Complex sentence: The normal diameter of the mitral annulus is 3.1 ± 0.4 cm, and the circumference is 8 to 9 cm. There is no histologic evidence of an annular structure anteriorly, where the mitral valve leaflet is contiguous with the posterior aortic root.
Split into simpler sentences: The normal diameter of the mitral annulus is, and the circumference is. Microscopically, there is no evidence of an annular structure anteriorly, where the mitral valve leaflet is contiguous with the posterior aortic root.