What are cardiac valves?

• A. One-way tissue flaps that open and close in response to pressure changes within the heart chambers
• B. Muscular ridges that strengthen chamber walls
• C. Nerves that regulate heart rate
• D. Blood vessels supplying the heart muscle

Answer: (A)

Cardiac valves are one-way tissue flaps that open and close in response to pressure changes within the heart chambers. They ensure blood flows in one direction and prevent backflow as the heart beats. There are four valves: two between the atria and ventricles (the mitral and tricuspid valves) and two at the outlets to the great vessels (the aortic and pulmonary valves). Each valve has leaflets or cusps that seal when the upstream pressure drops or the downstream pressure rises, preventing regurgitation. The valve function is supported by structures like the chordae tendineae and papillary muscles, which help prevent the leaflets from prolapsing during contraction. Valve opening and closing occur passively based on pressure gradients between adjacent chambers and vessels. They are not muscular ridges, nerves, or blood vessels supplying the heart muscle.