Unicellular organisms such as Amoeba has a large surface area to volume ratio (SA:V) where substances move short distances by diffusion. Multicellular organisms on the other hand have a small (SA:V) ratio. where substances move a longer distance. Since multicellular organisms are so complex, they require a system to help transport substances much faster. This system is called the Human Circulatory System. This system transports both wasteful and useful substances such as: Water, oxygen, Carbon dioxide, digested food, ammonia, Glucose, Hormones etc.
The circulatory system is made up of three main components 1.The heart, 2.The blood and 3.Blood vessels.
Blood
Blood has 3 main components : Plasma, Red blood cell , White blood cell and platelets. Plasma has 90% water and 10% dissolved substances. Red blood cells transport O2 and CO2 gas to and from the lungs and body. White blood cells are part of the immune system, helping to fight infections or diseases.
Blood Vessels
These are tubes carrying blood to and from the heart around the body its made up of arteries, veins and capillaries. Arteries carries oxygenated blood away from the heart, arterioles branches into a network of capillaries that run throughout the organ, while veins join from the capillaries leading deoxygenated blood to the heart. What are the capillaries function?
Heart
The heart acts like an engine, pumping blood through the blood vessels around the body. It has 4 chambers, 2 small atrium and 2 large ventricles. While the right side pumps deoxygenated blood to the lungs, the left side pumps oxygenated blood to the body.
