Heart valve chambers are lined with endocardium. Heart valves separate the atria from the ventricles, or the ventricles from a blood vessel. Heart valves are situated around the fibrous rings of the cardiac skeleton. The valves incorporate leaflets or cusps, which are pushed open to allow blood flow and which then close together to seal and prevent backflow. The mitral valve has two cusps, whereas the others have three. There are nodules at the tips of the cusps that make the seal tighter. The pulmonary valve has left, right, and anterior cusps. The aortic valve has left, right, and posterior cusps. The
How Many More Times How Many More Times "How Many More Times" is the ninth and final track on English rock band Led Zeppelin's 1969 debut album "Led Zeppelin". The song is credited in the album liner to Jimmy Page, John Paul Jones, and John Bonham, but Robert Plant was later added to the ASCAP credits. At eight and a half minutes, "How Many More Times" is the longest song on the album. It is one of three Led Zeppelin songs on which Page used bowed guitar. In an interview he gave to "Guitar World" magazine in 1993, Page stated that the song "was