Leg - Cross Section

Three compartments of the leg:

Membranes

Anterior septum

Extends anterolaterally from the fibula and separates the anterior and lateral compartments.

Posterior septum

Extends posterolaterally from the fibula and separates the lateral and posterior compartments.

Interosseous membrane

Muscles of the anterior compartment (from medial to lateral):

Tibialis anterior

Extensor hallucis longus

Extensor digitorum longus

Muscles of the lateral compartment (from deep to superficial):

Fibularis brevis

Fibularis longus

Muscles of posterior compartment:

Deep:

Flexor digitorum longus

Tibialis posterior

Flexor hallucis longus

Superficial:

Soleus

Gastrocnemius (medial and lateral bellies join at calcaneal tendon)

End of essential/beginning of advanced

Neurovascular structures:

Anterior compartment:

Lateral compartment:

Deep posterior compartment:

Fibular artery and vein (which are near the fibula).
Posterior tibial artery and vein.
Tibial nerve, which forms when the sciatic nerve unbundles in the posterior thigh.

Cutaneous nerves and superficial veins:

Great saphenous vein
Saphenous nerve (which is the terminal branch of the femoral nerve).
Small saphenous vein, which meets the great saphenous vein in the posterior leg.
Sural nerve, which comprises branches of the tibial and common fibular nerves (though individual variation is common).
Lateral sural cutaneous nerve, which is a branch of the common fibular nerve.
Sural communicating branch of the lateral sural cutaneous nerve lies between the lateral cutaneous and medial sural nerves.

Key points:

Anterior compartment muscles are innervated by the deep fibular nerve, and they primarily provide foot dorsiflexion and toe extension (in addition to eversion and inversion of the foot).
Lateral compartment muscles are innervated by the superficial fibular nerve, and that they provide foot plantar flexion and eversion.
Posterior compartment muscles are innervated by the tibial nerve, and that they provide foot and toe plantar flexion (in addition to acting at the knee and, in the case of tibialis posterior, inverting the foot).