BIO 121 Lecture Notes - Lecture 21: Heart Valve, Aorta, Pulmonary Circulation
24 Jul 2020
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Circulatory sys req b/c oxygen/nutrients/hormones need to be transported around body. Have pipes carry transport fluid ; have pumps force fluid around body. Blood (haemolymph) flows freely within body cavities direct contact /w internal tissues/organs. Fluid leaves vessels to trickle thru tissues. Fluid returns to heart enters through openings (ostia) acts as valve. Specific components leak out of the vessels: only low molec weight solutes + water leave vessels, transport fluid kept separate from fluid that surrounds cells. Faster transport & more efficient delivery of fluid to tissues. Controls blood distribution by changing vessel resistance. Keeps freshly oxygenated blood separate from deoxygenated blood (imp to ensure delivery of right type of blood req) Before this, simple diffusion across simple organisms like amoeba & then open circulatory system in insects. Under low pressure blood pumped over gills to become oxygenated hence low pressure in capillary beds not efficient delivery of nutrient/oxygen delivery. Change in heart structure partial division in atrium.
