Lower Limb LO6
6. Describe the primary arterial supply of the lower limb.
The primary blood supply to the lower limb is via the femoral a., a continuation of the external iliac a. beyond the inguinal ligament. The femoral a. is proximally located in the femoral triangle.
The boundaries of the femoral triangle are:
- Inguinal ligament (superior)
- Sartorius m. (lateral)
- Adductor longus m. (medial)
- Iliopsoas m. & Pectineus m. (posterior/deep)
Femoral neurovasculature lie in this triangular space as they enter the lower limb. The relationship of the neurovascular structures is important when accessing the vasculature – medial to lateral: femoral Vein, femoral Artery, femoral Nerve (VAN). Understanding this organization is of importance when trying to locate the femoral vein for cannulation. It is easily located by palpating the pulsations of the femoral artery (femoral pulse) and moving medially.
The femoral a. supplies the entire lower limb.
As the artery nears the distal end of the femoral triangle, it gives off the deep artery of thigh, which dives deep into the thigh muscles and runs medial to the femur to supply the deep muscles. It sends branches that perforate through the deep adductor muscles to supply the posterior compartment of the thigh. The deep artery of thigh terminates in the thigh.
The femoral a., on the other hand, continues through the anterior and medial thigh. As it nears the knee, it passes through a hiatus in an adductor muscle to relocate on the posterior surface of the distal femur. At this point it is behind the knee in the popliteal fossa and its name changes to popliteal a. The popliteal a. gives off numerous branches that supply the knee joint and form a complex anastomosis around this area.
The popliteal a. continues through the popliteal fossa to enter the leg. As it does, it splits into the anterior tibial a. and the posterior tibial a.
The anterior tibial artery passes through a space between the tibia and fibula just above the superior edge of the interosseous membrane to course down the leg on the anterior surface of the interosseous membrane. It supplies the anterior leg muscles. It passes across the dorsal ankle to run onto the dorsum of the foot as the dorsalis pedis a.
At the proximal leg, the posterior tibial a. gives off a lateral branch, the fibular (peroneal) a., which is a minor supply to the lateral compartment leg muscles (anterior tibial a. is the major supply). The posterior tibial artery continues down the posterior leg to supply the superficial and deep groups of posterior leg muscles. It courses around and behind the medial malleolus with the tendons of the deep posterior leg muscles to enter the plantar region of the foot. Here it splits into medial & lateral plantar aa. that connect to form the plantar arch at the metatarsal portion of the foot.