Here is a comprehensive summary of the article on the human heart:

The heart is a muscular organ that pumps blood through the circulatory system, delivering essential oxygen and nutrients to tissues while removing metabolic waste like carbon dioxide. In humans, this four-chambered organ (two atria and two ventricles) uses valves to ensure one-way blood flow, with its rhythm controlled by the electrical impulses of the sinoatrial node. Blood follows a precise pathway: deoxygenated blood enters the right heart, travels to the lungs for oxygen, returns to the left heart, and is then pumped through the aorta to the body. Roughly the size of a closed fist and located in the chest's mediastinum, it beats at a resting rate of about 72 beats per minute. However, cardiovascular diseases remain the leading cause of death globally, responsible for an estimated 19.8 million deaths in 2022 (about 32% of all deaths), with major risk factors including smoking, high blood pressure, and poor lifestyle habits.