The sternum, often called the breastbone, is a flat bone situated in the central part of your chest. It connects to other parts of your skeletal system and forms the front of the rib cage, which encloses significant internal structures.
Precise Location
The sternum is positioned in the midline of the chest, on the anterior, or front, aspect of the torso. You can easily feel this bone by placing your fingers at the center of your upper chest. It extends vertically from the base of the neck region down towards the upper abdomen, lying between the lungs.
At its superior, or upper, end, the sternum connects with the clavicles, commonly known as collarbones, which run horizontally across the top of the chest. Inferiorly, it extends towards the area above the diaphragm. Its central position makes it a component of the thoracic cage, forming its anterior boundary.
Anatomical Components
The sternum is composed of three distinct sections that fuse together, often described as resembling an upside-down sword or a necktie. The uppermost, broadest part is the manubrium, which translates to “handle” in Latin. This section is roughly trapezoidal and articulates with the clavicles and the first pair of ribs, along with part of the second pair.
Below the manubrium lies the body of the sternum, also known as the gladiolus or “sword blade,” which is the longest and flattest section. The manubrium and the body meet at a slight angle, forming a palpable ridge known as the sternal angle. This angle serves as an anatomical landmark, as it is where the second ribs attach and can be used to count ribs. The body of the sternum provides attachment points for the costal cartilages of the third through seventh pairs of ribs.
The smallest and most inferior part of the sternum is the xiphoid process, meaning “sword-shaped.” This pointed projection is primarily cartilaginous in younger individuals and gradually ossifies, or turns into bone, with age, typically by around 40 years. Its shape and size can vary considerably among individuals.
Role in the Body
The sternum serves a primary function in safeguarding organs within the thoracic cavity. Together with the ribs, it forms a protective cage that shields the heart, lungs, and major blood vessels from external physical impact.
The sternum also functions as a central anchor for the rib cage. The ribs connect to the sternum via cartilage, creating a structured yet flexible framework. This integrated system allows for the necessary movements of the chest wall during respiration.
Through its connections to the ribs and certain muscles, the sternum contributes to the mechanics of breathing. While the sternum itself does not directly move the chest or torso, the cartilage linking it to the ribs enables minor motions with each breath. This arrangement provides a stable base for various muscles of the chest and abdomen.