The right atrioventricular valvular apparatus in the chick heart

The purpose of this study was to describe the detailed anatomy and histology of the right atrioventricular valve apparatus in the chicken. Newborn and adult chicken hearts were studied by anatomic description, light and scanning electron microscopy, and histologic (Masson's trichrome stain) and histochemical (Sirius Red stain) techniques. Our findings indicate the presence of an incomplete fibrous annulus, a great mural leaflet, and multiple microleaflets in the right atrioventricular apparatus of the chicken heart. The great mural leaflet, essentially muscular in structure, extended from the anterior and posterior juxtaseptal commissures and was subdivided into an anterior and a posterolateral region by the attachment of the anterolateral papillary muscle. The posterolateral region presented an intermediate cleft, subdividing this region into an anterior and a posterior portion. Multiple microleaflets, which adhered to the upper right side of the ventricular septum adjacent to the right atrioventricular orifice, inserted directly into the ventricular septum via short chordae tendineae, without papillary muscles. The microleaflets were composed of smooth subendocardial connective tissue, with varying amounts of type I, II and III collagen. In addition, we observed a central fibrous body, leading to fibrous continuity between the mitral and aortic valves and the mitral and right atrioventricular valves. An atrioventricular septum was also present.(ABSTRACT TRUNCATED AT 250 WORDS)