The skeleton is a tough, flexible framework for the rest of your body. It also has other functions. It stores [?] such as calcium and phosphorus. It makes red blood cells, platelets, and some [?] blood cells in the bone marrow. It also forms a system of levers with muscles attached. This enables the body to move. It also protects internal [?].

[?] hold the bones to each other, [?] attach muscle to bone. A muscle pulls one of the bones, which moves the joint. The [?] fluid lubricates and nourishes the tissues in the joint capsule. The synovial [?] lines the joint capsule and secretes synovial fluid. The [?] is a smooth protective surface which protects ther ends of the bones.

Muscles cannot push, the can only pull. The muscles [?] to pull. They only stretch when another muscle pulls. The arm is bent when the [?] muscles contract, and the [?] muscles stretch. When the arm straightens the [?] contract and the [?] muscles stretch.

The upper arm has a bone called the [?]. The lower arm has two bones. The upper bone is called the [?], and the lower one is called the [?]. The upper bone in the leg is called the [?], and the lower bones of the leg are called the tibia and [?].

Weight-bearing activities such as jogging stimulate bone growth. Inactivity can maker bones much less dense and [?].




Some athletes take muscle building supplements which are banned. Many of the banned substances are [?]. These can have serious health effects on the body, and have an unfair [?] over other athletes in competions.