1. The Cardiovascular System SBI3U: Internal Systems

2. Open circulatory systems greatly increase the efficiency of transport of substances within a body relative to diffusion

3. Closed circulatory systems are even more efficient than open circulatory systems Fig. 42.3

4. In vertebrates: Circulatory system + gas exchange organs = cardiovascular system

5. Fish have 2-chambered hearts A single circuit with 2 sets of capillaries, which limits the maximum aerobic metabolic rates of fishes

6. Fish have 2-chambered hearts Gill capillaries are the sites of gas exchange with the environment

7. Amphibians have 3-chambered hearts Three chambers allows for double circulation, i.e., two circuits, such that blood passes through a single set of capillaries in each round-trip from and back to the heart

8. Amphibians have 3-chambered hearts In most amphibian larvae, the capillaries of the pulmocutaneous circuit are found in gills

9. Amphibians have 3-chambered hearts However, most adult amphibians exchange gases through lungs and their skin

10. Mammals have 4-chambered hearts

13. Systemic Pulmonary

14. Heart valves prevent backflow of blood

15. Blood flows out of and away from the ventricular chambers via arteries

16. Arteries have thick walls whose elasticity helps keep blood moving

17. Arteries branch into arterioles

18. Arterioles branch into capillaries

19. Gas exchange occurs across capillaries, whose walls are one cell thick

20. We have 50,000 miles of them Red blood cells Capillary wall Few human cells are > 100 μm from a capillary

21. Capillaries connect to venules

22. Venules connect to veins

23. Veins have valves that help prevent backflow