Relations. Anterior.-It is in contact anteriorly, and proximo-distally, with the tibialis posterior, the flexor digitorum longus, the posterior surface of the tibia, and the posterior ligament of the ankle-joint. Posterior. The artery is crossed about 37 mm. (an inch and a half) distal to its origin by the tibial nerve. Elsewhere it is in contact with the intermuscular fascia which binds down the deep layer of muscles. More superficially the proximal half of the artery is covered by the fleshy parts of the soleus and gastrocnemius muscles, between which is the plantaris; the distal half of the artery is much nearer the surface, and is covered only by skin and fasciæ, except at its termination, where it lies deep to the laciniate ligament. Lateral and Medial.—The artery is accompanied by two venæ comites, one on each side. The tibial nerve lies at first on the medial side of the vessel, then crosses posterior to it, and is continued distally on its lateral side. In the most distal part of its course the artery is separated from the medial malleolus by the tendons of the tibialis posterior and the flexor digitorum longus, whilst the tendon of the flexor hallucis longus lies postero-lateral to it. Branches.--The posterior tibial gives off numerous branches, the largest of which, the peroneal, forms one of the chief arteries of the leg. The branches include (1) Large muscular branches which are distributed to the soleus, the tibialis posterior, the flexor digitorum longus, and the flexor hallucis longus. They anastomose with the deep sural branches of the popliteal artery and the lower medial genicular artery. (2) A fibular branch passes laterally, to the neck of the fibula, where it anastomoses with the inferior lateral genicular and the deep sural arteries, and supplies the adjacent muscles. It (3) The peroneal artery (Fig. 781) is the largest branch of the posterior tibial. arises about 25 mm. (an inch) below the distal border of the popliteus, curves laterally across the proximal part of the tibialis posterior to the medial crest of the fibula, along which it passes to the distal part of the interosseous space. About 25 mm. (an inch) proximal to the ankle-joint it gives off a perforating branch and then passes, posterior to the tibio-fibular syndesmosis and lateral malleolus, to the lateral side of the heel and the foot. It supplies the ankle, the tibio-fibular syndesmosis, and the talo-calcanean joint, and anastomoses with the medial calcanean branch of the lateral plantar artery, and with the tarsal and arcuate branches of the dorsalis pedis. As the peroneal artery passes laterally from its origin it lies posterior to the tibialis posterior, and is covered posteriorly by the deep intermuscular fascia and by the soleus. As it descends along the medial crest of the fibula it lies in a fibrous canal between the tibialis posterior in front and the flexor hallucis longus behind. The peroneal artery is accompanied by two venæ comites, and is crossed anteriorly and posteriorly by communicating branches between them. Branches. (a) Muscular branches are distributed to the soleus, tibialis posterior, flexor hallucis longus, and the peroneal muscles. Some pass through the interosseous membrane and supply the anterior muscles of the leg. (b) A nutrient branch enters the nutrient foramen of the fibula. (c) A communicating branch passes across the back of the distal end of the shaft of the tibia, about 25 mm. (an inch) above the tibio-fibular syndesmosis, to anastomose with the posterior tibial artery. (d) The perforating branch passes forwards at the junction of the distal border of the interOsseous membrane and the interosseous tibio-fibular ligament, and runs, in front of the ankle, to the dorsum of the foot, where it anastomoses with the lateral malleolar branch of the anterior tibial artery and with the tarsal branch of the dorsalis pedis; it also supplies branches to the tibio-fibular syndesmosis, to the ankle-joint, and to the peronæus tertius. (4) The nutrient branch, the largest of the nutrient group of arteries to long bones, springs from the proximal part of the posterior tibial, pierces the tibialis posterior, and enters the nutrient foramen on the posterior surface of the tibia. In the interior of the bone it divides into proximal and distal branches, the former passing towards the proximal extremity of the bone, and the latter towards the distal extremity. Before entering the tibia the nutrient artery gives small muscular branches. (5) A communicating branch unites the posterior tibial to the peroneal artery about 25 mm. (an inch) above the tibio-fibular syndesmosis. It passes posterior to the shaft of the tibia and anterior to the flexor hallucis longus. (6) Cutaneous branches are distributed to the skin of the medial and posterior part of the leg. (7) A posterior medial malleolar branch is distributed to the medial surface of the medial malleolus, anastomosing with a corresponding branch of the anterior tibial artery. PLANTAR ARTERIES. (8) The medial and lateral plantar arteries are the terminal branches of the posterior tibial artery. They arise, under cover of the origin of the ligamentum laciniatum, midway between the tip of the medial malleolus and the most prominent part of the medial side of the os calcis (Figs. 781, 782). Arteria Plantaris Medialis.-The medial plantar artery is the smaller of the two terminal branches of the posterior tibial artery. It passes forwards, along the medial side of the foot, in the interval between the abductor hallucis and the flexor digitorum brevis, to the head of the first metatarsal bone, where it terminates by uniting with the plantar digital branch of the dorsalis pedis, which is distributed to the medial side of the great toe. In its course forwards it Quadratus planta gives off a superficial branch, which ramifies on the superficial surface of the abductor hallucis; branches to the adjacent muscles and articulations, and to the subjacent skin; it also gives three digital branches which anasto mose, at the roots of the three medial interdigital Transverse head clefts, with the medial plantar metatarsal arteries. Some of the cutaneous branches of the medial plantar artery anastomose, round the medial border of the foot, with the medial cutaneous branches of the dorsalis pedis artery. Arteria Plantaris Lateralis.-The lateral plantar artery is the larger of the two terminal branches of the posterior tibial artery. It runs forwards and laterally, first between the flexor digitorum brevis superficially and the quadratus plantæ deeply, and then, in the interval between the flexor digitorum brevis and the abductor digiti quinti, to the medial side of the base of the fifth metatarsal bone, where it turns abruptly medially and, gaining a deeper plane, passes across the bases of the metatarsal bones and the origins of the interossei, and above the oblique head of the adductor of the great toe, to the lateral side of the base of the first metatarsal bone, where it terminates by anastomosing with the dorsalis pedis artery. The last part of the artery is convex forwards and forms the plantar arch, which is completed by the profunda branch of the dorsalis pedis. Branches.- Between its origin and the base of the fifth metatarsal the lateral - plantar artery gives off (a) the medial calcanean branch, which is distributed to the skin and the subcutaneous tissue of the heel. (6) Muscular branches to the abductor hallucis, flexor digitorum brevis, quadratus plantæ, and abductor digiti quinti. (c) Cutaneous branches to the skin of the lateral side of the foot. Between the base of the fifth metatarsal bone and the first interosseous space it forms the plantar arch, and gives off (d) four plantar metatarsal branches; (e) three posterior perforating arteries to the dorsal metatarsal arteries; and (ƒ) articular branches to the tarsal joints. The fifth or most lateral metatarsal branch runs along the lateral side of the little toe, supplying the skin, joints, and the flexor tendons with their synovial sheaths. The three medial plantar metatarsal branches, second, third, and fourth, run forwards on the plantar surfaces of the interossei, the medial two lying dorsal to the oblique head of the adductor of the great toe, and all three passing dorsal to the transverse head of the adductor. At the bases of the interdigital clefts the second, third, and fourth plantar metatarsal arteries divide into plantar digital arteries which run along the plantar aspects of adjacent toes, and supply skin, joints, and the flexor tendons and sheaths. Opposite the last phalanx of each toe the digital arteries of opposite sides of the toe anastomose together. The posterior perforating arteries are three in number; they pass dorsalwards through the three lateral intermetatarsal spaces, between the heads of the dorsal interosseous muscles, and terminate by uniting with the corresponding dorsal metatarsal arteries. Anterior perforating branches which communicate with the dorsal metatarsal arteries are given off from two or three of the plantar metatarsal arteries just before they divide. The articular branches are numerous and irregular; they supply the joints and ligaments of the tarsus on its plantar aspect. ARTERIA TIBIALIS ANTERIOR. The anterior tibial artery, the smaller of the two terminal divisions of the popliteal, commences opposite the distal border of the popliteus muscle, and terminates in front of the ankle, where it is continued into the dorsal artery of the foot. Course and Relations. From its origin, at the back of the leg, the artery passes anteriorly, between the two slips of the proximal part of the tibialis posterior and above the proximal border of the interosseous membrane. It then runs distally, resting, in the proximal two-thirds of its course, against the anterior surface of the interosseous membrane and, subsequently, on the distal part of the tibia and the anterior ligament of the ankle-joint. In the proximal third of the anterior compartment of the leg it lies between the extensor digitorum longus laterally and the tibialis anterior medially; in the middle third it is between the extensor hallucis longus and the tibialis anterior; in the distal third the extensor hallucis longus crosses in front of the artery and reaches its medial side, and the most distal part of the vessel lies between the tendon of the extensor hallucis longus on the medial side and the most medial tendon of the extensor digitorum longus on the lateral side. The deep peroneal nerve (O.T. anterior tibial) is at first well to the lateral side of the artery, but it soon passes in front of the vessel, and it lies in front of the middle third of the artery; more distally the nerve is usually found on the lateral side again, and at the ankle it intervenes between the artery and the most medial tendon of the extensor digitorum longus. Two venæ comites, with numerous intercommunications, accompany the artery. Obviously the anterior tibial artery is, at least in its proximal part, deeply placed; moreover, its lateral muscular boundaries overlap it. In the distal two-thirds of its extent it is, however, easily accessible from the surface; and beyond being covered by the nerve and crossed by the tendon, as already described, is only covered, in addition, by skin, fascia, and the transverse crural ligament. Branches. Close to its origin the artery gives off fibular and posterior tibial recurrent branches; after it reaches the front of the leg it gives off anterior tibial recurrent, muscular, cutaneous, medial malleolar, and lateral malleolar branches. and passes upwards and medially, between the superficial and deep layers of the superficial fascia of the abdominal wall, towards the umbilicus. It supplies the sub-inguinal glands and the integument, and anastomoses with its fellow of the opposite side, with the inferior epigastric, and with the superficial circumflex iliac and superficial external pudendal arteries. (c) Arteria Pudenda Externa Superficialis.-The superficial external pudendal artery also springs from the front of the femoral artery, and, after piercing the femoral sheath and the fascia cribrosa, runs upwards and medially towards the pubic tubercle, where it crosses superficial to the spermatic cord and divides into terminal anterior scrotal or labial branches according to the sex. It supplies the integument of the lower part of the abdominal wall, the root of the dorsum of the penis in the male, and the region of the mons Veneris in the female, and it anastomoses with its fellow of the opposite side, with the deep external pudendal, with the dorsal artery of the penis, and with the superficial epigastric artery. (2) Rami Musculares. The muscular branches are distributed to the pectineus and the adductor muscles on the medial side, and to the sartorius and the vastus medialis on the lateral side. (3) Arteria Pudenda Externa Profunda.-The deep external pudendal artery arises from the medial side of the femoral. It runs medially, anterior to the pectineus, and either anterior or posterior to the adductor longus, to the medial side of the thigh; it then pierces the deep fascia, and terminates in the scrotum, where it anastomoses with the posterior scrotal branches of the perineal and the anterior scrotal branches of the superficial external pudendal arteries, and with the external spermatic branch of the inferior epigastric artery. In the female it terminates in the labium majus. (4) Arteria Profunda Femoris.-The profunda artery (Fig. 778) is the largest branch of the femoral artery. It arises about 37 mm. (an inch and a half) distal to the inguinal ligament, from the lateral side of the femoral artery. It curves backwards and medially, passes posterior to the femoral artery, and runs distally, close to the medial aspect of the femur, to the distal third of the thigh, where it perforates the adductor magnus and passes to the back of the thigh. Its termination is known as the fourth perforating artery. As the profunda descends it lies anterior to the iliacus, the pectineus, the adductor brevis, and the adductor magnus. It is separated from the femoral artery by its own vein, by the femoral vein, and by the adductor longus muscle. Branches. (a) Muscular branches are given off from the profunda, both in the femoral trigone and whilst it lies between the adductor muscles; many of them terminate in the adductors, others pass through the adductor magnus, and terminate in the hamstrings, where they anastomose with the transverse branch of the medial circumflex and with the proximal muscular branches of the popliteal artery. (b) The lateral circumflex artery (Figs. 778 and 779) springs from the lateral side of the profunda, or occasionally from the femoral artery proximal to the origin of the profunda. It runs laterally, anterior to the iliacus and between the superficial and deep branches of the femoral nerve, to the lateral border of the femoral trigone; then, passing posterior to the sartorius and the rectus femoris, it terminates by dividing into three terminal branches -the ascending, the transverse, and the descending. Before its termination it supplies branches to the muscles mentioned and to the proximal part of the vastus intermedius. (i.) The ascending terminal branch runs proximally and laterally, posterior to the rectus femoris and the tensor fascia latæ, along the linea intertrochanterica, to the anterior borders of the glutæi, medius and minimus, between which it passes to anastomose with the deep branches of the superior gluteal artery. It supplies twigs to the neighbouring muscles, anastomoses with the gluteal, the deep circumflex iliac, and the transverse branch of the lateral circumflex arteries, and, as it ascends along the linea intertrochanterica, it gives off a branch which passes, between the two limbs of the ilio-femoral ligament, into the hip-joint. (i.) The transverse terminal branch is small; it runs laterally, between the vastus intermedius and the rectus femoris, passes into the substance of the vastus lateralis, winds round the femur, and anastomoses with the ascending and descending branches, with the perforating branches of the profunda, and with the inferior gluteal and medial circumflex arteries. (iii.) The descending terminal branch runs distally, posterior to the rectus and along the anterior border of the vastus lateralis, accompanied by the nerve to the latter muscle. It anastomoses with the transverse branch, with twigs of the inferior perforating arteries, with the arteria genu suprema of the femoral, and with the superior lateral genicular branch of the popliteal artery. (c) The medial circumflex artery springs from the medial and posterior part of the profunda, at the same level as the lateral circumflex, and runs backwards, through the floor of the femoral trigone, passing between the psoas major and the pectineus; then it crosses the upper border of the adductor brevis, and continuing backwards, below the neck of the femur, it passes between the adjacent borders of the obturator externus and the adductor brevis to the upper border of the adductor magnus, where it divides into two terminal branches, a transverse and a profunda branch (O.T. ascending). Branches.(i.) An acetabular branch is given off as the artery passes below the neck of the femur. It ascends to the acetabular notch where it anastomoses with twigs from the posterior branch of the obturator artery, and it sends branches into the acetabular fossa and along the ligamentum teres to the head of the femur. (ii.) A superficial branch, which passes medially, anterior to the pectineus and between the adductors brevis and longus. (iii.) Muscular branches are given off to the neighbouring muscles. The largest of these branches usually arises immediately before the termination of the artery; it runs distally, on the anterior aspect of the adductor magnus, and anastomoses with the muscular branches of the profunda artery. (iv.) The profunda terminal branch (ascending) passes upwards and laterally, between the obturator externus and the quadratus femoris to the trochanteric fossa of the femur, where it anastomoses with branches of the superior and inferior gluteal arteries. (v.) The transverse terminal branch runs backwards to the hamstring muscles, usually between the lower border of the quadratus femoris and the upper border of the adductor magnus, but it may pierce the upper part of the |