» Vascularization of the Hindlimb

The chief artery of the limb, the femoral artery, directly continues the external iliac artery (Fig. 24.17/1 and 3). It reaches the femoral triangle, traveling in company with the femoral vein and nerve and almost at once detaches the saphenous artery and several larger muscular branches.

The muscular branches include deep and caudal femoral arteries (Fig. 24.17/4 and 9) that anastomose with each other and with other more proximal and more distal arteries, forming an alternative pathway available when the chief trunk is obstructed. The femoral artery then passes obliquely over the femur to gain the caudal aspect of the stifle, where it passes between the heads of the gastrocnemius. The segment at the stifle, known as the popliteal artery, divides into cranial and caudal tibial arteries in the upper part of the leg.

The larger cranial tibial artery (Fig. 24.17/11) passes through the interosseous space between the fibula and tibia to gain the dorsolateral aspect where it turns distally between the muscles and the bone. It comes to the surface at the hock and continues as the dorsal pedal artery and then, on entering the groove between the cannon and lateral splint bones, as the dorsal metatarsal artery. A perforating branch (Fig. 24.17/13) of the dorsal pedal artery passes between the tarsal bones to reach the plantar aspect of the limb, where it anastomoses with branches of the saphenous artery. The dorsal metatarsal artery, the major supply to the foot, is well placed at the proximal end of the cannon for evaluation of the pulse. Toward the fetlock, it passes under the free end of the splint bone to gain the plantar aspect of the cannon, where it is reinforced by small branches from the saphenous.

The caudal tibial artery first runs distally in the deep flexor (Fig. 24.17/12). Toward the hock it enters the space before the calcanean tendon and sends a short S-shaped anastomosis to the nearby saphenous artery and a longer branch that reascends the leg to join the caudal femoral artery. The saphenous artery, thus reinforced, divides into medial and lateral plantar arteries that descend toward the fetlock (Fig. 24.17/15). These and the deeper plantar metatarsal arteries are individually of no great importance and may eventually fade away or join the dorsal metatarsal artery or its digital divisions.

The deep veins are largely satellite to the arteries. As in the forelimb, certain superficial trunks, including the medial and lateral saphenous veins, run alone. A branch of the former is often prominent where it crosses the dorsal aspect of the hock, and its swelling ("blood spavin") may occasionally be mistaken for a distention of the dorsal joint pouch (Fig. 24.11/4 and 8). Within the leg, the saphenous veins run between the calcanean tendon and the caudal muscle mass, one to each side (Fig. 24.8/10 and 12). The medial vein later crosses the medial aspect of the thigh to open into the femoral vein. The lateral vein joins the caudal femoral vein at the stifle.

Lymph draining from the distal part of the limb passes mainly to the group of popliteal nodes tucked within the popliteal fossa between the biceps and semitendinosus. Efferent vessels from this group and additional vessels that arise within the thigh proceed mainly to the deep inguinal nodes within the femoral triangle. Some lymph from superficial structures passes to the subiliac nodes, which drain into the lateral and medial iliac nodes. The courses of certain lymphatic vessels may be manifested as cords visible through the skin in some lymph-borne infections.