ch28BIOLOGY - CHAPTER 28 Circulation - The need for...

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CHAPTER 28 Circulation - The need for circulation (and circulatory systems) arose, as animals got larger. - Small (and thin) animals have all of their cells in close proximity to the outside environment. There is a very short distance that food and oxygen have to travel to get to the center of each cell. Likewise, the distance that waste and CO 2 have to travel to get out of the cell is also very short. - Materials (good or bad) can efficiently move over short distance in an organism by diffusion. Larger distances require some energy requiring process (active transport, circulation, etc.). - In larger animals since diffusion is not effective enough to get the good things (nutrients and oxygen) in and get the bad things (waste and carbon dioxide) out, circulation is required . - There are 2 types of circulatory systems (see fig 28-1): Open circulatory system Closed circulatory system Both types have three major parts: 1) A fluid that circulates (blood) open - part of the “channel” that the fluid circulates through is an open space within the body called the hemocoel (blood cavity) (see fig 28-1a) closed - the blood is usually confined (closed) in the vessels. 2) A channel (vessels) that the fluid circulates through 3) A pump (heart) to keep the fluid moving THE VERTEBRATE CIRCULATORY SYSTEM 7 major functions. The first three are common to all circulatory systems. 1) Transport of oxygen to the tissues 2) Transport of nutrients to the tissues 3) Transport of waste from the tissues Some of the next four are found only in vertebrates: 4) Distribution of hormones 5) Regulation of body temperature (homeostasis) 6) Prevention of blood loss (clotting) 7) Protection from invaders (immune system) The vertebrate heart is a muscular pump that has evolved in design over time (see fig 28-2) EVOLUTIONARY TREND IN HEART DESIGN Heart design Organisms 2-chambered heart 3-chambered heart amphibians and reptiles 4-chambered heart birds and mammals In all of these designs the heart chambers are either receiving blood ( atrium , plural atria ) from the body or sending the blood out ( ventricle ) into the body.
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THE FOUR-CHAMBERED HEART (see figs 28-3) right ventricle + left atrium - used for pulmonary circulation . - responsible for pumping blood to and receiving blood back from the lungs.
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This note was uploaded on 10/01/2010 for the course BIOL 1002 taught by Professor Pomarico during the Spring '08 term at LSU.

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ch28BIOLOGY - CHAPTER 28 Circulation - The need for...

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