Human leg
| Human leg | |
|---|---|
 Lateral aspect of right leg | |
| Details | |
| Identifiers | |
| Latin | membrum inferius |
| FMA | 7184 |
| Anatomical terminology | |
The human leg is the lower limb of the human body, including the thigh, knee, lower leg, ankle, foot, or sometimes even the hip or buttock region. There are thirty bones in each leg. The major bones are the femur (thigh bone), tibia (shinbone), and adjacent fibula.
The part of the leg between the hip and the knee is called the thigh. The part between the knee and the ankle is called the lower leg, shank, crus, or in anatomy simply the leg.[1] The lower leg includes the shin in the front and the calf at the back.[2]
Legs are used for standing, many forms of human movement, recreation such as dancing, and constitute a significant portion of a person's mass. Evolution has led to the human leg's development into a mechanism specifically adapted for efficient bipedal gait.[3] While the capacity to walk upright is not unique to humans, other primates can only achieve this for short periods and at a great expenditure of energy.[4] In humans, female legs generally have greater hip anteversion and tibiofemoral angles, while male legs have longer femur and tibial lengths.[5]
Structure
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In human anatomy, the lower leg or crus (or shank) is the part of the lower limb that lies between the knee and the ankle.[6][2] In the lower leg, the calf is the back portion, and the tibia or shinbone together with the smaller fibula make up the shin, the front of the lower leg.[7] Anatomists restrict the term leg to this use, rather than to the entire lower limb.[8] The thigh is between the hip and knee and makes up the rest of the lower limb.[2] The term lower limb or lower extremity is commonly used to describe all of the leg.
Evolution has provided the human body with two distinct features: the specialization of the upper limb for visually guided manipulation and the lower limb's development into a mechanism specifically adapted for an efficient bipedal gait.[3] While the capacity to walk upright is not unique to humans, other primates can only achieve this for short periods and at a great expenditure of energy.[4]
The human adaption to bipedalism has also affected the location of the body's center of gravity, the reorganization of internal organs, and the form and biomechanism of the trunk.[9] In humans, the double S-shaped vertebral column acts as a great shock-absorber which shifts the weight from the trunk over the load-bearing surface of the feet. The human legs are exceptionally long and powerful as a result of their exclusive specialization for support and locomotion—in orangutans the leg length is 111% of the trunk; in chimpanzees 128%, and in humans 171%. Many of the leg's muscles are also adapted to bipedalism, most substantially the gluteal muscles, the extensors of the knee joint, and the calf muscles.[10]