The Circulatory System

The Circulatory System Blood Red blood cells Haemoglobin - red, carries oxygen Disc shaped, thinner at the centre No Nucleus White blood cells Contain a nucleus No definitive shape Protect against disease Platelets Tiny fragments of cells No nucleus Cause blood to clot Functions of blood Transport Defence against disease Blood Vessels Artery Carry blood from the heart Narrow lumen Thick walls High Pressure (Fast movement of blood) No valves Vein Carry blood back to the heart Wider lumen Thinner walls Low Pressure (Slow movement of blood) Valves to stop back-flow of blood Capillary Tiny blood vessels Walls one cell thick Substances pass into blood through capillaries

The Heart Blood enters through the Vena cava to the Right atrium Is pumped through the pulmonary artery to the lungs Returns from the lungs in the Pulmonary vein Is pumped around the body through the aorta Valves prevent blood from flowing backwards Normal heartbeat rate is 70bpm Increases during exercise as the body needs more energy. Normal body temperature is 37° Celsius