Now that we’ve seen the muscles for the big toe and the fifth toe, we need to see how all these short muscles fit together. To do that, we’ll put the long flexor tendons, and then the central group of muscles back into the picture.
First we’ll add flexor hallucis longus to the picture. Flexor hallucis longus lies deep to abductor hallucis as it enters the foot. Here’s flexor digitorum longus, entering the foot along with flexor hallucis longus. The tendons of flexor digitorum longus cover up adductor hallucis. Here are the lumbricals, flexor accessorius, and last of all flexor digitorum brevis.
Now that we’ve seen all the muscles of the foot, let’s get a complete picture of the layer of deep fascia that encloses them all, the plantar fascia.
The central, thickened part of the plantar fascia is the plantar aponeurosis, which we’ve seen already. The medial and lateral parts of the plantar fascia extend on each side of the plantar aponeurosis. On the medial side the plantar fascia covers abductor hallucis.
On the lateral side it covers abductor digiti minimi. Here on the lateral side there’s a marked thickening of the plantar fascia, called the lateral cord of the plantar aponeurosis, which goes from here on the calcaneus, to here on the base of the fifth metatarsal. The lateral cord of the plantar aponeurosis helps to support the longitudinal arch of the foot, on the lateral side.