three coats, which differ in some respects 

 from those of the lymphatic vessels. The internal coat consists of a single layer of flattened 

 endothelial cells; of a subendothelial layer, similar to that found in the arteries; and an elastic 

 fibrous layer, the fibres of which run in a longitudinal direction. Each endothelial cell is shaped 

 like a lance-head and has serrated borders. The middle coat consists of a longitudinal layer 



LONGUS COLLI MUSCLE 



COMMON CAROTID 



ARTERY 



LEFT VAGUS 



NERVE 



VERTEBRAL ARTERY 



VERTEBRAL VEIN 

 THORACIC DUCT 



INTERNAL JUGULAR 

 VEIN 



EXTERNAL JUGULAR 

 VEIN 



ANTERIOR JUGULAR 

 VEIN 



SUBCLAVIAN 

 VEIN 



FIG. 554. The bend of the thoracic duct at its termination in the subclavian vein. (Poirier and Charpy.) 



of white connective tissue with elastic fibres, external to which are several laminae of muscle 

 tissue, the fibres of which are for the most part disposed transversely, but some are oblique or 

 longitudinal. The muscle fibres are intermixed with elastic fibres. The external coat is 

 composed of areolar tissue, with elastic fibres and isolated fasciculi of nonstriated muscle fibres. 



The Right Lymphatic Duct (Ductus Lymphaticus Dexter) (Figs. 552, 555). 



The right lymphatic duct, about half an inch in length, courses along the inner 

 border of the Scalenus anticus at the root of the neck and terminates in the right 



FIG. 555. Terminal collecting trunks of the right side : a. Jugular trunk 6. Subclavian trunk, c. Broncho- 

 "light lymphatic trunk, e. Node of the internal mammary chain. /. Node of the deep 



medjastinal trunk, d. Right lymphs 

 cervical chain. (Poirier and Charpy.) 



subclavian vein at its angle of junction^svith the right internal jugular vein. The 

 orifice of the right lymphatic duct is guarded by two semilunar valves, which 

 prevent the passage of venous blood into the duct. 



Tributaries. It receives the lymph from the right side of the head and neck 

 through the right jugular trunk; from the right upper extremity through the right 



