In the heart, a ventricle is one of two large chambers that collect and expel blood received from an atrium towards the peripheral beds within the body and lungs. The atrium primes the pump. Interventricular means between the ventricles, while intraventricular means within one ventricle. In a four-chambered heart, such as that in humans, there are two ventricles that operate in a double circulatory system: the right ventricle pumps blood into the pulmonary circulation to the lungs, and the left ventricle pumps blood into the systemic circulation through the aorta. Structure Ventricles have thicker walls than atria and generate higher blood pressures.
The physiologic load on the ventricles requiring pumping of blood throughout the body and lungs is much greater than the pressure generated by the atria to fill the ventricles. Further, the left ventricle has thicker walls than the right because it needs to pump blood to most of the body while the right ventricle fills only the lungs. On the inner walls of the ventricles are irregular muscular columns called trabeculae carneae which cover all of the inner ventricular surfaces except that of the conus arteriosus, in the right ventricle. There are three types of these muscles. The third type, the papillary muscles give origin at their apices to the chordae tendinae which attach to the cusps of the tricuspid valve. The mass of the left ventricle, as estimated by magnetic resonance imaging, averages 143 g ± 38.4 g, with a range of 87––224 g. The right ventricle is equal in size to that of the left ventricle, and contains roughly 85 millilitres in the adult.
Its upper front surface is circled and convex, and forms much of the sternocostal surface of the heart. Its under surface is flattened, forming part of the diaphragmatic surface of the heart that rests upon the diaphragm. Its posterior wall is formed by the ventricular septum, which bulges into the right ventricle, so that a transverse section of the cavity presents a semilunar outline. Its upper and left angle forms a conical pouch, the conus arteriosus, from which the pulmonary artery arises. A tendinous band, called the tendon of the conus arteriosus, extends upward from the right atrioventricular fibrous ring and connects the posterior surface of the conus arteriosus to the aorta.
Shape The left ventricle is shorter and more conical in shape than the right, and on transverse section its concavity presents an oval or nearly circular outline. It forms a small part of the sternocostal surface and a considerable part of the diaphragmatic surface of the heart; it also forms the apex of the heart. The left ventricle is thicker and more muscular than the right ventricle because it pumps blood at a higher pressure.
The right ventricle is triangular in shape and extends from the tricuspid valve in the right atrium to near the apex of the heart. Its wall is thickest at its base and thins towards the atrium. Development By early maturity, the walls of the left ventricle have thickened from three to six times greater than that of the right ventricle. This reflects the typical five times greater pressure workload this chamber performs while accepting blood returning from the pulmonary veins at ~80mmHg pressure and pushing it forward to the typical ~120mmHg pressure in the aorta during each heartbeat. Function During systole, the ventricles contract, pumping blood through the body.
During diastole, the ventricles relax and fill with blood again. The left ventricle receives oxygenated blood from the left atrium via the mitral valve and pumps it through the aorta via the aortic valve, into the systemic circulation. The left ventricular muscle must relax and contract quickly, and be able to increase or lower its pumping capacity under the control of the nervous system. In the diastolic phase, it has to relax very quickly after each contraction so as to quickly fill with the oxygenated blood flowing from the pulmonary veins. Likewise in the systolic phase, the left ventricle must contract rapidly and forcibly to pump this blood into the aorta, overcoming the much higher aortic pressure. The extra pressure exerted is also needed to stretch the aorta and other arteries to accommodate the increase in blood volume. The right ventricle receives deoxygenated blood from the right atrium via the tricuspid valve and pumps it into the pulmonary artery via the pulmonary valve, into the pulmonary circulation.
Pumping volume The typical healthy adult heart pumping volume is ~5 liters/min, resting. Maximum capacity pumping volume extends from ~25 liters/min for non-athletes to as high as ~45 liters/min for Olympic level athletes. Volumes In cardiology, the performance of the ventricles are measured with several volumetric parameters, including end-diastolic volume, end-systolic volume, stroke volumeand ejection fraction. Dimensions The heart and its performance are also commonly measured in terms of dimensions, which in this case means one-dimensional distances, usually measured in millimeters.
This is not as informative as volumes, but may be much easier to estimate with e.g. M-Mode echocardiography or with sonomicrometry. Optimally, it is specified with which plane the distance is measured in, e.g. The dimension of the longitudinal plane. Fractional shortening is the fraction of any diastolic dimension that is lost in systole. When referring to endocardial luminal distances, it is EDD minus ESD divided by EDD. Normal values may differ somewhat dependent on which anatomical plane is used to measure the distances.
Normal range is 25-45%, Mild is 20-25%, Moderate is 15-20%, and Severe is <15%. Cardiology Diagnostic Tests Midwall fractional shortening may also be used to measure diastolic/systolic changes for inter-ventricular septal dimensions and posterior wall dimensions. However, both endocardial and midwall fractional shortening are dependent on myocardial wall thickness, and thereby dependent on long-axis function.
By comparison, a measure of short-axis function termed epicardial volume change is independent of myocardial wall thickness and represents isolated short-axis function. Clinical significance Cardiac dysrhythmia or arrhythmia is an irregular heartbeat that can occur in the ventricles or atria. Normally the heartbeat is initiated in the SA node of the atrium but initiation can also occur in the Purkinje fibres of the ventricles giving rise to premature ventricular contractions, also called ventricular extra beats. When these beats become grouped the condition is known as ventricular tachycardia. Another form of arrhythmia is that of the ventricular escape beat.
This can happen as a compensatory mechanism when there is a problem in the conduction system from the SA node. The most severe form of arrhythmia is ventricular fibrillation which is the most common cause of cardiac arrest and subsequent sudden death. Ventricular septal defect Atrioventricular septal defect External links Photo of dissection at uc.edu Left Ventricle - Cell Centered Database Anatomy photo:20:05-0102 at the SUNY Downstate Medical Center See also Atrium References.
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