The gastrocnemius is a strong muscle lying on the superficial and posterior aspect of leg. It consists of two heads, a medial and a lateral head. The medial head is stronger, arising from the popliteal surface of the femur. The lateral portion, on the other hand, originates from a point located right above the lateral condyle of the same bone. At their origins, both heads constitute the inferior border of the popliteal fossa.
The gastrocnemius muscle runs down along the posterior side of the leg, over the soleus. In the middle of leg, both heads unite into one muscle, which tapers into a strong, thick tendon in the lower third of the leg; it is the Achilles tendon, with which it shares with the soleus muscle. This sturdy tendon is inserted into the posterior surface of the calcaneus (heel bone).
Action/function
Along with the soleus, it performs two important functions: 1) it performs plantar flexion of the foot, pointing the toes downwards, raising the heel off the ground as when we walk on tiptoe; 2) it contributes to the biceps femoris muscle in the flexion of the leg backwards and upwards at the knee-joint.
Innervation
The gastrocnemius muscle is supplied by the tibial nerve, which is a branch of the sciatic nerve.
Blood Supply
It receives oxygen-rich blood from the posterior tibial and peroneal artery.
Below, image of posterior side of right leg, showing its superficial muscles: the gastrocnemius and the soleus, with the Achilles tendon, which joins them together at the heel.
