Sternum
A long flat bone forming the front of the rib cage.
The sternum, also known as the breastbone, is a long flat bone located in the central part of the chest. It connects to the ribs via cartilage and forms the front of the rib cage, helping to protect the heart, lungs, and major blood vessels from injury. Shaped roughly like a necktie, it is one of the largest and longest flat bones of the body, consisting of three regions: the manubrium, the body, and the xiphoid process.
- Type
- Flat bone
- Location
- Central part of the chest
- Regions
- Manubrium, body (gladiolus), xiphoid process
- Function
- Protects heart, lungs, and major blood vessels; supports clavicles; attaches to ribs via cartilage
- Etymology
- From Ancient Greek στέρνον (stérnon) 'chest'
Lore & Background
The sternum is a narrow, flat bone forming the middle portion of the front of the chest. Its top supports the clavicles and its edges join with the costal cartilages of the first two pairs of ribs. The inner surface attaches the sternopericardial ligaments, and its top connects to the sternocleidomastoid muscle. In its natural position, the sternum is angled obliquely, downward and forward, and is usually longer in males than in females. The manubrium is the broad upper part, quadrangular in shape, with a suprasternal notch in the middle. It joins with the body at the sternal angle, which can be palpated on the surface. The body, or gladiolus, is the longest part, flat on the front and marked by three transverse ridges. The xiphoid process is the pointed inferior end; improper chest compressions during CPR can cause it to snap off, driving it into the liver and causing fatal hemorrhage. The sternum develops from two cartilaginous bars that fuse, ossifying from six centers: one for the manubrium, four for the body, and one for the xiphoid process. Ossification begins in the sixth month of fetal life and continues through the eighteenth year. Union of the body's centers begins about puberty and is complete by age 25, with development completed earlier in females than in males.
Reader's Guide
The sternum is a critical structural and protective component of the human chest. As the central anchor of the rib cage, it shields the heart, lungs, and major blood vessels from trauma while providing attachment points for the clavicles, ribs, and several muscles, including the pectoralis major and transversus thoracis. Its three-part structure—manubrium, body, and xiphoid process—allows for flexibility and articulation with the costal cartilages of the first seven ribs, forming the sternocostal joints. The sternal angle, where the manubrium meets the body, serves as a key anatomical landmark for locating the second rib during physical examinations. Variations in the sternum are common, including a sternal foramen in 2.5–13.5% of the population, fusion of the manubriosternal joint in about 5%, and occasional episternal ossicles. The xiphoid process may remain ununited into old age, and the manubrium may join the body by bone only superficially in advanced life. Understanding these variations is important for medical procedures such as CPR, where improper technique can fracture the xiphoid process, and for interpreting imaging studies. The sternum's development from multiple ossification centers explains rare malformations like fissura sterni. Its role as both a protective shield and a structural keystone underscores its significance in human anatomy and clinical practice.
Did You Know?
- The word sternum originates from Ancient Greek στέρνον (stérnon) meaning 'chest'.
- Improperly performed chest compressions during CPR can cause the xiphoid process to snap off, driving it into the liver and causing fatal hemorrhage.
- In 2.5–13.5% of the population, a sternal foramen may be present at the lower third of the sternal body.
- The sternum is usually longer in males than in females.
Frequently Asked Questions
What is the Sternum?
The Sternum, commonly called the breastbone, is a long flat bone that sits at the very center of the chest. It is one of the body's largest flat bones and is shaped a bit like a necktie.
Where exactly is the Sternum located and how does it connect to other bones?
It occupies the midline of the front chest wall, anchoring to the ribs through cartilaginous joints. It also serves as the attachment point for the clavicles, linking the shoulder girdle to the thorax.
What is the Sternum's main job in the body?
Its primary role is shielding the heart, lungs, and the great blood vessels from external trauma. By forming the anterior wall of the rib cage, it creates a rigid yet slightly flexible barrier around these vital organs.
What are the three named regions of the Sternum?
From top to bottom, the bone is divided into the manubrium, the long central body (sometimes called the gladiolus), and the small pointed xiphoid process at the base. Each region serves as an attachment site for different muscles, ligaments, and ribs.
Where does the name 'Sternum' come from?
The term traces back to the Ancient Greek word στέρνον (stérnon), which simply means 'chest.' This etymology reflects the bone's central, defining position in the thoracic region.
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