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Lecture Notes Chapter 42

Lecture Notes Chapter 42 - Lecture Notes Chapter 42...

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Lecture Notes Chapter 42: Circulation and gas exchange Every organism must exchange materials with its environment and this exchange ultimately occurs at the cellular level In unicellular organisms these exchanges occur directly with the environment For most of the cells making up multicellular organisms direct exchange with the environment is not possible These organisms have evolved systems for material transport and exchange Most complex animals have internal transport systems These circulate fluid, providing a lifeline between the aqueous environment of living cells and the exchange organs, such as lungs, that exchange chemicals with the outside environment Gastrovascular cavities In the simplest organisms only The limited efficiency restrict the size of these animals! Open and closed circulatory systems More complex animals have one of two types of circulatory systems: open or closed Both of these types of systems have three basic components A circulatory fluid (blood) A set of tubes (blood vessels) A muscular pump (the heart) Insects and many other invertebrates have open circulatory systems Heart accepts hemolymph through ostiae, then pumps it anteriorly Insects do not transport gas via their hemolymph, only nutrients, thus the reduced need for an efficient circulatory system Vertebrate circulatory systems Closed system, for transport of both nutrients and dissolved gases Central heart with 2-4 chambers In advanced vertebrates, the oxygenated blood is kept separated from the deoxygenated blood Blood vessels returning to the heart are called veins Blood vessels leading blood from the heart to the organs are arteries Arteries and veins have a distinct anatomy and morphology! Arterial blood flowing FROM the heart to the organs is oxygenated (bright red) Venous blood returning from the organs TO the heart is de-oxygenated (dark red) Fishes A fish heart has two main chambers One ventricle and one atrium Blood pumped from the ventricle Travels to the gills, where it picks up O 2 and disposes of CO 2 1
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Amphibians Frogs and other amphibians Have a three-chambered heart, with two atria and one ventricle The ventricle pumps blood into a forked artery That splits the ventricle’s output into the pulmocutaneous circuit and the systemic circuit Reptiles (Except Birds) Reptiles have double circulation With a pulmonary circuit (lungs) and a systemic circuit Turtles, snakes, and lizards Have a three-chambered heart Mammals and Birds In all mammals and birds The ventricle is completely divided into separate right and left chambers The left side of the heart pumps and receives only oxygen-rich blood While the right side receives and pumps only oxygen-poor blood A powerful four-chambered heart Was an essential adaptation of the endothermic way of life characteristic of mammals and birds Mammalian Circulation: The Pathway
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