The left atrioventricular valve or mitral valve (bicuspid valve ; valvula bicuspidalis [metralis]) is attached to the circumference of the left atrioventricular orifice in the same way that the tricuspid valve is on the opposite side.
It consists of two triangular cusps, formed by duplicatures of the lining membrane, strengthened by fibrous tissue, and containing a few muscular fibers.
The cusps are of unequal size, and are larger, thicker, and stronger than those of the tricuspid valve.
The larger cusp is placed in front and to the right between the atrioventricular and aortic orifices, and is known as the anterior or aortic cusp; the smaller or posterior cusp is placed behind and to the left of the opening. Two smaller cusps (Commissural cusps) are usually found at the angles of junction of the larger. The cusps of the bicuspid valve are furnished with chordæ tendineæ, which are attached in a manner similar to those on the right side; they are, however, thicker, stronger, and less numerous.