Explain how the human circulatory system is adapted to supply oxygen to the tissues and remove waste products from tissues.

This is an example of knowledge recall question with need for further explanation. It is therefore important to be able to explain yourself concisely and in the manner that the examiners expect to gain the maximum amount of marks. In regards to the circulatory system, each adaption is there to maximize the flow of blood to tissues, and to increase the area available for exchange of substances once the blood reaches those tissues. For this question it would be most beneficial to move through the process of the circulatory system and then discuss each present adaption.The Human circulatory system is a duel circulatory system. This means that there are two separate channels for oxygenated blood and deoxygenated blood. This means that overall the blood within the system is under a higher pressure and therefore there is a greater flow of blood to the tissue. The heart made of specialized cardiac muscle cells which have long protein filaments that can slide past each other. This allows the muscle cell to shorten which brings about a contraction to pump blood. Once the heart has pumped, deoxygenated blood leaves the heart through the pulmonary artery to the lungs so that the oxygen can diffuse into the blood through the alveoli. The blood then returns to the the heart through the pulmonary vein where it is then moved into the body through the aorta. Arteries then carry blood from the heart to tissues where capillaries deliver oxygen to cells for respiration and then subsequent energy release. The large surface areas and thickness of the of the capillaries (1 cell thick) allows for maximum exchange of substances. Any waste products then transfer back into the blood by diffusion across the capillary. The deoxygenated blood then moves back to the heart through veins, which contain valves to the stop backflow. This is because the deoxygenated blood is under a lower pressure. Blood contains specialized red blood cells which have a biconcave shape and contain the molecule haemaglobin to bind oxygen; they don't have a nucleus to maximize the space available for binding oxygen.