Understanding Circulation and Gas Exchange in Animals

1. Chapter 42 Notes Circulation and Gas Exchange

2. Exchange of Materials • Simple animals with few cell layers can operate by diffusion alone. -Cnidarians take in materials into their gastrovascular cavity and material diffuse outward.

3. Animals with many cell layers require more than a branching gastrovascular cavity. • Open circulatory system • Absence of vessels • No distinction between blood and other fluids (hemolymph) • Drawn into heart through ostia • Pumped out into spaces surrounding organs

4. Closed Circulatory System • Presence of vessels • Some annelids, mollusks, and vertebrates

5. Circulation in Humans • Arteries • Large vessels found near the aorta of the heart. • Are able to receive high pressure bursts of blood from the heart. • Arterioles -Smaller and less muscular than arteries. • Capillaries • Smallest blood vessels. • Their walls are often only one cell thick with no muscle. • Allow gases to pass in and out of the blood stream.

6. Venules • Have a porous wall (containing holes) that allows fluids and white blood cells to pass through. • White blood cells will gather on damaged tissues causing inflammation. • Veins • At any given time, they contain 65% of the body’s blood. • Contain some muscle. • Have valves that prevent blood from flowing backward.

9. Variations in Animals • Fish Circulation • One atrium, one ventricle • Single circuit between gill and systemic capillaries

10. Amphibian Circulation • Two Atria, one ventricle • Two circuits (double circulation) 3. Pulmocutaneous-from heart to skin and lungs • Systemic-to capillary beds of the body

11. Mammalian Circulation • Crocodiles, birds, mammals • Two atria, two ventricles • Two circuits • Pulmonary • Systemic • To electrochemical locations • Pacemaker -sinoatrial node (SA) -located on anterior end of right atria -innervates both atria • Atrioventricular node (AV) -stimulates both ventricles -stimulated by SA node

13. Variation in Respiratory Surfaces • Gas exchange occurs via diffusion (influenced by pressure) • Ideal tissues must be • Thin • Moist • Have large surface area • Phylums Porifera and Cnidaria -Exchange occurs throughout the entire surface

14. Phylums Platyhelminthes and Annelida • Exchange occurs at skin • Utilize hemoglobin • Phylum Arthropoda • Gas enters through spiracles • Passes through system of tracheal tubes • Arthropods and Mollusks use hemocyanin -Copper in place of Iron

15. Aquatic Organisms • Exchange takes place via gills • Utilize countercurrent exchange

16. Gas Exchange in Humans • Air passes through Pharynx  Larynx  Trachea  Bronchi  Bronchioles  Alveolar Sacs • Drawn in by negative pressure 3. Medulla monitors pH