Glossary

artery
A vessel that carries blood away from the heart to organs throughout the body.

arteriosclerosis
A cardiovascular disease caused by the formation of hard plaques within the arteries.

atrioventricular valve
A valve in the heart between each atrium and ventricle that prevents a backflow when the ventricles contract.

atrium (AY-tree-um) (plural, atria)
A chamber that receives blood returning to the vertebrate heart.

blood pressure
The hydrostatic force that blood exerts against the wall of a vessel.

cardiac muscle (KAR-dee-ak)
A type of muscle that forms the contractile wall of the heart; its cells are joined by intercalated discs that relay each heartbeat.

cardiac output
The volume of blood pumped per minute by the left ventricle of the heart.

cardiovascular system (KAR-dee-oh-VAS-kyuh-ler)
A closed circulatory system with a heart and branching network of arteries, capilleries, and veins.

capillary (KAP-ill-air-ee)
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.

diastole (dy-ASS-toh-lee)
The stage of the heart cycle in which the heart muscle is relaxed, allowing the chambers to fill with blood.

double circulation
A circulation scheme with separate pulmonary and systemic circuits, which ensures vigorous blood flow to all organs.

pacemaker
A specialized region of the right atrium of the mammalian heart that sets the rate of contraction; also called the sinoatrial (SA) node.

SA (sinoatrial) node
The pacemaker of the heart, located in the wall of the right atrium. At the base of the wall separating the two atria is another patch of nodal tissue called the atrioventricular node (AV).

semilunar valve
A valve located at the two exits of the heart, where the aorta leaves the left ventricle and the pulmonary artery leaves the right ventricle.

systole (SIS-toh-lee)
The stage of the heart cycle in which the heart muscle contracts and the chambers pump blood.

vein
A vessel that returns blood to the heart.