The heart pumps some blood to the lungs and some blood to the rest of the body each time it beats. The blood on the left side is kept separate from the blood on the right side. This is called double circulation and is efficient way of delivering oxygen to the tissues than single circulation.Blood enters the heart through a vein and collects in an atrium. The atrium is emptied into a ventricle which contracts to put the blood under pressure. The blood is forced out through an artery as a valve prevents it flowing back to the atrium. The artery also contains a valve to stop blood flowing back to the ventricle when the ventricle relaxes.

Arteries carry blood from the heart to the lungs and the rest of the body. The thick muscular wall can withstand the high pressure of blood as it leaves the heart. They branch to become cappillaries. Capillaries take blood to and from every cell . The one cell thick wall allows oxegon to go through and oxegenate the blood quickly and easily.Capillaries then join together to become veins. The veins then carry blood back to the heart. The thin layer of muscle allow them to be squashed and to push the blood upwards. Valves in the veins then stop the blood going back again.

There are a lot of these and are known to be red however it is the haemoglobin that gives them this colour . oxegon is added in the lungs then oxegon is realeased in the tissue

Found throughout the body, including the blood and lymphatic system. unlike other blood cells they have nuclei. They are used in defending the body from diseases by sending out antibodies to attach to the antigen. After this another white blood cell will come and ENGULF that antibody. They can then after they have killed the antibodies go. However some turn into MEMORY CELLS and then if that same antibody returns they can kill it rapidly. An example of this is chicken pox... after the first time they won't affect the body again because of the memory cells.

a small colourless disc shaped cell fragment without a nucleus, found in large numbers in blood and involved in clotting.Platelets are tiny blood cells that help your body form clots to stop bleeding. If one of your blood vessels gets damaged, it sends out signals that are picked up by platelets. The platelets then rush to the site of damage and form a clot to repair the damage.The process of spreading across the surface of a damaged blood vessel to stop bleeding is called adhesion. This is because when platelets get to the site of the injury, they grow sticky tentacles that help them adhere. They also send out chemical signals to attract more platelets to pile onto the clot in a process called aggregation.

haemoglobin bonds with oxegon to make oxyhaemoglobin as it passes through the lungs. oxegon is then realeased into tissue.

contains water, salts, enzymes, antibodies and other proteins. 90% water. it can transport carbon dioxide, digested food, urea, hormones and heat