Talk:Intermediate - Heart Valves
--Mark Hill 13:23, 28 October 2009 (EST) This page is a little poorly organised, could you have another go and try and get a sense of progression.
--Phoebe Norville 11:39, 2 October 2009 (EST)
The AV valves begin to form between the fifth and eighth weeks of development. The valve leaflets are attached to the ventricular walls by thin fibrous chords, the chordae tendineae, which insert into small muscles attached to the ventricle wall, the papillary muscles. These structures are sculpted from the ventricular wall. The left AV valve has anterior and posterior leaflets and is termed the bicuspid or mitral valve. The right AV valve has a third, small, septal cusp and thus is called the tricuspid valve. These concepts are depicted on the left.
The aortic and pulmonary valves, termed the semilunar valves, are formed from the bulbar ridges and subendocardial valve tissue. The primordial semilunar valve consists of a mesenchymal core covered by endocardium. Excavation occurs, thinning the valve tissue thus creating its final shape (see right). These valves form the four valves of the adult heart, depicted below.