Anatomy and Function of the Heart

The heart is a muscular organ that functions as the primary pump for the cardiovascular system, which is responsible for circulating blood throughout the body. The heart is located obliquely in the mediastinum, weighing between 250-350 grams[1,5]. It is composed of four chambers: the left atrium, right atrium, left ventricle, and right ventricle. The left side of the heart supplies blood to the systemic circulation, while the right side supplies blood to the pulmonary circulation. The chambers are separated by atrioventricular valves (AV valves), with the mitral (bicuspid) valve separating the left atrium and left ventricle, and the tricuspid valve separating the right atrium and right ventricle.

The heart has unique properties that enable it to function as a pump, including branching striated cardiac muscle cells with myofibrils, intercalated discs containing desmosomes and gap junctions, and an abundance of mitochondria, which depend on aerobic respiration to generate adenosine tri-phosphate (ATP). The heart's contractility is regulated by the autonomic nervous system, with the sympathetic nervous system stimulating heart rate and contractility, and the parasympathetic nervous system slowing heart rate and contractility.

The cardiovascular system consists of a continuum of blood vessels, including arteries, veins, and capillaries, that traverse the human body. Arteries are blood vessels that transport blood away from the heart, and veins transport blood back to the heart. Capillaries are the smallest blood vessels, where exchange of nutrients, gases, wastes, and immune cells occurs between blood and tissue cells. The heart's pumping action maintains a balance between cardiac output (CO) and venous return, with CO being the amount of blood pumped out by each ventricle in one minute.

The systemic circulation originates in the left side of the heart and delivers oxygen-laden blood to all organs of the human body through the aortic semilunar valve. The pulmonary circulation is on the right side of the heart and serves the function of gas exchange, with oxygen-poor systemic blood reaching the right atrium via the superior vena cava, inferior vena cava, and coronary sinus. The cardiac cycle, which refers to events that occur during one heartbeat, is split into ventricular systole (contraction) and ventricular diastole (relaxation).

The coronary circulation is the circulation to the heart organ itself, with the right and left coronary arteries branching from the ascending aorta and supplying the heart muscle tissue. Venous blood collected by the cardiac veins (great, middle, small, and anterior) flows into the coronary sinus, ensuring delivery of oxygen-rich blood to the myocardial tissue during the heart relaxation phase.

In summary, the heart is a complex organ that plays a crucial role in the cardiovascular system by pumping blood throughout the body. Its unique properties, including specialized cardiac muscle cells and an intricate network of blood vessels, enable it to maintain homeostasis and support the basic functions of human cells and organs.