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Editor-In-Chief: C. Michael Gibson, M.S., M.D. ; Assistant Editor(s)-in-Chief: Rim Halaby
- In the heart, a ventricle is a heart chamber which collects blood from an atrium (another heart chamber that is smaller than a ventricle) and pumps it out of the heart.
- In a four-chambered heart, such as that in humans, there are two ventricles:
- The right ventricle pumps blood into the pulmonary circulation for the lungs.
- The left ventricle pumps blood into the systemic circulation for the rest of the body. (See Double circulatory system for details.)
- Ventricles have thicker walls than the atria, and thus can withstand higher blood pressure.
- Comparing the left and right ventricle, the left ventricle has thicker walls because it needs to pump blood to the whole body.
- The right ventricle forms almost the entire inferior border of the heart, the largest part of the anterior surface of the heart, and also contributes to the diaphragmatic surface.
- The interior of the right ventricle has irregular muscle elevations called trabeculae carneae.
- The flow of blood in the right ventricle:
- The inflow of blood into the right ventricle enters first posteriorly.
- The outflow of blood leaves superiorly and to the left at the level of the pulmonary trunk.
- Therefore, blood takes a U-shaped path through the right ventricle in a total tract length of 2 cm.
- The inflow part receives deoxygenated blood from the right atrium through the right atrioventricular or tricuspid, orifice via the tricuspid valve.
- The orifice is a located retro-sternally between fourth and fifth intercostal spaces.
- It is characterized by a unique fibrous ring that resists dilation due to pressure variations.
- The tricuspid valve contains 3 cusps: anterior, posterior, and septal.
- The valve cusps play an important role in preventing blood regurgitation from the right ventricle to the right atrium during ventricular contraction.
- Hence when blood is forced through the right atrio-ventricular orifice, the tricuspid valve cusps are pushed aside.
- All tricuspid valve cusps are attached on their free edges and ventricular surfaces via delicate tendons called tendinous chords (L. chordae tendineae) on their free edges; with each chord attaching simultaneously 2 adjacent valve cusps.
- The tendinous chords function in preventing valvular prolapse when ventricular pressure rises due to ventricular contraction.
- Papillary muscles are three projections whose apices give rise to tendinous chords.
- Their bases are attached to the wall of the right ventricle.
- With respect to the right ventricle, they are located anteriorly, posteriorly, and septally and hence named accordingly.
- The anterior papillary muscle is the largest, while the septal is the smallest and mayb be multiple.
- Significantly, papillary muscles contract before contraction of the right ventricular in order to tighten the tendinous chords. As such, the tricuspid valve closes by drawing the cusps together before ventricular contraction and blood is prevented from regurgitation to the right atrium.
- Interventricular septum is a strong oblique wall between the right and left ventricles. It is composed of two parts:
- Membranous: thin, superoposterior part and continuous with the fibrous skeleton of the heart.
- Muscular: thick bulge into the cavity of the right ventricle. The prominent bulging is due to the overwhelming pressure in the left ventricle with respect to its counterpart in the right side.
Septomarginal Trabecula (Moderator Band)
- The septomarginal trabecula is a curved muscular bundle running from the inferior part of the inter-ventricular septum to the base of the anterior papillary muscle.
- It carries part of the right bundle branches of the AV bundle, necessary for electrical conduction, to the anterior papillary muscle of the right ventricle.
- It is believed that via this conduction route that the anterior papillary muscle achieves its coordinated contraction.
- The pulmonary valve is located at the apex of the conus arteriosus (infundibulum), a smooth-walled, cone-shaped portion of the right ventricle inferior to the opening of the pulmonary trunk (pulmonary artery).
- It is at the level of the left third costal cartilage.
- The pulmonary valve contains three semilunar cusps: anterior, right, and left.
- Each semilunar valve is concave when viewed superiorly and has three structures: one fibrous nodule and two lunules.
- The nodule and the lunules help sealing the valve cusps a prevent backflow of blood during diastole.
Pulmonary Sinus and Pulmonary Trunk
- Pulmonary sinuses are the spaces at the origin of the pulmonary trunk between the dilated wall of the vessel and each cusp of the pulmonary valve.
- Blood in the pulmonary sinuses prevents sticking of the cusps to the walls of the pulmonary trunk and consequential failure to close.
- The left ventricle is characterized by its thick muscular wall that covered by more numerous trabeculae carneae than in the right ventricle.
- Muscularization of the left ventricle grants it a sufficient work performance to pump blood appropriately to the systemic circulation and to feed all vascular beds.
Mitral (Bicuspid) Valve
- The left ventricle contains the mitral valve at the level of the AV orifice. The mitral valve is located substernally at the fourth sternocostal junction.
- It is composed of 2 cusps: anterior and posterior.
- The mitral valve is attached to the left ventricle by two papillary muscles: anterior and posterior, each giving rise to tendinous cords to both cusps simultaneously.
- Although functionally similar to the papillary muscles in the right ventricle, the anterior and posterior papillary muscles in the left ventricle are anatomically larger.
- The aortic vestibule is a supero-anterior component of the left ventricle that delineates the left ventricle’s outflow tract.
- In contrast to the muscular component of the left ventricle, the aortic vestibule is fibrous smooth-walled structure that is non-muscular.
- At the end of the aortic vestibule in its right postero-superior part lies an oblique aortic valve and the aortic orifice, the beginning of the ascending aorta.
Aortic (Semilunar) Valve
- The left ventricle and the aortic orifice are separated by the aortic valve.
- It is located substernally near the left sterno-costal junction.
- Similar to other valves in the heart, the aortic valve is surrounded by a fibrous ring that allows the three valve cusps to attach to.
- The three aortic valve semilunar cusps are named according to their position: right, posterior, and left.
- Aortic sinuses are bulges at the base of the ascending aorta between its wall and the aortic valve cusps that give rise to the coronary arteries, the arteries that supply the myocardium with oxygen and nutritional demands.
- The right aortic sinus is associated to the right coronary artery; the left aortic sinus is associated to the left coronary artery, while the posterior aortic sinus is not associated with any coronary artery. Thus it is called the non-coronary sinus.
- Kishore, K. (2003). The Heart of Structural Development: The Functional Basis of the Location and Morphology of the Human Vascular Pump. J Postgrad Med, 49:282-4.
- Moore, K. L., Agur, A. M., & Dalley, A. F. (2011). Essential Clinical Anatomy - Fourth Edition. Lippincott Williams & Wilkins.
- Tank, P. W. (2009). Grant's Dissector - Fourteenth Edition. Lippincott Williams & Wilkins.
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