The human heart constantly circulates blood throughout the body. Many people assume the heart resides entirely on the left side of the body, a belief that stems from where the strongest pulse is typically felt. Understanding the heart’s true anatomical placement clarifies this common misunderstanding.
The Heart’s True Location
The heart is not situated exclusively on the left side of the chest, but rather in the center of the thoracic cavity. This central space is known as the mediastinum, a region located between the two lungs. The heart is positioned directly behind the sternum, or breastbone, which provides a layer of protection.
While centrally located, approximately two-thirds of the heart’s volume extends toward the left side of the chest. The organ rests upon the diaphragm, the large muscle that separates the chest from the abdomen.
Understanding the Tilt and Apex
The perception that the heart is entirely on the left side is due to its specific orientation and a feature called the apex. The heart is tilted forward, downward, and toward the left. The base of the heart, where the great vessels connect, is positioned higher up, near the third costal cartilage.
The apex is the cone-shaped, inferior tip of the heart, which points toward the left side. This tip is predominantly formed by the muscular left ventricle, the chamber that generates the powerful contractions necessary to pump oxygenated blood to the entire body. Because this is the strongest part of the pump, the most noticeable sensation of the heartbeat, or apical impulse, is felt where the apex touches the chest wall. The apex is typically located just to the left of the sternum, between the junction of the fourth and fifth ribs.
Protection and Surrounding Structures
The heart is securely nestled within the chest cavity. The rib cage, which includes the sternum in the front, forms a bony shield around the heart.
The heart is also encased in a tough, double-layered sac called the pericardium. The sturdy outer layer, the fibrous pericardium, anchors the heart within the mediastinum and limits its movement. On either side, the heart is flanked by the two lungs, which fill the remainder of the thoracic space. The left lung has a slight indentation, known as the cardiac notch, which accommodates the heart’s leftward tilt.