Gastrocnemius muscle 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. Further, it is considered a superficial muscle as it is located directly under skin, so its shape is clearly visible in a normal human being. 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 "three-headed [muscle] of the calf", since they share a common
Artificial bone which is one of the most stable forms of calcium phosphate, makes up about 60 to 65 percent of the bone. The rest of the bone is composed of materials including chondroitin sulfate, keratan sulfate and lipid. Increased research and knowledge regarding the organization, structure of properties of collagen and hydroxyapatite have led to many developments in collagen-based scaffolds in bone tissue engineering. The structure of hydroxyapatite is very similar to that of the original bone, and collagen can act as molecular cables and further improve the biocompatibility of the implant. In the United States, more than 6.5 million bone