16. Endothelial cells makes up what on all vessels? Which vessel has the most muscle and why? Which contains the majority of blood? Which has valves and why? What controlsblood flow into capillaries? Where does exchange take place?17. Myocardium consists of what? Which layer of the pericardium is closest to the heart andwhich is on the outside of the structure? What role does the pericardial sac have?18. Which chambers in the heart have to pump the hardest? Why? What is the stroke volume?19. Comparing the atria to ventricles, which chambers have to pump the hardest? Why?20. Which represents the correct sequence of parts through which blood moves in passing from the vena cava to the lungs? From the lungs to the systemic circuit?
21. What part of the heart consists of self-exciting tissue and is called the heart's pacemaker?22. The SA node is referred to as what? Where is it located?23. What is the function of the valves in the heart?24. How is backflow of blood prevented?25. The aorta is situated where in the flow of blood?26. What is the aorta's location in the flow of blood? It receives it from where and delivers it to where? Is the blood oxygenated?27. The right atrium is situated where in the flow of blood?