THE POPLITEAL ARTERY. 831 



7. The Anastomotica Magna. — The anastomotica magna (a. genu supremaj 

 (Fig. 733) arises from the femoral, just before it passes through the adductor magnus. 

 It passes downward a short distance in front of the adductor magnus and divides into 

 two branches, a superficial and a deep. 



Branches. — {a) The superficial branch (ramus saphenus) follows the course of the long 

 saphenous nerve and, perforating with it the crural fascia, is supplied to the integument over the 

 inner side of the knee and the upper portion of the leg. It anastomoses with the inferior in- 

 ternal articular branch of the popliteal, then entering into the formation of the circumpatellar 

 anastomosis 



{b) The deep branch (ramus musculo-articularis) enters the substance of the vastus internus 

 and passes downward to take part in the formation of the circumpatellar plexus, also sending 

 branches to the capsule of the knee-joint. 



Variations. — The anastomotica magna is occasionally given off from the upper portion of the 

 popliteal artery. Occasionally it is continued some distance down the leg with the long saphe- 

 nous nerve, representing in such cases more perfectly the original saphenous artery (page 849) ; 

 or this vessel may be indicated by a series of anastomoses which accompany the nerve and vein 

 and begin with the superficial branch of the anastomotica. 



Anastomoses of the Femoral Artery. — In the case of obliteration of the 

 external iliac artery, blood may reach the femoral by means of the anastomoses of the 

 iliac arteries already noted (pa.ge 821), and, in addition, byway of the anastomoses 

 between the superficial and deep epigastrics and between the superficial circumflex 

 iliac artery and the deep vessel of the same name and the gluteal. The anastomoses 

 between the external and internal pudics would also assist. 



If the obliteration of the femoral artery be above the origin of the profunda 

 femoris, a collateral circulation may be established by the union of the branches of that 

 vessel with the sciatic in the crucial anastomosis and also by the communication exist- 

 ing between the external circumflex and the gluteal and the deep circumflex iliac. 



If the obliteration be below the origin of the profunda, circulation will be main- 

 tained through the anastomoses around the knee-joint, in which the descending 

 branch of the external circumflex and the terminal portion of the profunda, on the 

 one hand, and the anastomotica magna, on the other, participate. 



THE POPLITEAL ARTERY. 



The popliteal artery (a. poplitea) (Fig, 736) is the continuation of the femoral, 

 and extends from the point where the latter pierces the adductor magnus to the lower 

 border of the popliteus muscle, where it divides into the an .erior and posterior tibial 

 arteries. Its course is at first downward and slightly outward, but it soon becomes 

 almost vertical, corresponding practically with the long axis of the popliteal space. 



Relations. — Anteriorly^ the popliteal artery is in relation «to the posterior sur- 

 face of the lower part of the femur, from which it is separated, however, by a layer 

 of adipose tissue. Lower down it rests upon the posterior ligament of the knee-joint, 

 and still lower upon the fascia covering the posterior surface of the popliteus muscle. 

 Posteriorly, it is somewhat overlapped in the upper part of its course by the border of 

 the semimembranosus, and below by the inner head of the gastrocnemius. In its pas- 

 sage through the popliteal space, however, it is covered only by the integument and 

 fasciae, beneath which is a considerable amount of fatty tissue. About the middle of its 

 course it is crossed obliquely from without inward by the internal popliteal nerve, and 

 throughout its entire length it has resting upon and firmly adherent to it the popliteal 

 vein, which lies, however, slightly to its outer side above and to its inner side below. 

 Internally, it is in relation from above downward with the semimembranosus, the 

 internal condyle of the femur, the internal popliteal nerve, and the inner head of the 

 gastrocnemius, and externally with the internal popliteal nerve, the external condyle 

 of the femur, the outer head of the gastrocnemius, and the plantaris. 



Branches. — The branches which arise from the popliteal artery are all small 

 and may be arranged in three groups : (i) 7nuscular, (2) articjilar, (3) cutaneotis. 



Variations. — The popliteal artery occasionally divides into the tibial arteries above the 

 upper border of the popliteus muscle, and more rarely the division is delayed until the artery 

 has reached a point almost half-way down the leg. 



