CHAPTER 42
                  CIRCULATION AND GAS EXCHANGE

I. Circulation in Animals
•A.Cnidarians and flatworms have a ga...
A. The double circulation of the mammalian cardiovascular system includes the
pulmonary (lung) circuit and the systemic(bo...
m or so.
Chapter 42
Chapter 42
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Chapter 42

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Chapter 42

  1. 1. CHAPTER 42 CIRCULATION AND GAS EXCHANGE I. Circulation in Animals •A.Cnidarians and flatworms have a gastrovascular cavity. •This is an opening in the center of the body which serves for digestion and distribution of substances. • B. In arthropods and most mollusks, blood bathes organs directly in an open circulatory system. • There is no distinction between blood and interstitial fluid, collectively called hemolymph. • C. In a closed circulatory system, as found in vertebrates, blood is confined to vessels. • One or more hearts pump blood into large vessels that branch into smaller ones coursing through organs. • D. Vertebrate phylogeny is reflected in adaptations of the cardiovascular system •1.The circulatory system of vertebrates is called the cardiovascular system. •The heart consists of one atrium or two atria, the chambers that receive blood returning to the heart, and one or two ventricles, the chambers that pump blood out of the heart. • 2. Arteries, veins, and capillaries are the three main kinds of blood vessels. • a.Arteries carry blood away from the heart toward capillaries. • Blood is pumped from the ventricle to the gills (the gill circulation) where it picks up oxygen and disposes of carbon dioxide across the capillary walls. • The ventricle pumpsblood into a forked artery that splits the ventricle’s output into the pulmocutaneous and systemic circulations. • Reptiles also have double circulation with pulmonary (lung) and systemic circuits. • KEY POINT!--The evolution of a powerful four-chambered heart was an essential adaptation in support of the endothermic way of life characteristic of birds and mammals.
  2. 2. A. The double circulation of the mammalian cardiovascular system includes the pulmonary (lung) circuit and the systemic(body) circuit • The left ventricle pumps oxygen-rich blood out to the body tissues through the systemic circulation. B.A cardiac cycle is a complete sequence of pumping, (contraction), and filling, (relaxation). Blood is a connective tissue with cells suspended in plasma •Blood is a specialized connective tissue consisting of several kinds of cells suspended in a liquid matrix called plasma. C. Cardiovascular diseases are the leading cause of death in the US. •The final blow is usually a heart attack or stroke. •A heart attack is the death of cardiac muscle tissue resulting from prolonged blockage of one or more coronary arteries, the vessels that supply oxygen-rich blood to the heart. •A stroke is the death of nervous tissue in the brain. II. Gas exchange supplies O2 for cellular respiration and disposes of CO2. •Gas exchange is the uptake of oxygen (O ) and the discharge of carbon dioxide 2 (CO2). A. Gills are respiratory adaptations of most aquatic animals Gills are outfoldings of the body surface that are suspended in water. B. Tracheal systems and lungs are respiratory adaptations of terrestrial animals •As a respiratory medium, air has many advantages over water. • C. Most reptiles and all birds and mammals rely entirely on lungs for gas exchange. • Turtles may supplement lung breathing with gas exchange across moist epithelial surfaces in their mouth and anus • Air enters through the nostrils and then enters the larynx. • At their tips, the tiniest bronchioles dead-end as a cluster of air sacs called alveoli. • A diversity of respiratory pigments has evolved in various animal taxa to support their normal energy metabolism. • One example, hemocyanin, found in the hemolymph of arthropods and many mollusks, has copper as its oxygen-binding component, coloring the blood bluish. Deep-diving air-breathers stockpile oxygen and deplete it slowly •When an air-breathing animal swims underwater, it lacks access to the normal respiratory medium. Most humans can only hold their breath for 2 to 3 minutes and swim to depths of 20
  3. 3. m or so.

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