<P> In the second layer, the quadratus plantae, located below flexor digitorum brevis, inserts into the tendon of flexor digitorum longus on which the lumbricals originate . </P> <P> In the third layer, the oblique head of adductor hallucis joins the muscle's transversal head on the lateral side of the big toe . Medially to adductor hallucis are the two heads of flexor hallucis brevis, deep to the tendon of flexor hallucis longus . The considerably smaller flexor digiti minimi brevis on the lateral side can be mistaken for one of the interossei . </P> <P> In the fourth layer . the dorsal and plantar interossei are located between and below the metatarsal bones and act as antagonists . </P> <P> The central compartment is shared by the lumbricals, quadratus plantae, flexor digitorum brevis, and adductor hallucis; the medial compartment by abductor hallucis, flexor hallucis brevis, abductor digiti minimi, flexor digiti minimi brevis, and opponens digiti minimi (often considered part of the former muscle); whilst the lateral compartment is occupied by extensor digitorum brevis and extensor hallucis brevis . </P>

Where is the dorsum of the foot located