01:119:115 Lecture 24: Biology- Lecture 24 (Circulation - Chapter 42.1 - 42.3)
13 Jul 2016
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All animals need to exchange substances with their environment = nutrients, o 2, and wastes (example: co2) ultimately occurs by diffusion into and out of cells. Problem = diffusion is very slow over long distances. Some animals do not have a circulatory system don"t need it: flatworm flat body efficient diffusion, cnidarians gastrovascular cavity brings nutrients close to cells, nematodes fluid in pseudocoelom helps circulate materials. Animals with many layers of cells (especially if terrestrial) need a circulatory system. Circulatory system has 3 basic components: a circulatory fluid, a set of interconnecting vessels, a muscular pump = heart. Circulatory system connects interstitial fluid with the organs that: Low pressure relatively inefficient but, less costly in energy expenditure. Thursday, april 16, 2015: closed circulatory system, blood = circulatory fluid inside vessel distinct from interstitial fluid, heart (or hearts): pump blood into large vessels branch into smaller infiltrate organs. Higher blood pressure = more efficient important in larger & more active animals.
