“The structures of body systems are determined by their functions”. Discuss this statement, focussing on the Circulatory System. You should include diagrams and relevant examples in your essay. In order to survive it is necessary for every cell in the body to exchange materials as not all cells are in contact with the external environment; we rely on the circulatory system to do this which is composed of the heart, blood vessels and blood. The heart consists of four chambers two atria and two ventricles it also has two pairs of valves (atrioventricular valves and the semilunar valves). The arteries, arterioles, veins and venules have the same tissue layout but different thickness of the tissues is different. It also contains nervous tissue which is under the control of autonomic nervous system controlling whether the heart beat speeds up or slows down. In arteries there is a thicker smooth muscle layer to resist bursting. The blood is made up of plasma a fluid matrix and different types of cells; the function of the blood is to transport substances needed to carry out cellular functions, protection by clotting and regulation the circulatory system transport hormones around the body. In humans there is a double circulatory system, with left atrium receives oxygenated blood from the lungs and it is pumped to the rest of the body. The other receives deoxygenated blood from the rest of the body and it is pumped to the lungs. The heart in which the blood is delivered too is a two cycle pump; the blood returns via the atria where the pressure increases causing the atrioventricular valves (AV) to open filling the ventricles about 80% the atria contraction fills the remaining 20%. After a slight delay contraction of the ventricles happens causing AV valves to close the pressure in ventricles now forces the semilunar valves to open allowing blood to flow into the arterial system. The heart is made up of heart muscle with the left side having a thicker muscular wall as it...
References: Raven et al. (2008).Biology, Eight Edition: McGraw-Hill
"Structure and Function of Red Blood Cells and White Blood Cells." 123HelpMe.com. 30 Oct 2011
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