Explore the body's basic functions and the key vitamins for optimum health. Including the immune system which is the body's defence against infection and disease. The heart and circulatory system, also known as the cardiovascular system, which is the body's network that delivers blood to the various tissues in the body. The nervous system which is essential to the way we think, learn, move and behave. Then lastly the musculoskeletal system which comprises of our bones, joints and muscles and is integral to all movement in the human body.