Cardiac Anatomy and Physiology

Understanding what makes up the heart better prepares the student nurse to understanding cardiac disorders.

Heart is a muscular pump that drives the blood through the circulatory system; it is located in the chest wall in the region of the mediastinum. The heart weighs an between 7 and 15 ounces and is the approximate size of the human fist. The heart is made of layers and chambers, the hearts layers are the endocardium which is the thin smooth layer that lines the interior heart it also lines the valves and large vessels, the mayocardium level is the thickest and longest layer and forms the heart wall, the epicardium is thin and the outermost layer and lastly the pericardium is the serous lining of the pericardial sac that is separated from the epicardium by a very thin layer of fluid.

The heart is made up of chambers the right atrium which receives venous blood while the right ventricle pumps the venous blood to the lungs, the left atrium receives the oxygenated blood from the lungs and the left ventricle pumps the oxygenated blood to the aorta and then through the rest of the body. The tissue that divides the right and left side of the heart is called the septum. For blood to flow correctly and not back flow there are 4 valves in place to aid in the correct flow. The 2 AV valves are located between the atria and the ventricles and the 2 semilunar valves are located at the point where the blood exits the ventricles.

AV valves are made up of the tricuspid valve which has 3 cusps and is located between the right atrium and the right ventricle. The mitral valve has 2 bicuspids and is located between the left atrium and the left ventricle. The semilunar valves are made up of the pulmonary valve which is located between the right ventricle and pulmonary artery and the aortic valve is located between the left ventricle and the aorta.

The circulation of blood through the heart follows a path, this path is the: superior and inferior vena cava -->tricuspid valve -->right ventricle -->pulmonary valve -->pulmonary artery -->lungs -->pulmonary vein --> left atrium --> mitral valve --> left ventricle --> aortic valve --> aortic arch àaorta --> the body.

Cardiac output is the amount of blood that is pumped by each ventricle for a time frame of 1 minute, the stroke volume is the blood that is ejected from the ventricles with each beat and the heart rate is the number of times the heart beats per minute.

Sources:
Mosby (2005) Foundations and Adult Health Nursing (5th ed.) Missouri: Christensen & Kockrow.
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