THE ANTERIOR TIBIA L ARTERY. 641 



of the femur and knee-joint, and forms an anastomotic arch across the bone with 

 the anastomotica magna and the inferior internal articular arteries. 



The azygos articular is a small branch arising from the popliteal artery oppo- 

 site the bend of the knee-joint. It pierces the posterior ligament, and supplies 

 the ligaments and synovial membrane in the interior of the articulation. 



The inferior articular arteries, two in number, arise from the popliteal beneath 

 the Gastrocnemius. and wind round the head of the tibia below the joint. The 

 nal one passes below the inner tuberosity. beneath the internal lateral lig- 

 ament, at the anterior border of which it ascends to the front and inner side of 

 the joint, to supply the head of the tibia and the articulation of the knee, anasto- 

 mosing with the inferior external articular and superior internal articular arteries. 

 The txt>rnal one passes outward above the head of the fibula, to the front of the 

 knee-joint, passing in its course beneath the outer head of the Gastrocnemius, 

 the external lateral ligament, and the tendon of the Biceps muscle, and divides 

 into branches which anastomose with the inferior internal articular artery, the 

 superior external articular artery, and the anterior recurrent branch of the 

 anterior tibial. 



Circumpatellar Anastomosis. Around and above the patella, and on the con- 

 tiguous ends of the femur and tibia, is a large network of vessels, forming a 

 superficial and deep plexus from which numerous offsets proceed into the interior 

 of the joint. The arteries from which this plexus is formed are the two internal 

 and two external articular branches of the popliteal, the anastomotica magna, the 

 terminal branch of the profunda, the descending branch from the external cir- 

 cumflex, and the anterior recurrent branch of the anterior tibial. 



The Anterior Tibial Artery (Fig. 378). 



The anterior tibial artery commences at the bifurcation of the popliteal at the 

 lower border of the Popliteus muscle, passes forward between the two heads of 

 the Tibialis posticus. and through the large oval aperture above the upper border 

 of the interosseous membrane to the deep part of the front of the leg : it then 

 descends on the anterior surface of the interosseous membrane, gradually 

 approaching the tibia : and at the lower part of the leg lies on this bone, and 

 then on the anterior ligament of the ankle to the bend of the ankle-joint, where 

 it lies more superficially, and becomes the dorsalis pedis. 



Relations. In the upper two-thirds of its extent it rests upon the interosseous 

 membrane, to which it is connected by delicate fibrous arches thrown across it ; 

 in the lower third, upon the front of the tibia and the anterior ligament of the 

 ankle-joint. In the upper third of its course it lies between the Tibialis anticus 

 and Extensor longus digitorum ; in the middle third, between the Tibialis anticus 

 and Extensor proprius hallucis. At the bend of the ankle it is crossed by the 

 tendon of the Extensor proprius hallucis. and lies between it and the innermost 

 tendon of the Extensor longus digitorum. It is covered, in the upper two-thirds 

 of its course, by the muscles which lie on either side of it and by the deep fascia ; 

 in the lower third, by the integument, anterior annular ligament, and fascia. 



The anterior tibial artery is accompanied by two veins (venae comites), which 

 lie one on each side of the artery ; the anterior tibial nerve lies at first to its outer 

 side, and about the middle of the leg is placed superficial to it ; at the lower part 

 of the artery the nerve is generally again on the outer side. 



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