Circulatory system is the first organ system to become functional during development. Development of heart: On each side of embryo, an aorta forms ventrally and swings dorsally. The paired aortae in ...

Red blood cell Carry oxygen. Contain haemoglobin (rich in iron) to carry oxygen. Biconcave shape to provide a large surface area for the diffusion of oxygen. No nucleus to provide more space for ...

blood a pump (the heart) to push the blood around the body a system of tubes to contain the blood (arteries, veins and capillaries) The blood is the transport medium – it carries substances to ...