Ventricle (heart)

Ventricle
CG Heart.gif
Computer generated animation of cut section of the human heart showing both ventricles.
Details
Identifiers
Latinventriculus cordis
D006352
A12.1.00.012
7100
Anatomical terminology

A ventricle is one of two large chambers toward the bottom of the heart that collect and expel blood received from an atrium towards the peripheral beds within the body and lungs. The atrium (an adjacent/upper heart chamber that is smaller than a ventricle) primes the pump.

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.

The term "interventricular" means between the ventricles (for example the interventricular septum), while "intraventricular" means within one ventricle (for example an intraventricular block).

Structure

Heart section showing ventricles and ventricular septum

Ventricles have thicker walls than atria and generate higher blood pressures. The physiological 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 and to the mitral 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.[1]

The right ventricle is equal in size to the left ventricle[citation needed] and contains roughly 85 millilitres (3 imp fl oz; 3 US fl oz) 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 longer 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 the apex and thins towards its base at 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 (equivalent to around 11 kPa) and pushing it forward to the typical ~120mmHg pressure (around 16.3 kPa) in the aorta during each heartbeat. (The pressures stated are resting values and stated as relative to surrounding atmospheric which is the typical "0" reference pressure used in medicine.)