| A | B |
|---|
| cardiovascular system | The body system that consists of the heart, blood vessels, and blood, and that carries needed substances to cells and carries waste products away from cells |
| heart | A hollow, muscular organ that pumps blood throughout the body |
| atrium | Each of the two upper chambers of the heart that receives blood that comes into the heart. |
| ventricle | A lower chamber of the heart that pumps blood out to the lungs and body |
| valve | A flap of tissue in the heart or a vein that prevents blood from flowing backward. |
| pacemaker | A group of cells located in the right atrium that sends out signals that make the heart muscle contract and that regulates heartbeat rate |
| artery | A blood vessel that carries blood away from the heart |
| capillary | A tiny blood vessel where substances are exchanged between the blood and the body cells |
| vein | A blood vessel that carries blood back to the heart |
| aorta | A blood vessel that carries blood back to the heart |
| coronary artery | An artery that supplies blood to the heart itself. |
| diffusion | The process by which molecules move from an area in which they are highly concentrated to an area in which they are less concentrated. |
| blood pressure | The pressure that is exerted by the blood against the walls of blood vessels |
| respiration | the process by which cells break down simple food molecules to release the energy they contain |
| cillia | the hairlike projections on the outside of cells that move in a wavelike manner |
| pharynx | the throat |
| trachea | the windpipe; a passage through which air oves in the respiratory system |
| bronchi | the passages that direct air into the lungs |
| lungs | an organ found in air-breathing bertebrates that exchanges oxygen and carbon dioxide with the blood |
| alveoli | timy sacs of lung tissue specialized for the movement of gases between air and blood |
| diaphragn | a large muscle located at the bottom of a mammal's rib cage that functions in breathing |
| larynx | the voice box |
| vocal cords | folds of connective tissue that stretch across the opening of the larynx and produce a person's voice |
