Describe the structure of the heart and explain the cardiac cycle

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The heart is a muscular pump that pushes blood around the body, found between the breastbone and the ribs. It is a cardiac muscle and it works involuntary. The heart has for chambers, the atria are the upper chambers, which receive blood, and the ventricles eject blood into the arteries. It has four valves separating the chambers, Tricuspid, separates the right atrium from the right ventricle, Pulmonary valve, separates the right ventricle from the pulmonary artery, Bicuspid valve separates the left atrium from the left ventricle and the Aortic valve separates the right ventricle from the aorta. The heart has three layers, epicardium, gives it a smooth texture, myocardium, responsible for the pumping action, made up of muscle fibres which connect to electrical synapses, and endocardium, inner layer that connect to large blood vessels. The left side of the heart receives oxygenated blood and the right receives deoxygenated blood. (Class notes, 2010)

Cardiac cycle
The cardiac cycle is the sequence of events including contraction and relaxation of the heart. The right side of the heart receives deoxygenated blood from the vena cava, and fills the right atrium, it then flows through the tricuspid valve and into the right ventricle. The tricuspid valve is then forced shut by ventricular pressure, ventricular systole forces the blood up through the pulmonary valve in to the artery, the ventricles are at a diastole stage which makes the pulmonary valve close to prevent back flow. Once the blood reaches the lungs it becomes oxygenated blood. It then gets transported back to the heart via the pulmonary vein and entering the left atrium, from here it goes through the bicuspid valve into the left ventricle. It then gets pumped through the Aortic valve and exits the heart under great pressure out of the aorta which then travels round the body and goes to the cells that require oxygen, the cycle then starts over again. (Class note, 2010)