The adjoining chamber to the right atrium of the heart is the right ventricle. Blood flows from the atrium to this ventricle via the tricuspid, atrioventricular valve. The flow of blood is primarily mediated by low pressure conditions of the right ventricle during relaxation; contraction of the right atrium moves the remaining blood into the ventricle, but the volume moved during this contraction is small relative to the total volume.
The right ventricle was accessed by first probing the pulmonary valve through the pulmonary artery. Once identified, cuts were made through the anterior wall to expose the right ventricle. The inflow region of the heart has irregular, muscular elevations, known as trabeculae carneae (“fleshy beams”). The outflow portion of the ventricle is smooth, the conus arteriosis [A]. These two regions are separated by the supraventricular crest.
The tricuspid valve governs the inflow of blood to the right ventricle. Three papillary muscles project tendons onto the valve cusps like the cords of a parachute. The anterior papillary muscle [not depicted] is the largest, and arises from the anterior wall. Tendons from the anterior muscle attach to the anterior and posterior cusps. The posterior papillary muscle [B] arises from the inferior wall of the right ventricle, and tendinous cords attach to the posterior and septal cusps of the tricuspid valve. The septal papillary muscle [C] arises from the interventricular septum, and tendinous cords attach to the anterior and septal cusps. The interconnected nature of the tendons facilitates closure of the valve upon contraction of the papillary muscles. This valve prevents backflow into the right atrium during ventricular contraction.
The pulmonary valve [D] does not have tendinous chords, but instead uses semilunar (“moon”-shaped) cusps. During relaxation, blood flows back toward the heart, and semilunar cusps snap close, like an umbrella caught in the wind. This action is similar to the valves found in veins.
The heart valves are remarkable mechanical systems. These valves operate relentlessly throughout out our lives, and produce diagnostic sound patterns when not functioning properly. An echocardiogram uses sound waves to present real-time motion of the heart and valves. A 3D echocardiogram uses an array of probes to generate an even more detailed view of the heart, and is used for more precise diagnosing and treatment (click here for a video of a 3D ECHO). Nothing compares, however, to intimately placing a stethoscope upon a patient’s chest and intently listening to their heart beat.