Plantar Muscles of the Foot: Layer 2

00:01 Now let's turn our attention to the second layer of muscles on the sole of the foot.

00:07 There's two muscles here, the first one is quadratus plantea.

00:10 And the second one more distally are the lumbricals.

00:14 Let's look at quadratus plantea.

00:16 The origin of quadratus plantea is the calcaneal tuberosity and the medial surface of the calcaneus bone.

00:23 It then extends distally to insert into the lateral side of the tendon or flexor digitorum longus.

00:31 Remember, flexor digitorum longus is an extrinsic muscle, so it's entered by the medial surface onto the sole of the foot and this muscle inserts into that tendon.

00:41 It's an important muscle which will serve to when it contracts to straighten and align those tendons which go on to insert onto the toe via flexor digitorum longus.

00:51 So make sure the flexion of those tendons is most efficient and occurs in a linear fashion.

00:58 So quadratus plantae is important.

01:00 Here we can see it's assisting flexor digitorum longus tendon in flexing those toes two to five.

01:08 If we then look at the lumbricals, the second muscle within this second layer.

01:13 We can see the lumbricals have an origin which is coming away from tenderness structures.

01:18 So the second third and fourth lumbricals, these come from the adjacent surface of flexor digitorum longus tendons.

01:27 So we can see these originating from those tendons or flexor digitorum longus.

01:32 The first lumbrical is coming from the medial side of that flexor digitorum longus tendon.

01:38 So the tendon is going to a specific digit.

01:41 Here, we can see the lumbricals are coming from that same named tendon but passing from that tendons surface, they pass all the way distally to the medial aspect of digits 2-5.

01:53 So these lumbricals are important in coming up the tendons and inserting onto the digits.

02:00 These muscles are involved in flexion of the metatarsophalangeal joints and also of extension of the interphalangeal joints.

02:08 So they take the same function as the lumbricals in the hand.

02:12 They obviously flex the metatarsophalangeal joints, therefore, but extend the inter phalangeal joints.

02:18 And that's just because of the position of these muscles and its tendon as they run across those joints.

02:25 If we have a look at the innervation of the second layer, we can see this first lumbrical is supplied by the medial plantar nerve.

02:32 Whereas the lumbricals 2-4 and quadratus plantea are generated by the lateral plantar nerve.

02:39 So the two plants are nerves, they're sharing the innervation.