598 THE ARTERIES 



On its outer side it is in contact in its upper third with the extensor longus 

 digitorum muscle; in its middle third with the extensor proprius hallucis; but, as 

 this nmscle crosses to the inner side of the artery, the vessel usually for a very short 

 part of its course comes again into contact with the extensor longus digitorum. At 

 the upper and lower thirds of its course on the front of the leg the artery has the 

 anterior tibial nerve to its outer side. 



In front the artery is covered by the skin, superficial and deep fascia. In its 

 upper two-thirds it is deeply placed in the cellular interval between the tibialis 

 anticus on the inner side, and the extensor longus digitorum and extensor proprius 

 hallucis on its outer side; and in its lower third it is crossed from without inwards 

 by the tendon of the extensor proprius hallucis, and lies beneath the anterior 

 annular ligament of the ankle-joint. The anterior tibial nerve is usually in front 

 of the artery in the middle third of the leg. 



The branches of the anterior tibial artery are: — (1) The posterior tibial 

 recurrent; (2) the superior fibular; (3 ) the anterior tibial recurrent; (4) the mus- 

 cular; (5) the internal malleolar; and (6) the external malleolar. 



(1) The posterior tibial recurrent is occasionally absent. It ascends between 

 the popliteus muscle and the posterior ligament of the knee-joint supplying these 

 structures and the superior tibio-fibular joint. It anastomoses with the inferior 

 external articular branch of the popliteal, and, to a less extent with the inferior 

 internal articular branch. 



(2) The superior fibular is a branch of small size which arises from the main 

 trunk just before it passes through the interosseous space. It winds round the 

 neck of the fibula, pierces the attachment of the soleus and is distributed to that 

 muscle and to the skin. 



(3) The anterior tibial recurrent is given off from the anterior tibial artery 

 immediately after that vessel has passed through the interosseous membrane. It 

 winds tortuously through the substance of the tibialis anticus muscle, over the 

 outer tuberosity of the tibia close to the bone; and, perforating the deep fascia, 

 ramifies on the lower and outer part of the capsule of the knee-joint. It anas- 

 tomoses with the inferior and superior external articular branches of the popliteal, 

 with the descending branch of the external circumflex, and somewhat less freely 

 with the internal articular branches of the popliteal and with the anastomotica 

 magna. It gives off small branches to the tibialis anticus, the extensor longus 

 digitorum, the knee-joint, and the contiguous fascia and skin. It forms one of the 

 collateral channels by which the blood is carried to the limb below in obstruc- 

 tion of the popliteal artery (tig. 376). 



(4) The muscular branches, some ten or twelve in number, arise irregularly 

 from either side of the artery as it courses down the limb, and supply the con- 

 tiguous muscles. 



(5) The internal malleolar, the smaller of the two malleolar branches, arises 

 from the loAver part of the anterior tibial artery a little higher than the external, 

 usually about the spot where the tendon of the extensor longus hallucis crosses the 

 anterior tibial artery. It winds inwards over the internal malleolus, passing 

 beneath the tibialis anticus, and forms an internal malleolar plexus or rete about 

 the inner ankle over the loAver end of the tibia by anastomosing with branches from 

 the posterior tibial, internal plantar, and internal calcanean arteries. 



(6) The external malleolar, larger than the internal, arises from the outer 

 side of the anterior tibial artery, usually on a lower level than the internal 

 malleolar. It winds in an outward and downward direction round the external 

 malleolus, passing beneath the extensor longus digitorum and peroneus tertius. and 

 forms the external malleolar plexus or rete l>v anastomosing with the anterior 

 peroneal, the termination of the peroneal, the external plantar, and the external 

 tarsal branch of the dorsalis pedis (fig. 381). 



The anastomosis between the external malleolar and anterior peroneal is some- 

 times of considerable size, supplying the blood to the dorsal artery of the foot: the 

 anterior tibial, then much reduced in size, usually ends at the spot where the 

 external malleolar is usually given off. 



