Then, during ventricular systole, the atrioventricular valves shut, and the semilunar valves open so that the blood leaves the heart through the great arteries, rather than re-entering the atria. The valves close if the pressure of the chamber before the valve is lower than that of the chamber the blood is flowing through, this is so that blood doesn’t go backwards due to the pressure difference.ĭuring atrial systole, the atrioventricular valves open so that blood can enter the ventricles. The valves open when the chamber before it has a higher pressure than the chamber it is leading to. Diastole: relaxation of both the atria and ventricles.This follows atrial systole after 0.1-0.2 seconds. Ventricular systole: contraction of the ventricles.Atrial systole: contraction of the atria.The cycle can then be divided into three stages: When in a relaxed state, this is called diastole. When in a contractile state, this is called systole. The left and right sides of the heart are independent of each other, however, will contract synchronously. The heart relies on its muscle to contract and relax to pump the blood around the body. The dual system of the circulatory system and the structures of the heart.

The pulmonary valve lies in the pulmonary outlet, on the right, and the aortic valve in the aortic outlet, on the left. The semilunar valves lie in the arterial outlets, connecting the ventricles to their associated great arteries. The tricuspid valve is on the right side of the heart and the mitral (or bicuspid) valve is on the left (Figure 1). The atrioventricular valves connect the atria and ventricles. The valves direct the flow of blood into the next structure and prevent backflow. There are two sets of valves, the atrioventricular and the semilunar valves, on each side of the heart. Great arteries (the pulmonary artery on the right and the aorta on the left).Great veins (the venae cavae on the right and the pulmonary vein on the left).This article will give an overview of the cardiac cycle, highlighting the physiology and clinical relevance.īlood flows through the structures of the heart in the following order: It must work in a systematic way so that the body is adequately supplied with blood. The heart is the pump of the body’s circulatory system.

Simple heart blood flow diagram