The sternum, often called the breastbone, is a flat, dagger-shaped bone positioned in the center of the chest. This bone forms an important part of the rib cage, connecting to the ribs via cartilage and forming the front of the thoracic cavity. It provides structural support and protects organs like the heart and lungs from impact.
Identifying the Xiphoid Process
The smallest and lowest part of the sternum is known as the xiphoid process. Its name originates from the Greek word “xiphos,” meaning sword, which aptly describes its typically pointed shape. While often appearing pointed, the xiphoid process can exhibit anatomical variation among individuals, sometimes appearing bifid (split), perforated, or curved.
Located at the inferior end of the sternum, below the body, the xiphoid process is an important anatomical landmark. In early life, this structure is composed entirely of cartilage, providing it with flexibility. It remains cartilaginous for years before gradually undergoing a process of ossification.
Function and Developmental Changes
The xiphoid process serves as an attachment point for several important muscles and ligaments, and does not play a significant structural role in the rib cage. For instance, it provides an origin point for some fibers of the diaphragm, a key muscle involved in breathing. Additionally, muscles like the rectus abdominis, part of the abdominal wall, also connect to the xiphoid process.
Developmentally, the xiphoid process gradually transforms from cartilage to bone. This ossification process typically begins in late adolescence or early adulthood, with the xiphoid process usually fusing with the body of the sternum between the ages of 15 and 29. However, the exact timing and extent of fusion vary widely among individuals. As a result, its shape and size can also differ significantly among individuals, even in adulthood.
Clinical Significance
Knowledge of the xiphoid process is important in medical contexts, especially for procedures like cardiopulmonary resuscitation (CPR). During CPR, correct hand placement is essential. Pressure should be applied to the lower half of the sternum, just above the xiphoid process. Direct pressure on the xiphoid process should be avoided to prevent potential injury.
Improper hand placement during CPR or blunt trauma to the chest can lead to complications involving the xiphoid process. Direct force can cause inflammation, known as xiphodynia, resulting in localized pain and tenderness. In more severe cases, trauma might lead to a fracture or detachment of the xiphoid process, risking underlying organs like the liver or diaphragm. Beyond emergency procedures, the xiphoid process also serves as a recognizable anatomical landmark for surgical procedures and diagnostic imaging.