Surae) is located in the posterior leg group and is mainly composed of gastrocnemius muscle and soleus muscle.

Morphology: Its two heads are called gastrocnemius muscle in the shallow layer, and the other head is soleus muscle in the deep layer.

Starting point and stopping point: the medial and lateral heads of gastrocnemius muscle start from the medial and lateral condyles of femur and move to the tendinous structure at the midpoint of calf; The soleus muscle originates from the upper back of tibia and fibula and the soleus muscle line of tibia, and the muscle bundle moves downward into tendon. The three heads meet, forming a swollen calf at the upper part of the calf, continuing down to the achilles tendon and ending at the calcaneal tubercle.

Function: Bend the calf and lift the heel. When standing, it can fix the ankle joint and knee joint to prevent the body from falling forward.

Nerve innervation: It is mainly innervated by tibial nerve (L4~S3).