Pulmonary and systemic circulation differ significantly in terms of the heart's structure and function. Pulmonary circulation involves the right side of the heart, where the right ventricle pumps deoxygenated blood to the lungs through the pulmonary artery. This circuit is shorter and involves lower pressure, hence the right ventricle has a thinner muscular wall. Systemic circulation, on the other hand, involves the left side of the heart. The left ventricle, with its thick muscular wall, pumps oxygenated blood to the entire body through the aorta. This requires higher pressure to overcome the resistance of the extensive body's blood vessels. The structural differences between the two sides of the heart reflect their distinct roles: the right side deals with low-pressure pulmonary circulation, while the left side manages the high-pressure demands of systemic circulation.

Intercalated discs are specialized structures in cardiac muscle tissue that play a crucial role in the heart's function. They contain gap junctions and desmosomes. Gap junctions facilitate electrical connectivity, allowing cardiac muscle cells to contract in a coordinated and synchronized manner. This synchronization is essential for the effective pumping of blood; it ensures that the heart chambers contract in unison, optimizing blood flow. Desmosomes, on the other hand, provide structural stability by anchoring cardiac cells together, allowing the heart to withstand the mechanical stress of continuous contractions. Without intercalated discs, the heart's muscle cells would not function cohesively, significantly impairing the heart's ability to pump blood efficiently.

Heart valves prevent the backflow of blood by opening and closing in response to pressure changes in the heart's chambers. Each valve consists of flaps (cusps or leaflets) that operate in a one-way mechanism. When the heart contracts, pressure builds up, forcing the valves open and allowing blood to flow through. After the blood has passed, the pressure decreases, causing the valves to close. This closing action prevents blood from flowing backward. For example, the mitral and tricuspid valves close when the ventricles contract, preventing blood from flowing back into the atria. Similarly, the aortic and pulmonary valves close when the ventricles relax, stopping blood from returning to the ventricles. Any dysfunction in these valves can lead to inefficient blood flow and various heart conditions.

Lifestyle factors significantly impact the health of the coronary arteries. Unhealthy lifestyle choices, such as a diet high in saturated fats, lack of physical activity, smoking, and excessive alcohol consumption, can lead to the development of coronary artery disease (CAD). These factors contribute to the buildup of plaque—a combination of fat, cholesterol, calcium, and other substances—in the coronary arteries. This condition, known as atherosclerosis, narrows the arteries, reducing blood flow to the heart muscle. Reduced blood flow can cause chest pain (angina), shortness of breath, or other symptoms. In severe cases, complete blockage can lead to a heart attack. Conversely, healthy lifestyle choices like regular exercise, a balanced diet, and avoiding smoking can significantly reduce the risk of CAD, maintaining the health and functionality of the coronary arteries.

The left ventricle is more muscular than the right ventricle due to its role in systemic circulation. It is responsible for pumping oxygenated blood to all parts of the body, which requires generating a high pressure to overcome the resistance of the systemic blood vessels. This high-pressure pump needs a stronger muscular wall to efficiently push the blood throughout the extensive circulatory network reaching the entire body. In contrast, the right ventricle pumps deoxygenated blood to the lungs, which is a shorter distance and involves less resistance. Therefore, it requires less force, accounting for its thinner muscular wall. The structural differences between the two ventricles highlight the heart's adaptation to varying circulatory demands, ensuring that each section of the heart is suitably equipped for its specific function.