Circulation

• Multicellular organisms require transport systems to supply their cells and remove waste products.
• In humans, one of the functions of the circulatory system is to transport substances.
• The circulatory system consists of the heart, blood vessels, and white blood cells.
• Development of cardiovascular disease can be evaluated through taking pulses and calculating blood flows.
• The complete circulation: One-way flow
• Blood must flow one way only through the circulatory system.
• Valves in the heart close to ensure this one-way flow.
• Closure of a valve prevents back flow.
• Faulty heart valves can be replaced with a biological valve from a human donor or made from animal tissue from a pig or cow.
• Mechanical valves last longer, but blood can clot on them.
• A patient may need long-term medication that prevents blood clots developing.
• Biological valves are more likely to wear out.