Also known as the kneecap it articulates with the femur thigh bone. Here the benefits of dark skin are outweighed by the need for bone-strengthening vitamin D produced through exposure to UV rays. Longest Bone In Our Body Femur Health Facts Body Our Body The human body has 206 bones as a adult when you are born you have 300 bones. . The two primary lymphoid organs are the thymus and red bone marrow. The human body is composed of elements including hydrogen oxygen carbon calcium and phosphorus. Human bone is made in part of calcium particularly a form called hydroxylapatite. Skin is the human bodys largest organ. Secondary lymphatic organs include lymph nodes tonsils. All of these muscles are anchored throughout the largest bone present in the human body known as the femur. You will find questions suitable for children on the anatomy of the human body from organs and joints to bones and systems. The longest...