What allows bones to move?

What is the main type of joint?
(e.g. the Knee)

What joins bones to other bones?

What are two features of a ligament?

What joins bones to muscles?

What stops bones from rubbing together?

What is another other use of cartilage?

What lubricates the joints?

What releases synovial fluid?

What is the use of the circulatory system?

What is the heart's use?

What type of circulatory system do humans have?