5. A. tibialis anterior.—The anterior tibial artery is the continuation of the popliteal after its passage through the interosseous membrane between tibia and fibula to the dorsal side of the lower leg. Here it passes distad, lying against the interosseous membrane, between the extensor longus digitorum and the tibialis anterior muscle, or partly imbedded in the substance of the latter. It passes, lying beneath the tendons of these muscles, through the transverse ligament proximad of the malleoli, thus reaching the dorsum of the foot. It extends distad across the tarsus to the space between the second and third metatarsals, and through this space to the plantar side of the foot ([Fig. 128]). Here it receives one or two small branches (a and d) from the plantar branch of A. saphena (forming with them the plantar arch (c)), and passing distad and slightly laterad, divides into three main portions (e). These (Aa. digitales plantares) pass to the three intervals between the digits. The medial one passes along the lateral side of the second digit; the next divides, sending a branch to the lateral side of the third digit and the medial side of the fourth; the lateral one passes along the medial border of the fifth digit. The Aa. digitales plantares send numerous branches to the interosseous muscles.

[Fig. 128].—Deep Arteries on the Plantar Surface of the Foot.

a, medial twig from plantar branch of A. saphena; b, A. tibialis anterior (or plantaris profunda); c, plantar arch; d, lateral twig from plantar branch of A. saphena; e, terminal branches from A. tibialis anterior.

Branches of the tibialis anterior:

a. A. tibialis recurrens.—Immediately after passing through the interosseous membrane the anterior tibial sends a small artery proximad to the knee-joint.

b. Rami musculares.—Numerous short branches throughout the course of the artery, to the muscles about it.

c. Ramus superficialis.—A larger branch leaves the lateral surface of the artery about one-third the distance from the knee to the ankle and passes along with the superficial peroneal nerve, at first beneath M. peroneus longus, then superficially. It passes onto the dorsal surface of the foot and becomes connected with terminal branches of A. saphena.

d. A. tarsea medialis.—This arises from the tibialis anterior just distad of the transverse ligament through which it passes at the ankle, passes over the medial surface of the astragalus, and is distributed to the ligaments about the ankle-joint. It anastomoses with the plantar branch of A. saphena.

e. A. metatarsea.—The metatarsal artery passes laterad from the tibialis anterior at the distal boundary of the tarsus, on the dorsal surface of the foot. It sends branches distad in the intervals between the third and fourth and the fourth and fifth metatarsals.