The sternum, often called the breastbone, is a flat bone positioned centrally in the chest. It serves as a protective shield for underlying organs and acts as a connecting point for other skeletal structures. This bone forms an integral part of the rib cage. Its location and composition make it a significant anatomical feature.
Locating the Sternum
The sternum lies in the center of your chest. You can begin by gently placing your fingers at the base of your neck, just above where your collarbones meet. This slight depression is the jugular notch, the very top of your sternum. Moving your fingers downward from this notch, you will feel the flat, firm bone extending vertically along the midline of your chest.
The sternum continues down between your ribs, which attach to it. You can trace its length until you reach the soft tissue of your upper abdomen. The sternum is easily palpable beneath the skin, making it a reliable landmark.
Structure of the Sternum
The sternum is a long, flat bone, measuring about 6 inches in length in adults. It is composed of three parts that fuse together as a person matures. The uppermost section is the manubrium, a broad, handle-like portion that articulates with the clavicles, or collarbones, and the first pair of ribs. Below the manubrium lies the body of the sternum, which is the longest and flattest part. The body provides attachment points for the costal cartilages of the second through seventh ribs.
At the very bottom of the sternum is the xiphoid process, a small, often pointed projection. This lowest part is primarily cartilaginous in younger individuals and gradually hardens into bone with age. The connection between the manubrium and the body forms a slight angle, known as the sternal angle, which helps identify the second rib.
Function of the Sternum
The sternum protects organs within the chest cavity. Along with the ribs, it forms the anterior portion of the rib cage, creating a barrier for the heart, lungs, and major blood vessels. This bony shield helps absorb impacts and prevent damage to these internal structures.
Beyond protection, the sternum also serves as an anchor point for the rib cage. It connects to the ribs via cartilage, contributing to the stability and integrity of the thoracic cavity. This arrangement allows for expansion and contraction of the chest during breathing. The sternum additionally provides attachment sites for various muscles of the chest and upper abdomen, including portions of the pectoralis major and the diaphragm.