444 POSTERIOR TIBIAL ARTERY. 



branches, especially from the upper and external branch. There are sometimes several 

 small middle articular branches. 



POSTERIOR TIBIAL ARTERY. 



The posterior tibial artery is situated along the back part of the leg, 

 between the superficial and deep layers of muscles, and is firmly bound 

 down to the deep muscles by the fascia which covers them. It eKtends 

 from the lower border of the popliteus muscle, where it is continuous with 

 the popliteal artery, down to the inner side of the calcaneum, where it 

 terminates beneath the origin of the abductor pollicis muscle by dividing 

 into the external and internal plantar arteries. 



Placed at its origin opposite the interval between the tibia and fibula, 

 it approaches the inner side of the leg as it descends, and lies behind the 

 tibia ; at its lower end it is placed midway between the inner malleolus 

 and the prominence of the heel. Very deeply seated at the upper part, 

 where it is covered by the fleshy portion of the gastrocnemius and soleus 

 muscles, it becomes comparatively superficial towards the lower part, being 

 there covered only by the integument and two layers of fascia, and by the 

 annular ligament behind the inner malleolus. It lies successively upon the 

 tibialis posticus, the flexor loiigus digitorum, and, at its lower end, directly 

 on the tibia and the ankle-joint. Behind the ankle, the tendons of the tibialis 

 posticus and flexor longus digitorum lie between the artery and the internal 

 malleolus ; whilst the tendon of the flexor longua pollicis is to the outer 

 side of the artery. 



Relation to the Veins and Nerve. The posterior tibial artery, like the 

 other arteries below the knee, is accompanied by two vense comites. The 

 posterior tibial nerve is at first on the inner side of the artery, but in the 

 greater part of its course the nerve is close to the outer side of the vessel. 



BRANCHES. The posterior tibial artery furnishes numerous small branches, 

 and one large branch the peroneal artery. 



SMALL BRANCHES. (a) Several muscular branches arise from the posterior tibial 

 artery, and are distributed principally to the deep-seated muscles in its neighbour- 

 hood, besides one or two of considerable size to the inner part of the soleus muscle. 



(6) The nutrient artery of the tibia, which is the largest of its kind in the bodj r , 

 arises from the posterior tibial artery near the commencement, and, after giving small 

 branches to the muscles, enters the nutrient foramen in the bone, and ramifies on 

 the medullary membrane. This vessel not unfrequently arises from the anterior 

 tibial artery. 



(c) A communicating branch from the peroneal artery, passing transversely, joins 

 the posterior tibial about two inches above the ankle-joint. 



THE PERONEAL ARTERY lies deeply along the back part of the leg, close 

 to the fibula. Arising from the posterior tibial artery about an inch below 

 the lower border of the popliteus muscle, it inclines at first obliquely 

 towards the fibula, and then descends nearly perpendicularly along that bone 

 and behind the outer ankle, to reach the side of the os calcis. In the 

 upper part of its course, this artery is covered by the soleus muscle and the 

 deep fascia, and afterwards by the flexor longus pollicis, which is placed over 

 it as far as the outer malleolus ; below this point, the vessel is covered only 

 by the common integument and the fascia. The peroneal artery rests at 

 first against the upper part of the tibialis posticus muscle, and afterwards, in 

 the greater part of its course, it is surrounded by fibres of the flexor longus 

 pollicis, lying close inside the projecting posterior ridge of the fibula. De- 



