Circulatory system

3. Structures in veins and the heart that prevent the backflow of blood and ensure one-way circulation.
5. The middle layer of blood vessels, composed of smooth muscle and elastic fibers, regulating blood pressure and flow.
6. The largest artery in the body that distributes oxygenated blood from the left ventricle to the rest of the body.
8. A blood vessel that carries oxygenated blood away from the heart under high pressure.
12. The rhythmic expansion and recoil of an artery with each heartbeat, reflecting heart rate.
13. Referring to the lungs; the pulmonary artery carries deoxygenated blood to the lungs, and the pulmonary vein carries oxygenated blood to the heart.
14. An upper chamber of the heart that receives blood from veins and pumps it to the ventricles.
15. The smallest blood vessel where gas and nutrient exchange occurs between blood and tissues.

1. A lower chamber of the heart that pumps blood into arteries for circulation.
2. A blood vessel that carries deoxygenated blood back to the heart, often equipped with valves to prevent backflow.
4. The inner lining of blood vessels, providing a smooth surface to reduce friction and regulate vessel function.
7. The thick, muscular layer of the heart responsible for contraction and pumping blood.
9. The muscular wall that separates the left and right sides of the heart to prevent mixing of oxygenated and deoxygenated blood.
10. The large vein that returns deoxygenated blood to the heart; includes the superior and inferior vena cava.
11. Relating to the arteries that supply blood to the heart muscle itself.
12. A group of specialized cells in the heart (the sinoatrial node) that regulates heartbeat by generating electrical impulses.