Final answer:
The valve cusps, commissures, and valve annulus are structures integral to heart valve function, supporting directional blood flow and preventing backflow. Cusps are part of the valves that open and close, commissures are the joining areas of cusps, and the annulus is the anchoring ring for the cusps.
Step-by-step explanation:
The valve cusps, commissures, and valve annulus are structures related to the operation of heart valves, ensuring unidirectional blood flow. Valve cusps are flap-like structures, either bicuspid or tricuspid, that open and close to regulate blood flow between the chambers of the heart.
The commissures are points where the cusps come together, and are vital to the proper function and closure of the valves during the cardiac cycle. The valve annulus is the fibrous ring that serves as the attachment site for the valve cusps and maintains the shape and structural integrity of the valve.
Atrioventricular (AV) valves, such as the tricuspid and mitral valves, have chordae tendineae and papillary muscles to anchor their cusps, preventing backflow into the atria. However, the semilunar valves, such as the aortic and pulmonary valves, lack these structures but still efficiently prevent backflow thanks to their unique half-moon shape.