Cutaneous Innervation – Lower Limb: Superficial Structures and Cutaneous Innervation

00:01 If we move on to the cutaneous innervation, then this is very similar to the upper limb, and we have a whole series of dermatomes, regions of the skin on the lower limb that have specific cutaneous innervation. We can see we have T12, L1, L2, L3, L4, L5, and then we move on to the sacral spinal cord segments, as then we pass up the posterior surface of the limb. So if we look at this in more detail, the cutaneous nerve supplies the skin of the lower limb creating these dermatomes, and each dermatome is innervated by a spinal cord segment. So we can see L1 through to S5, the perianal region. We can even see details here, L4, L5, and S1 supplying the palm of the foot.

00:50 If we look at L1 to L5, you can see these were series of bands running down the anterior aspect of the lower limb. So, around the knee region and the medial leg, we have L4.

01:02 And the medial leg to the great toe, we have L5, we can see running down here. S1 to S5 forms more vertical bands that are running up the posterior aspect of the lower limb, and S1, we have the lateral foot we can see here, and we also have the heel. So we can see we have the dermatomal distribution running over the anterior and posterior surfaces of the lower limb. Again, we have the dermatomal distribution, but we also have specific cutaneous nerves that are coming from the lumbosacral plexus which we'll detail. Here, we can see specific nerves supplying specific regions. We can pick up the lateral cutaneous nerve of the thigh that supply the lateral aspect of the thigh. We can see the genitofemoral nerves coming here supplying a small region on the anterior thigh. Cutaneous branches from the femoral nerve. We've got the saphenous nerve, a branch of the femoral nerve supplying the medial aspect of the leg. We can see the common fibular supplying the lateral aspect of the leg. And posteriorly, we can see the posterior cutaneous nerve of the thigh supplying the posterior aspect of the thigh. We can see obturator nerve supplying the medial aspect.

02:26 And we can see clunial nerves supplying the skin over the gluteal region. Again, we have those named branches: iliohypogastric, ilioinguinal, we can see these supplying parts of the abdominal wall and the lower abdomen passing over the inguinal region, lateral cutaneous nerve of the thigh, and the genitofemoral and the obturator I've already mentioned. We can go on to detail the femoral, saphenous, common fibular, deep fibular and superficial fibular nerves.

02:58 And we can see how these are supplying various regions of the lower limb. So in this lecture, we've looked at the fascia of the lower limb, both the superficial and deep, specifically looking at the fascia lata. We looked at the venous drainage, the dorsal venous network giving rise to the great saphenous vein and the short saphenous vein with these draining into the femoral vein and the popliteal vein, respectively. We then looked at the cutaneous innervations with the dermatomal distribution. Again, this is determined by the developmental process similar to the upper limb. So I didn't mention it in any detail today but it's the same process. And the cutaneous nerves from the spinal cord segments, L1 through S5 that supplies the skin of the lower limb.