Chapter 37 Prentice Hall Biology: The Circulatory and Respiratory Systems

Thick middle muscle layer of the heart; pumps blood throughout the circulatory system.

Upper chamber of the heart that receives and holds blood that is about to enter the ventricle.

Lower chamber of the heart that pumps blood out of the heart.

Pathway of circulation between the heart and lungs.

Pathway of circulation between the heart and the rest of the body except the lungs.

A flap of connective tissue between an atrium and a ventricle, a ventricle and an artery, or in a vein. It prevents the backflow of blood.

A small group of cardiac muscle cells in the right atrium that "sets the pace" for the heart as a whole. It is also called the sinoatrial node.