The heart valves play a crucial role in ensuring unidirectional blood flow through the heart. They function like one-way gates, opening and closing in response to pressure changes in the heart's chambers. When the pressure in a chamber exceeds that in the adjoining pathway, the valves open, allowing blood to flow through. Conversely, when the pressure behind the valve increases, the valve closes, preventing backflow. This mechanism is critical in maintaining efficient circulation. The atrioventricular valves (tricuspid and mitral) prevent backflow into the atria during ventricular contraction, while the semilunar valves (pulmonary and aortic) prevent backflow into the ventricles after blood has been ejected into the arteries.

The left ventricle has a more muscular wall compared to the right ventricle due to the differing demands placed upon each chamber. The primary role of the left ventricle is to pump oxygenated blood under high pressure to the entire body (systemic circulation), which requires significant force. Consequently, its muscular wall is thicker to generate the necessary high pressure. In contrast, the right ventricle pumps deoxygenated blood to the lungs (pulmonary circulation) under a lower pressure, as the lungs are closer and the pulmonary circuit is a shorter, lower resistance pathway. Thus, the right ventricle requires less muscular force and has a thinner wall.

The chordae tendineae and papillary muscles function together to prevent the inversion of the atrioventricular (AV) valves (tricuspid and mitral valves) during ventricular contraction. The chordae tendineae are strong, fibrous strings that attach the cusps of the AV valves to the papillary muscles, which are small muscular projections from the inner walls of the ventricles. During ventricular systole (contraction), the pressure within the ventricles rises sharply, which could force the valve cusps back into the atria. However, the contraction of papillary muscles tenses the chordae tendineae, holding the valve cusps in place and ensuring they seal tightly. This arrangement effectively prevents the backflow of blood into the atria during ventricular contraction.

The heart's own blood supply, primarily through the coronary arteries, is critical for its function. Despite being filled with blood, the heart muscle (myocardium) cannot extract oxygen and nutrients directly from the blood within its chambers. Instead, it relies on the coronary arteries to deliver oxygenated blood and nutrients directly to the myocardial tissue. This is essential because the heart muscle is constantly active, contracting rhythmically to pump blood throughout the body. Without this dedicated blood supply, the myocardium would be unable to sustain its continuous, high-energy demands, leading to impaired heart function and potentially life-threatening conditions like myocardial infarction (heart attack) due to ischemia (lack of oxygen).

The pericardium plays a crucial role in the heart's function by providing physical protection and stabilising its position within the thorax. It consists of two layers: the fibrous pericardium and the serous pericardium. The fibrous pericardium is a tough, inelastic sac that encloses the heart and anchors it to the surrounding structures, like the diaphragm and the sternum, preventing excessive movement. The serous pericardium, on the other hand, forms a double layer around the heart with a small space in between filled with pericardial fluid. This fluid acts as a lubricant, reducing friction between the heart's surface and surrounding tissues as the heart beats, facilitating smooth cardiac movements.