XIPHOID PROCESS: CHARACTERISTICS, FUNCTION, ALTERATIONS, DISORDERS - ANATOMY AND PHYSIOLOGY - 2024

The xiphoid process or xiphoid process is the most caudal (lower) and smallest part of the sternum. The sternum is a flat bone that is part of the anterior bony structure of the thorax in which the costal arches articulate at their anterior joint.

This bone has three parts that, in the cranio-caudal sense, are: the manubrium, the body and the xiphoid appendix. The xiphoid appendix is ​​highly variable in shape and size. It can be perforated, bifid or flat with a more or less triangular shape and its structure is thinner than that of the body of the sternum.

Sternum with xiphoid appendix. (Source: Anatomography via Wikimedia Commons)

In adults, the xiphoid appendix is ​​formed by a hyaline cartilage that surrounds a central bone portion, the size of this bone portion increases with age. In the ventral position, the xiphoid appendix can be palpated and even a small depression can be observed, which is called an “epigastric depression”.

The xiphosternal joint can be seen as a horizontal ridge located above the ventral epigastric depression and corresponds to the apex of the subcostal angle. The lower edge of the body of the sternum, where the xipho-sternal joint is located, is made up of fibrocartilage that coalesces in old age.

The xiphoid process or process is a very vulnerable part of the sternum, which is why it is considered a very important target in martial arts.

General characteristics

The xiphoid appendix name derives from the Greek word "xiphos", which means sword. This appendix is ​​also called the "laughing bone." It has a front and a back face, two side edges and a top or base end and a bottom or vertex.

It is the bone with the greatest variability in shape and size in the human anatomy. Its length ranges from 40 to 80 mm (with an average of 30 mm) and a width, in its largest diameter, from 15 to 22 mm. Very varied shapes have been described: wide and thin, triangular, pointed, bifid, curved forward or backward, to the right or left, perforated, rhomboid or oval.

Xiphoid Appendix (Source: Database Center for Life Science (DBCLS). Via Wikimedia Commons)

Clinically and semiologically, this appendix constitutes an anatomical landmark in the thorax. It is the lower limit of the thoracic cavity, it is a point of reference for the location of the diaphragm, the diaphragmatic aspect of the liver, the lower limit of the heart and the midline of the thorax.

The xiphoid appendix is ​​the site of insertion of several muscle groups such as the diaphragm (one of the sites of bone insertion), some muscles of the anterior wall of the abdomen, and a muscle located in the internal and internal part of the anterior chest wall. the triangular muscle of the sternum.

The triangular muscle of the sternum or transverse muscle of the thorax has its point of origin on the posterior aspect of the xiphoid appendix, in the lower third of the body of the sternum and in this last area at the sternal ends of the corresponding costal cartilages.

It is inserted, by means of thin and wide muscular bands, on the inner faces of costal cartilages II or III to VI. Its function is to depress the costal cartilages, taking its original attachments as a support point. This muscle contracts during forced expiration.

Function

Its functions are related to the muscles, ligaments and costal cartilages that are inserted into it. The muscles that attach to the xiphoid appendix fulfill different functions in the respiratory cycle, which is why it shares these functions with them.

However, being part of the sternum, it constitutes one of the bones that make up the rib cage and that protect the vital organs housed in it, such as the heart, lungs and great vessels.

The different structures attached to the xiphoid process and their related function are listed below.

Upper xiphoid area

It joins the body of the sternum and, on the lateral aspect of both sides, joins the cartilage of the seventh costal arch. It has a structural function in the chest wall and a protective one.

Anterior zone of

The anterior costoxiphoid ligaments on each side and the rectus abdominis muscle are inserted. It allows to fix some rib arches and is a support point for the function of this muscle. It is an expiratory muscle, but it also contributes to the flexion of the trunk.

Posterior xiphoid area

It is the area of ​​insertion of the posterior costoxiphoid ligaments, the diaphragm and the transverse muscle of the chest. Participate with these in the two phases of the respiratory cycle. In inspiration through the diaphragm and in forced expiration through the transverse thorax.

Lateral xiphoid area

The aponeurosis of the abdominal muscles is inserted.

Lower xiphoid area

It is the site of insertion of the linea alba of the abdomen, a collagenous connective tissue structure formed by the fusion of the aponeurosis of the muscles of the anterior abdominal wall that separates the right and left rectus abdominis.

The xiphoid appendix is ​​used as a reference for cardiopulmonary resuscitation maneuvers. In these cases, the pressure that must be exerted on the thorax should be done on the body of the sternum and not on the xiphoid, since the xiphoid, the diaphragm or the liver can be injured.

Alterations and disorders

Like any tissue or organ in the human body, this bone can suffer trauma, inflammations, infections, tumors, among other pathological processes.

Being a very superficial structure, trauma to the sternum frequently generates fractures of the xiphoid appendix, which causes pain, local edema and, occasionally, respiratory problems.

Perforated xiphoid appendix (Source: User: Brace via Wikimedia Commons)

Although xiphoid fractures do not endanger the life of the patient, on some occasions due to the proximity of vital organs, perforations can occur, the most frequent are pulmonary perforations. In these cases emergency care is necessary.

There is a nosological entity called xiphoid syndrome that is characterized by pain, inflammation, tenderness and discomfort in the xiphoid appendix. Pain can be reflected in the shoulders and chest.

This syndrome can accompany traumatic events in the area, but is also associated with gastroesophageal reflux, gallbladder problems, some heart problems, among others. It is then necessary to make the differential diagnosis.

The xiphoid appendix, like the sternum and other bones of the human skeleton, can be subject to tumors of origin or metastatic. Sternal metastases are not very frequent, and can occur by continuity or at a distance. One of the tumors that can invade the sternum is hepatocellular carcinoma.

References

1. Flament, D., Goldsmith, P., Buckley, CJ, & Lemon, RN (1993). Task dependence of responses in first dorsal interosseous muscle to magnetic brain stimulation in man. The Journal of Physiology, 464 (1), 361-378.
2. Gardner, E., J Gray, D., & O'Rahilly, R. (1963). Anatomy: a regional study of human structure. WB Saunders.
3. González-Flores, V., Alcántara-Vázquez, A., Hernández-González, M., Pérez-Espinoza, J., & Ortiz-Hidalgo, C. (2007). Sternal metastases as first presentation of hepatocellular carcinoma. A case report. Medical Journal of the General Hospital of Mexico, 70 (4), 184-188.
4. Netter, FH (1983). The ClBA Collection of Medical Illustrations,
5. Putz, R., & Pabst, R. (2006). Sobotta-Atlas of Human Anatomy: Head, Neck, Upper Limb, Thorax, Abdomen, Pelvis, Lower Limb; Two-volume set.
6. Standring, S. (Ed.). (2015). Gray's anatomy ebook: the anatomical basis of clinical practice. Elsevier Health Sciences.