| A | B |
|---|
| myocardium | thick middle muscle layer of the heart |
| atrium | A chamber that receives blood returning to the vertebrate heart |
| ventricle | A muscular chamber of the heart that receives blood from an atrium and pumps blood out of the heart, either to the lungs or to the body tissues |
| pulmonary circulation | In birds and mammals, a vein that carries oxygenated blood from the lungs to the left atrium of the heart, from which blood is pumped into the left ventricle and from there to the body tissues |
| systemic circulation | A defensive response in infected plants that helps protect healthy tissue from pathogenic invasion |
| valve | flap of connective tissue between an atrium and ventricle |
| pacemaker | A specialized region of the right atrium of the mammalian heart that sets the rate of contraction; also called the sinoatrial (SA) node |
| aorta | The major artery in blood-circulating systems; the aorta sends blood to the other body tissues |
| artery | A vessel that carries blood away from the heart to organs throughout the body |
| capillary | A microscopic blood vessel that penetrates the tissues and consists of a single layer of endothelial cells that allows exchange between the blood and interstitial fluid |
| vein | A vessel that returns blood to the heart |
| atherosclerosis | condition in which fatty deposites called plaque built up on the inner walls |
| plasma | The liquid matrix of blood in which the cells are suspended |
| hemoglobin | An iron-containing protein in red blood cells that reversibly binds oxygen |
| lymphocyte | A white blood cell. The lymphocytes that complete their development in the bone marrow are called B cells, and those that mature in the thymus are called T cells |
| platelet | A small enucleated blood cell important in blood clotting; derived from large cells in the bone marrow |
| lymph | A mass of spongy tissues, separated into compartments; located throughout the lymphatic system, lymph nodes remove dead cells, debris, and foreign particles from the circulation; also are sites at which foreign antigens are displayed to immunologically active cells |
| pharynx | An area in the vertebrate throat where air and food passages cross; in flatworms, the muscular tube that protrudes from the ventral side of the worm and ends in the mouth |
| trachea | The windpipe; that portion of the respiratory tube that has C-shaped cartilagenous rings and passes from the larynx to two bronchi |
| larynx | structure in the troat containing the vocal cords |
| bronchus | One of a pair of respiratory tubes branching into either lung at the lower end of the trachea; it subdivides into progressively finer passageways, the bronchioles, culminating in the alveoli |
| alveoolus | tiny air sac at the end of a bronchiole in the lungs that provide surface area for gas exchange to occur |
| diaphragm | A sheet of muscle that forms the bottom wall of the thoracic cavity in mammals; active in ventilating the lungs |
| nicotine | stimulant drug in tobacco that increases heart rate and blood pressure |
| emphysema | disease in which the tissue of the lungs lose elasticity |
