Final answer:
The heart consists of three layers: epicardium, myocardium, and endocardium, and contains four chambers (two atria and two ventricles) partitioned by septa, with valves regulating blood flow direction. It operates in two loops: the pulmonary and systemic circuits. The heart's function is supported by its own network of coronary vessels.
Step-by-step explanation:
The Composition of the Heart
The heart is a complex muscular organ responsible for pumping blood throughout the body, and it consists of several key structures. Structurally, the heart is made up of three layers: the epicardium, the myocardium, and the endocardium. The epicardium is the outer layer, the myocardium is the thick middle layer composed of cardiac muscle cells, and the endocardium is the inner lining of the heart chambers.
Functionally, the heart comprises of two loops – the pulmonary circuit and the systemic circuit, which correspond to the dual role of receiving deoxygenated blood from the body and pumping oxygenated blood back into circulation. These functions are achieved through the heart's four chambers: two upper chambers known as atria (singular: atrium) and two lower chambers called ventricles. The right atrium and ventricle direct blood to the lungs for oxygenation, whereas the left atrium and ventricle pump oxygenated blood to the rest of the body. The septa of the heart separates these chambers, and one-way valves ensure blood flows in the correct direction.
Coronary vessels, including arteries and veins, are essential as they supply the heart muscle with oxygen-rich blood to maintain its vigorous pumping abilities. Understanding these structures is vital for grasping the heart's function in the pulmonary and systemic circuits.