|Origin||superior to articular surfaces of lateral condyle of femur and medial condyle of femur|
|Insertion||tendo calcaneus (achilles tendon) into mid-posterior calcaneus|
|Nerve||tibial nerve from the sciatic, specifically, nerve roots S1–S2|
|Actions||plantar flexes foot, flexes knee|
|Antagonist||Tibialis anterior muscle|
|Anatomical terms of muscle|
In humans, the gastrocnemius muscle (// or //; plural gastrocnemii; Latin, from Greek γαστήρ "stomach" and κνήμη (knēmē) "leg"; meaning "stomach of leg", referring to the bulging shape of the calf) is a very powerful superficial bipennate muscle that is in the back part of the lower leg. It runs from its two heads just above the knee to the heel.
The gastrocnemius is located with the soleus in the posterior (back) compartment of the leg. The lateral head originates from the lateral condyle of the femur, while the medial head originates from the medial condyle of the femur. Its other end forms a common tendon with the soleus muscle; this tendon is known as the calcaneal tendon or Achilles Tendon and inserts onto the posterior surface of the calcaneus, or heel bone.
Deep to the gastrocnemius (farther from the skin) is the soleus muscle. Some anatomists consider both to be a single muscle, the triceps surae or "calf muscle", since they share a common insertion via the Achilles tendon. The plantaris muscle and a portion of its tendon run between the two muscles, which is involved in "locking" the knee from the standing position. Since the anterior compartment of the leg is lateral to the tibia, the bulge of muscle medial to the tibia on the anterior side is actually the posterior compartment. The soleus is superficial to the mid-shaft of the tibia.
The gastrocnemius is primarily involved in running, jumping and other "fast" movements of leg, while to a lesser degree involved in walking and standing. This is due to the large degree of white muscle fibers present in the gastrocnemius. This is as opposed to the soleus, which has a larger degree of red muscle fibers and is the primarily activated muscle during the action of standing still, as has been through EMG studies.
A severe ankle dorsiflexion force may result in an injury of the muscle, commonly referred to as a "torn" or "strained" calf muscle, which is acutely painful and disabling.
Anatomical abnormalities involving the medial head of gastrocnemius muscle result in popliteal artery entrapment syndrome.
|Wikimedia Commons has media related to Gastrocnemius muscle.|
- -275120049 at GPnotebook
- Origin, insertion and nerve supply of the muscle at Loyola University Chicago Stritch School of Medicine
- Anatomy photo:14:st-0405 at the SUNY Downstate Medical Center