Explain how the human circulatory system is adapted to: • supply oxygen to the tissues • remove waste products from tissues – 7013

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1. he circulatory system is a double circulatory system. This means that blood passes through the heart twice for each complete circuit of the body. This helps to keep blood pressure high and allows efficient delivery of oxygen to tissues.

   The heart is made of cardiac muscle, which has special protein filaments that slide over each other to make the muscle contract and pump blood. Blood is pumped from the heart to the lungs through the pulmonary artery. In the lungs, oxygen diffuses into the blood from the alveoli.

   Oxygen is carried by red blood cells, which contain haemoglobin. The red blood cells have no nucleus, giving more space to carry oxygen. Oxygenated blood returns to the heart via the pulmonary vein and is then pumped around the body through the aorta.

   Capillaries deliver oxygen to cells for respiration, and carbon dioxide (a waste product) diffuses back into the blood plasma. Capillaries have thin walls and a large surface area to make gas exchange more efficient.

   Veins return blood to the heart. They have valves to prevent backflow of blood. Cardiac output can change depending on the body’s needs, such as during exercise, and is affected by hormones like adrenaline.

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