Читать книгу Understanding Anatomy and Physiology in Nursing - John Knight - Страница 88

The ventricles are the two inferior (lower) chambers of the heart; these are much thicker than the atria, containing the bulk of the cardiac muscle mass of the myocardium. The ventricles function as the primary pumping chambers of the heart and are responsible for pumping around 7,200 litres of blood around the body per day. The left and right ventricles are separated by a thick muscular interventricular septum which effectively separates the heart into two distinct pumping mechanisms. Internally within the heart there are four valves which ensure that blood flows in the correct direction.

The two upper valves are semi-lunar valves called the pulmonary and aortic valves which close to prevent blood flowing back into the heart following contraction of the ventricles. The lower two valves are termed atrioventricular (AV) valves since they separate the atria from the ventricles. The AV valve on the right side consists of three flaps (cusps) of tissue and is therefore called the tricuspid, while the AV valve on the left consists of two cusps and is termed the bicuspid or mitral valve. The role of the AV valves is to close and prevent blood flowing back into the atria during ventricular contraction.

Figure 3.3 Internal structure of the heart showing direction of blood flow