Write the name and position of any three valves in human heart.

Answer:

1. Tricuspid valve: at the right atrio-ventricular aperture, between the right atrium and right ventricle; it has three cusps.
2. Bicuspid (mitral) valve: at the left atrio-ventricular aperture, between the left atrium and left ventricle; it has two cusps.
3. Pulmonary semilunar valve: at the base of the pulmonary trunk where it leaves the right ventricle.
4. Aortic semilunar valve: at the base of the aorta where it leaves the left ventricle.

These valves allow blood to flow in one direction only and prevent its backflow. (Other valves: Eustachian valve at the opening of the inferior vena cava and Thebesian valve at the opening of the coronary sinus into the right atrium.)