626 THE BLOOD-VASCULAR SYSTEM 



The branches of the posterior tibial artery are: — (1) The fibular; (2) the 

 peroneal; (3) the tibial nutrient; (4) the communicating; (5) the posterior medial 

 malleolar; (6) the medial calcanean, and (7) the terminal, medial and lateral 

 plantar. 



(1) The fibular or superior fibular branch [ramus fibularis], which frequently arises from the 

 beginning of the anterior tibial, runs upward and laterally toward the head of the fibula. It is 

 small and gives twigs to the soleus, peroneus longus, and extensor digitorum longus, and anasto- 

 moses with the inferior lateral articular and the lateral sural arteries. 



(2) The peroneal artery [a. peronea] is a large vessel which (figs. 498, 500), 

 arises from the posterior tibial about 2.5 cm. (1 in.) below the lower border of the 

 popliteus muscle. At first forming a gentle curve convex laterally, it approaches 

 the fibula, and continues its course downward close to that bone as far as the lower 

 end of the interosseous membrane, where it gives off a large branch, the perforating 

 (anterior peroneal), and then, passing over the back of the inferior tibio-fibular 

 joint, terminates by breaking up into a network, which is distributed over the 

 back of the lateral malleolus and lateral surface of the calcaneus (figs. 500, 504). 

 It is accompanied by two venae comitantes. Besides the named branches it 

 supplies twigs to the flexor hallucis longus, tibialis posterior, tibialis anterior, 

 peronei and soleus; also to the integument on the lateral side of the leg. 



Relations. — At its upper part it is deeply placed between the tibialis posterior and soleus 

 muscles, and beneath the deep or intermuscular fascia. For the rest of its course to the ankle 

 it lies beneath, or sometimes in the substance of, the flexor hallucis longus in the angle between 

 the fibula and interosseous membrane. After giving off the perforating branch, it is only cov- 

 ered, as it lies behind the tibio-fibular articulation, by the integuments and deep fascia, and in 

 this part of its course is sometimes called the posterior peroneal. 



The branches of the peroneal artery are: — (a) The perforating (anterior 

 peroneal) ; (b) the fibular nutrient; (c) the communicating; (d) the lateral malleolar; 

 (e) the lateral calcanean; and (/) the terminal. 



(a) The perforating (or anterior peroneal) branch [ramus perforans] arises from the front 

 of the peroneal artery at the lower part of the interosseous space, and, passing through the 

 interosseous membrane, runs downward over the front of the inferior tibio-fibular joint, beneath 

 the peroneus tertius, and supplies this muscle and the inferior tibio-fibular joint. It anasto- 

 moses with the tarsal, arcuate (metatarsal) and lateral malleolar branches of the anterior tibial 

 artery, and with the lateral plantar artery on the lateral side of the foot, forming a plexus over 

 the ankle (fig. 503). 



(6) The fibular nutrient [a. nutritia fibulae] enters the nutrient foramen of the fibula. 



(c) The communicating branch [ramus communicans] passes medially in front of the tendo 

 Achillis to anastomose with the communicating branch of the posterior tibial. The usual 

 situation of this communication is from 2.5 to 5 cm. (1 to 2 in.) above the ankle-joint. 



(d) The lateral posterior malleolar artery [a. malleolaris poster, laterahs] anastomoses on 

 the lateral malleolus with the anterior lateral malleolar of the anterior tibial artery to form the 

 lateral malleolar rete. 



(e) The lateral calcaneal branches [rami calcanei laterales] come off from the peroneal below 

 the point at which the perforating is given off, and are distributed over the lateral surface of the 

 calcaneus. 



(/) The terminal branch or posterior peroneal, the continuation of the peroneal artery, 

 anastomoses with the other arteries distributed to the lateral malleolus and heel. 



(3) The tibial nutrient artery [a. nutritia tibia^], a vessel of large size, leaves the posterior 

 tibial at its upper part, pierces the tibialis posterior, and enters the nutrient foramen in the 

 upper third of the posterior surface of the tibia. In the interior of the bone it divides into two 

 branches: an ascending or smaller, which runs upward toward the head of the bone; and a de- 

 scending or larger, which courses downward toward the lower end. It gives off two or three 

 muscular twigs to the tibialis posterior before it enters the foramen. The nutrient artery of the 

 tibia is the largest nutrient artery of bone in the body, and is accompanied by a nerve given off 

 by the nerve to the popliteus. 



(4) The communicating brancli [ramus communicans] arises from the posterior tibial about 

 5 cm. (2 in.) above the medial malleolus, and, pas.sing transversely across the tibia beneath 

 the flexor hallucis longus and tendo Achillis, anastomoses with the communicating branch of 

 the peroneal. 



Frequently an inferior communicating branch between the posterior tibial and peroneal 

 arteries is likewise present in the loose connective tissue beneath or behind the tendo Achillis. 



(5) The posterior medial malleolar branch [ramus malleolaris posterior mediahs] divides 

 for distribution over the medial malleolus, anastomosing with the other arteries entering into 

 the medial malleolar rele [rete malleolare mcdiale] which is formed over the portion of bone. 

 In its cour.se to the malleolus it runs beneath the flexor digitorum longus and tibiahs posterior 

 muscles. 



(6) The medial calcanean branches [rami calcanei mediales] are distributed to the soft 

 parts over the medial sidc' of flic calcaneus. The.sc branches come off from the posterior tibial 

 just before its bifurcation, and anastomose with tlic medial malleolar and peroneal arteries. 



(7) The terminal branches are the lateral and medial plantar arteries. 



