



THE SUPERFICIAL VEINS OF THE LOWER EXTREMITY 669 



channels in the substance of the bones, similar in every respect to those found in 

 the diploe of the cranial bones. They communicate through small openings on the 

 front and sides of the bodies of the vertebrae with the anterior external vertebral 

 plexuses, and converge behind to the principal canal, which is sometimes double 

 toward its posterior part, and open by valved orifices into the transverse branches 

 which unite the anterior internal vertebral plexuses. They become greatly enlarged 

 in advanced age. 



The intervertebral veins (w. intervertebrales) accompany the spinal nerves 

 through the intervertebral foramina; they receive the veins from the medulla 

 spinalis, drain the internal and external vertebral plexuses and end in the vertebral, 

 intercostal, lumbar, and lateral sacral veins, their orifices being provided with 

 valves. 



The veins of the medulla spinalis (w. spinales; wins of the spinal cord] are 

 situated in the pia mater and form a minute, tortuous, venous plexus. They 

 emerge chiefly from the median fissures of the medulla spinalis and are largest in 

 . the lumbar region. In this plexus there are (1) two median longitudinal veins, 

 one in front of the anterior fissure, and the other behind the posterior sulcus of the 

 cord, and (2) four lateral longitudinal veins which run behind the nerve roots. 

 They end in the intervertebral veins. Near the base of the skull they unite, and 

 form two or three small trunks, which communicate with the vertebral veins, 

 and then end in the inferior cerebellar veins, or in the inferior petrosal sinuses. 



THE VEINS OF THE LOWER EXTREMITY, ABDOMEN, AND PELVIS. 



The veins of the lower extremity are subdivided, like those of the upper, into 

 two sets, superficial and deep ; the superficial veins are placed beneath the integument 

 between the two layers of superficial fascia; the deep veins accompany the arteries. 

 Both sets of veins are provided with valves, which are more numerous in the deep 

 than in the superficial set. Valves are also more numerous in the veins of the 

 lower than in those of the upper limb. 



The Superficial Veins of the Lower Extremity. 



The superficial veins of the lower extremity are the great and small saphenous 

 veins and their tributaries. 



On the dorsum of the foot the dorsal digital veins receive, in the clefts between the 

 toes, the intercapitular veins from the plantar cutaneous venous arch and join to 

 form short common digital veins which unite across the distal ends of the metatarsal 

 bones in a dorsal venous arch. Proximal to this arch is an irregular venous net- 

 work which receives tributaries from the deep veins and is joined at the sides of the 

 foot by a medial and a lateral marginal vein, formed mainly by the union of branches 

 from the superficial parts of the sole of the foot. 



On the sole of the foot the superficial veins form a plantar cutaneous venous arch 

 which extends across the roots of the toes and opens at the sides of the foot into 

 the medial and lateral marginal veins. Proximal to this arch is a plantar cutaneous 

 venous net- work which is especially dense in the fat beneath the heel ; this net-\vork 

 communicates with the cutaneous venous arch and w r ith the deep veins, but is 

 chiefly drained into the medial and lateral marginal veins. 



The great saphenous vein (v. saphena magna; internal or long saphenous vein) 

 (Fig. 581), the longest vein in the body, begins in the medial marginal vein of the 

 dorsum of the foot and ends in the femoral vein about 3 cm. below the inguinal 

 ligament. It ascends in front of the tibial malleolus and along the medial side of 

 the leg in relation with the saphenous nerve. It runs upward behind the medial 





