ANTERIOR TIBIAL ARTERY 629 



The plantar metatarsal arteries, immediately before they bifurcate, send to the dorsum of 

 the foot a perforating branch each to the corresponding dorsal metatarsal arteries. They 

 anastomose by many small twigs with the dorsal metatarsal arteries, which also run along the 

 sides of the metatarsal bones, but more toward the dorsal aspect. Immediately above each 

 phalangeal joint the plantar digital vessels communicate by cross branches, forming a rete for 

 the supply of the articular end of the phalanges and the contiguous joints. At the distal end 

 of the toes they also freely anastomose with each other, forming a rete beneath the pulp and 

 around the matrix of the nail. The metatarsal and digital arteries are each accompanied by 

 two small veins. 



THE MEDL\L PLANTAR ARTERY 



The medial plantar artery [a. plantaris medialis] (figs. 501, 502) — much the 

 smaller of the two divisions into which the posterior tibial divides, passes forward 

 along the medial side of the sole of the foot usually to the first interosseous space. 

 Here it ends by anastomosing either with the first plantar metatarsal artery 

 derived from the plantar arch, or with the branch given off by the first plantar 

 metatarsal to the medial side of the great toe. 



Relations. — The artery is at first under cover of the abductor hallucis, but afterward lies 

 in the interval between that muscle and the flexor digitorum brevis. It is covered by the skin 

 and superficial fascia, but not by the plantar aponeurosis, since it lies between the central and 

 medial portions of that structure. 



The branches of the medial plantar are: — (1) The deep and (2) the superficial 

 branches. 



(1) The deep branch [ramus profundus], which at once divides — or it may come off as 

 several branches — to supply the muscles, articulations,and integument of the medial side of the 

 sole. Some of these branches form an anastomosis aroundthe medial margin of the foot, with 

 branches of the dorsalis pedis. 



(2) The superficial branch [ramus superficiahs] breaks up into very small twigs which ac- 

 company the digital branches of the medial plantar nerves, and anastomose with the plantar 

 metatarsal arteries in the first, second, and third spaces. At times a twig from one of these 

 branches joins the lateral plantar artery to form a superficial plantar arch. 



THE ANTERIOR TIBIAL ARTERY 



The anterior tibial artery [a. tibialis anterior] fig. 5C3— the smaller of the 

 two branches into which the popliteal arterj^ divides at the lower border of the 

 popliteus muscle — at first courses forward between the two heads of origin of the 

 tibialis posterior, and, after passing between the tibia and fibula above the upper 

 part of the interosseous membrane, runs downward on the front and lateral aspect 

 of the leg, between the anterior muscles, as far as the front of the ankle-joint. 

 Below the joint it is known as the dorsalis pedis. The course of the vessel is 

 indicated by a line drawn from the front of the head of the fibula to a point mid- 

 way between the two malleoli. 



The artery is accompanied by two veins which communicate with each other 

 at frequent intervals across it. It is also accompanied in the lower three-fourths 

 of its course by the deep peroneal nerve. The nerve, which winds round the head 

 of the fibula, and pierces the extensor digitorum longus, first comes into contact 

 with the lateral side of the arterj^ about the upper third of the leg; in the middle 

 third it is a little in front of the artery, and in the lower third again lies to its 

 lateral side. In addition to the named branches the anterior tibial arter}'- supplies 

 muscular twigs to the extensors of the toes and the tibiahs anterior. 



Relations. — The artery at first lies in the triangle formed by the two heads of the tibiahs 

 posterior and the pophteus muscle; and, as it passes above the interosseous membrane, it has 

 the tibia on one side and the fibula on the other. It is separated from the deep peroneal (ante- 

 rior tibial) nerve at its commencement by the neck of the fibula and the extensor digitorum 

 longus. This arrangement is homologous witii that met with in the forearm in the case of the 

 posterior interosseous artery and deep radial (posterior interosseous) nerve. 



Posteriorly in its course down the leg it lies in its upper two-thirds upon the interosseous 

 membrane, to which it is closely bound by fibrous bands; and in its lower third upon the front 

 of the tibia and the ankle-joint. 



To its medial side along its upper two-thirds is the tibialis anterior muscle; but at the lower 

 third it is crossed by the tendon of the extensor hallucis longus and then for the rest of its 

 course has this tendon overlapping it or to its medial side. 



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

 muscle; in its middle third with the extensor hallucis longus; but, as this muscle crosses to 

 the medial side of the artery, the vessel usually for a very short part of its course comes again 



