Heart

The heart is a muscular organ located in the thoracic cavity, between the lungs, and is roughly the size of a closed fist. Its primary function is to pump blood throughout the body, acting as the central component of the cardiovascular system. The human heart has four chambers: two upper atria and two lower ventricles. The right side of the heart receives deoxygenated blood from the body and pumps it to the lungs for oxygenation. Conversely, the left side receives oxygen-rich blood from the lungs and distributes it to the rest of the body. This process is vital for providing oxygen and nutrients to tissues and removing carbon dioxide and other waste products.

The heart operates through a precise sequence of electrical and mechanical events. The sinoatrial (SA) node, located in the right atrium, generates electrical impulses that initiate each heartbeat. This natural pacemaker causes the atria to contract, pushing blood into the ventricles. The impulses then reach the atrioventricular (AV) node and travel along specialized pathways to the ventricles, triggering their contraction and forcing blood out of the heart. The cardiac cycle comprises these coordinated contractions (systole) and relaxations (diastole), maintaining a constant and rhythmic flow of blood, essential for life.