15 - circulatory systems I

15 - circulatory systems I - BIO325H Circulatory Systems...

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BIO325H Circulatory Systems, Part I 2/20/08 Most animal species have a dedicated circulatory system whose function is to rapidly circulate body fluids, thereby insuring that all tissues have ready access to the exchange systems for O 2 /CO 2 and nutrients/wasteproducts. Some groups ( e.g. insects) have an ‘open’ circulatory system in which a single body fluid called hemolymph is pumped through the tissues and eventually returns to the heart. However, we will focus here on the ‘closed’ circulatory system found in vertebrates and a number of other animal taxa ( e.g. annelid worms). All circulatory systems share two basic structural features: a pumping organ, the ‘heart’, which contracts to generate hydrostatic pressure; and a series of vessels for transporting the pressurized fluid away from - and in closed circulation, back to - the heart. In today’s lecture we will focus on the evolution, anatomy, and physiology of the mammalian heart, followed in the next lecture by a closer examination of the vascular system. [Note: the adjective ‘vascular’ refers to the blood vessels. ] Learning Goals 1. In a closed circulatory system, what is the anatomical distinction between blood and interstitial fluid? What is distinct about the components (chemical and cellular) of these two fluids? 2. You should be completely familiar with the anatomy of the human heart, and the pathway of blood flow through it [ see Sadava, Fig. 49.2 ]. Why does blood flow through the heart in only one direction? 3. What is different about the anatomy of the cardiovascular system in a fish vs. a mammal or bird? Why are mammals and birds said to have 'double circulation'? In each species, how many times must a blood cell pass through the heart to return to the same exact location? Why is double circulation more efficient than the single circulation found in fish? 4. What is the meaning of the terms ‘systole’ and ‘diastole’? Your book only refers to systole and diastole in the ventricles, and you must understand that there is also a third phase in the cardiac cycle called atrial systole. On the next page of the posted handout, I have included a modified version of Purves, Fig. 49.4, showing all of the phases of the cardiac cycle. 5. You should learn and be able to explain what is happening to the heart and the blood flow during
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15 - circulatory systems I - BIO325H Circulatory Systems...

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