The breastbone, scientifically known as the sternum, is a flat bone located in the central part of the chest. It is situated at the front of the rib cage. This bone plays an important role in the body’s structure and overall function.
Anatomy and Position
The sternum is a T-shaped or sword-shaped bone positioned vertically in the anterior midline of the thorax. It measures approximately 6 inches (15 cm) long. The sternum is composed of three distinct parts: the manubrium, the body, and the xiphoid process.
The manubrium is the uppermost and broadest section of the sternum, resembling a handle. It has a trapezoid or quadrangular shape, wider at the top, and includes a concave superior aspect known as the jugular notch. The manubrium articulates with the clavicles (collarbones) at its superior lateral edges. This part also connects to the costal cartilages of the first pair of ribs and partially to the second pair.
The body of the sternum is the largest and longest section, flat and elongated. It articulates superiorly with the manubrium at the sternal angle, a palpable ridge where the second pair of ribs attach. Along its lateral edges, the body features articular facets that connect with the costal cartilages of the third through seventh ribs.
The xiphoid process is the smallest and most inferior part of the sternum, typically pointed and variable in shape and size. It is primarily cartilaginous in early life, gradually ossifying (turning into bone). The xiphoid process can articulate with a portion of the seventh rib’s costal cartilage.
Key Roles
The breastbone plays several roles in the human body, primarily providing protection and serving as an attachment point. Its flat, sturdy structure forms a barrier for the organs within the thoracic cavity. This includes safeguarding the heart, lungs, and major blood vessels from external injury or trauma. The sternum’s design, along with the ribs, creates a protective cage that allows for the expansion and contraction of these organs during respiration.
The sternum also serves as an attachment site for bones and muscles. It connects directly to the ribs via costal cartilages, forming the anterior part of the rib cage. The first seven pairs of ribs directly articulate with the sternum. Several muscles of the chest, neck, and abdomen attach to different parts of the sternum, including the pectoralis major, sternocleidomastoid, sternohyoid, sternothyroid, and the diaphragm. These muscular attachments aid functions like breathing and stabilizing the torso.