The xiphoid process is the smallest and most inferior region of the sternum, or breastbone. At birth, it is a thin, roughly triangular region of cartilage that slowly ossifies into a bone and fuses with the body of the sternum. Clinically, the xiphoid process plays an important role as a bony anatomical landmark in the trunk and may be damaged by improperly administered CPR.
The xiphoid process is located inferior to the body of the sternum. The word xiphoid comes from the Greek word for “sword-shaped,” which describes its thin and pointed shape. It is widest at its superior end where it is attached to the body of the sternum by a thin, slightly movable fibrous joint (syndesmosis). From its syndesmosis, it tapers gradually to a point. There are many common variations in the shape of the xiphoid process, including:
- Perforation with a small foramen in its center
- Bifurcation with a split into left and right branches at its inferior end.
These variations in anatomy apparently do not result in any sort of change in the function of the xiphoid process and may be inherited genetically.
Developmentally, the xiphoid process begins as a structure made of hyaline cartilage at birth and childhood, slowly ossifying into a bony part of the sternum. In fact, the ossification of the xiphoid process is so slow that it often does not end until an individual reaches the age of 40.
The xiphoid process functions as a vital attachment point for several major muscles. It acts as one of several origins for the diaphragm muscle that forms the floor of the ribcage and performs the vital process of respiration. The xiphoid process also acts as an insertion for the rectus abdominis and transverse abdominis muscles that compress and flex the abdomen. During cardiopulmonary resuscitation (CPR), the xiphoid process may be used as a bony landmark to determine the location for administering chest compressions. It is extremely important that pressure is not exerted on the xiphoid process during chest compressions, as this can cause the xiphoid process to separate from the sternum, possibly puncturing the diaphragm or liver.