Lumbrical muscles

The lumbricals are small intrinsic hand muscles that originate from the tendons of the flexor digitorum profundus and insert into the extensor tendons of the digits.  They are also intrinsic muscles of the foot that originate from the tendon of the flexor digitorum longus, also inserting onto extensor tendons of the digits. In both the hand and the foot they flex the MCP or MTP joints, and extend the IP joints. 

In the hand the two lateral muscles (I and II) are innervated by the median n.  The two medial muscles (III and IV) are innervated by the ulnar n.

In the foot the first lumbrical is innervated by the medial plantar nerve while the other three are innervated by the lateral plantar nerve.