The cusps of the heart valves serve to seal the heart valve

Heart valve

A heart valve normally allows blood flow in only one direction through the heart. The four valves commonly represented in a mammalian heart determine the pathway of blood flow through the heart...

s when closed. There are three cusps for each valve except for the mitral valve

Mitral valve

The mitral valve is a dual-flap valve in the heart that lies between the left atrium and the left ventricle...

, which has only two (hence its alternate name, "bicuspid valve").

"Nodules" are located at the tip of the valve, to form a tighter seal.

Semilunar valves

• pulmonary valve
  Pulmonary valve
  The pulmonary valve is the semilunar valve of the heart that lies between the right ventricle and the pulmonary artery and has three cusps. Similar to the aortic valve, the pulmonary valve opens in ventricular systole, when the pressure in the right ventricle rises above the pressure in the...
  
  
  • "right cusp"
  • "left cusp"
  • "anterior cusp"

Nowhere in the literature does it describe the echocardiographic location of each pulmonary valve. According to researcher and professor Dr. Paul Michael, in the RVOT view the anterior and and right cusps can be viewed.

• aortic valve
  Aortic valve
  The aortic valve is one of the valves of the heart. It is normally tricuspid , although in 1% of the population it is found to be congenitally bicuspid . It lies between the left ventricle and the aorta....
  
  . (Note that one is absent in the condition bicuspid aortic valve
  Bicuspid aortic valve
  A bicuspid aortic valve is most commonly a congenital condition of the aortic valve where two of the aortic valvular leaflets fuse during development resulting in a valve that is bicuspid instead of the normal tricuspid configuration. Normally the only cardiac valve that is bicuspid is the mitral...
  
  .)
  • "right cusp"
  • "left cusp"
  • "posterior cusp" (or "noncoronary cusp")

Atrioventricular valves

• tricuspid valve
  Tricuspid valve
  The tricuspid valve, or right atrioventricular valve, is on the right dorsal side of the mammalian heart, between the right atrium and the right ventricle. The normal tricuspid valve usually has three leaflets and three papillary muscles. They are connected to the papillary muscles by the chordae...
  
  - right av
  • "anterior cusp" (or "infundibular cusp")
  • "posterior cusp" (or "marginal cusp")
  • "septal cusp" (or "medial cusp")

• mitral valve
  Mitral valve
  The mitral valve is a dual-flap valve in the heart that lies between the left atrium and the left ventricle...
  
  - left av
  • "anterior cusp"
  • "posterior cusp"