Chapter 42

1. Chapter 42 Circulation and Gas Exchange

2. Overview: Trading with the Environment • Every organism must exchange materials with its environment • Exchanges ultimately occur at the cellular level

3. In unicellular organisms, these exchanges occur directly with the environment • For most cells making up multicellular organisms, direct exchange with the environment is not possible • A salmon’s feathery gills are an example of a specialized exchange system in animals

5. Concept 42.1: Circulatory systems reflect phylogeny • Transport systems connect the organs of exchange with the body cells • Most complex animals have internal transport systems that circulate fluid

6. Invertebrate Circulation • The wide range of invertebrate body size and form is paralleled by diversity in circulatory systems

7. Gastrovascular Cavities • Simple animals, such as cnidarians, have a body wall only two cells thick that encloses a gastrovascular cavity • This cavity functions in both digestion and distribution of substances throughout the body • Some cnidarians, such as jellyfish, have elaborate gastrovascular cavities

9. Circular canal LE 42-2 Radial canal Mouth 5 cm

10. Open and Closed Circulatory Systems • More complex animals have either open or closed circulatory systems • Both systems have three basic components: • A circulatory fluid (blood or hemolymph) • A set of tubes (blood vessels) • A muscular pump (the heart)

11. Heart Heart LE 42-3 Hemolymph in sinuses surrounding organs Interstitial fluid Small branch vessels in each organ Lateral vessel Anterior vessel Ostia Dorsal vessel (main heart) Tubular heart Auxiliary hearts Ventral vessels An open circulatory system. A closed circulatory system.

12. Heart Hemolymph in sinuses surrounding organs Lateral vessel Anterior vessel Ostia Tubular heart

13. In insects, other arthropods, and most molluscsblood bathes the organs directly in an open circulatory system • There is no distinction between blood and interstitial fluid, and this general body fluid is more correctly called hemolymph

15. In a closed circulatory system, blood is confined to vessels and is distinct from the interstitial fluid • Closed systems are more efficient at transporting circulatory fluids to tissues and cells • Oxygen travels via hemoglobin on blood cells

16. Survey of Vertebrate Circulation • Humans and other vertebrates have a closed circulatory system, often called the cardiovascular system • Blood flows in a closed cardiovascular system, consisting of blood vessels and a two- to four-chambered heart

17. Arteries carry blood AWAY from the heart and to capillaries, the sites of chemical exchange between the blood and interstitial fluid • Veins return blood from capillaries INTO the heart • Capillaries are very thin to allow gas exchange to occur

19. Coronary blood vessels: provides the constant supply of oxygen and nutrients needed by the heart

20. 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 O2and disposes of CO2

22. Amphibians • Frogs and other amphibians have a three-chambered heart: 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

23. 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

25. Mammals and Birds • In all mammals and birds, the ventricle is 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

26. A powerful four-chambered heart was an essential adaptation of the endothermic way of life characteristic of mammals and birds

27. FISHES AMPHIBIANS REPTILES (EXCEPT BIRDS) MAMMALS AND BIRDS LE 42-4 Gill capillaries Lung and skin capillaries Lung capillaries Lung capillaries Pulmocutaneous circuit Pulmonary circuit Gill circulation Pulmonary circuit Right systemic aorta Artery Heart: Ventricle (V) Left systemic aorta A A A A A A Atrium (A) V V V V V Right Left Left Right Right Left Systemic circulation Systemic circuit Systemic circuit Vein Systemic capillaries Systemic capillaries Systemic capillaries Systemic capillaries Systemic circuits include all body tissues except lungs. Note that circulatory systems are depicted as if the animal is facing you: with the right side of the heart shown at the left and vice-versa.

28. Concept 42.2: Double circulation in mammals depends on the anatomy and pumping cycle of the heart • The human circulatory system serves as a model for exploring mammalian circulation

29. Mammalian Circulation: The Pathway • Heart valves dictate a one-way flow of blood through the heart • Blood begins its flow with the right ventricle pumping blood to the lungs • In the lungs, the blood loads O2 and unloads CO2 • Oxygen-rich blood from the lungs enters the heart at the left atrium and is pumped to the body tissues by the left ventricle • Blood returns to the heart through the right atrium

30. Capillaries of head and forelimbs Anterior vena cava Pulmonary artery Pulmonary artery Aorta Capillaries of right lung Capillaries of left lung LE 42-5 Pulmonary vein Pulmonary vein Right atrium Left atrium Left ventricle Right ventricle Posterior vena cava Aorta Capillaries of abdominal organs and hind limbs

31. Animation: Path of Blood Flow in Mammals

32. a b’ b’ c b e e o e e i m q h L L L g L f h L d a TO UPPER BODY FROM UPPER BODY TO LUNGS TO LUNGS FROM LUNGS FROM LUNGS Aorta Left Atrium Pulmonary Arteries Right Atrium Superior Vena Cava Aorta Pulmonary Veins Pulmonary Veins Left Ventricle Right Ventricle FROM LOWER BODY Inferior Vena Cava TO LOWER BODY