Okay so this is the second tutorial on the muscles of the leg, so in this tutorial i’m going to cover the muscles of the anterior and lateral compartments. So these compartments are supplied by the common peroneal branch of the sciatic nerve. So the sciatic nerve splits into two branches at the popliteal fossa. The tibial branch supplies the posterior compartment, and then you’ve got the common fibular, or common peroneal branch, which winds round laterally, over the head of the.the lateral head of the gastrocnemius, over the.
Neck of the fibula, where it’s vulnerable to impact injuries and fractures, and then it splits into two branches which supply the anterior and the lateral compartments. So I’ll just fade away the muscles and then you can see how this nerve splits. So you’ve got the common fibular branch coming around laterally, and then it splits into these two branches: you’ve got the superficial branch, which supplies the muscles of the lateral compartment, and you’ve got the deep branch, which supplies the anterior compartment. So the muscles of.
The anterior compartment mainly act to dorsiflex, extend to the toes, and to invert the foot, and there are four muscles in this compartment, and this compartment is supplied by the deep branch of the common fibular nerve. The lateral compartment only has two muscles, and these muscles mainly act to evert the foot. And this compartment is supplied by the superficial branch of the common fibular nerve. Okay so you have two muscles in the lateral compartment of the leg, you’ve got the peroneus longus, or the fibularis longus, which is this muscle.
Here. and you’ve got the fibularis brevis, which lies deep to the fibularis longus, and it attaches a bit lower down on the fibula. So I’ll just show you the fibularis longus muscle. So the fibularis longus muscle, as you can see its origin, attaches on the upper lateral surface of the fibula, and also on the lateral side of the head of the fibula, and it has an interesting tendon, because it actually crosses over underneath the foot to insert medially at the distal end of the medial cuneiform bone, and at the base of.
The proximal, sorry, the base of the first metatarsal here. so if we just follow this tendon round, you can see it runs down behind the lateral malleolus and then it descends and curves forwards on the lateral side of the calcaneus and then passes under the foot. And it then passes under the cuboid bone, and in this bone there’s a groove for the.for the tendon. So I’ll just show you that. So if we just look, I’ve just rotated the model and we’re looking at the underside of the foot the plantar surface of the foot, so.
This is the cuboid bone, which is one of the tarsal bones that sits laterally. so the tendon of the peroneus longus actually runs in a groove in this cuboid bone. I think it’s a little bit out of place here, but you can see this groove here, so the tendon runs underneath the foot, through the groove on the cuboid bone and attaches to the base.base of the first metatarsal and also distally on the medial cuneiform bone. So you can just see that tendon coming across, and it inserts distally on the medial cuneiform, and at the.
Base of this first metatarsal. so what this muscle does is that it actually everts the foot and it can also assist in plantarflexion. So you can just imagine, so seeing the insertion point here, you could just visualise if this muscle were to contract it would pull this, pull the foot round into eversion. So eversion is when the soles of the feet face away from each other, and inversion is when you bring the soles of the feet to face each other. So another point about the peroneus longus is that it actually provides support for the.
Arches of the foot. so it mainly supports the lateral and transverse arches, and if you remember in my last tutorial, the tibialis posterior also provided support to the arch, due to its insertion on the medial aspect of the foot, and there’s another muscle which I’ll come on to talk about later in this tutorial, called the tibialis anterior, which also inserts medially on the foot, and contributes to arch support. So I’ve just brought back in all the muscles, and this muscle here is the tibialis anterior, which I’ll talk about later, and.