Sternum Anatomy: Manubrium, Body (Gladiolus), and Xiphoid Process
In this anatomy lesson, I’m going to cover the sternum bone, also called the breastbone. I like to call this the “necktie bone” because it is shaped just like a necktie, and it’s also located in the center of the chest. In fact, the word sternum comes from a Greek word that literally means “chest.”
The sternum is classified as a flat bone, and it makes up part of the axial skeleton. It articulates with the medial end of the clavicle bones, as well as the costal cartilages of the true ribs (ribs 1-7).
The sternum’s long, flat shape provides protection for the important organs located within the thoracic cage, and it also provides attachment for various muscles such as the pectoralis major muscles and the diaphragm.
The sternum has three main sections that you should know for anatomy exams: the manubrium, the body (gladiolus), and the xiphoid process. The letters MBX, just like the Honda motorcycle brand, can help you remember the order of the parts of the sternum (from top to bottom).
These parts are named after ancient words that refer to parts of a sword:
- The manubrium comes from a word that means “handle”
- The gladiolus (body) comes from a word meaning “sword”
- Xiphoid comes from an ancient word that means “straight sword”
The manubrium is the quadrangular-shaped portion that is located at the superior (upper) region of the sternum, resembling the knot part of a necktie. There are a few important landmarks on the manubrium. First, if you look at the superior border, you’ll notice a notched area in the center, which is called the jugular notch or suprasternal notch. This notch is visible on the neck and can be palpated and used as a landmark.
On each side of the jugular notch, we have the clavicular notches, which articulate with the sternal end of the clavicle bones to form the sternoclavicular joint. Ribs one and two articulate with the manubrium, but rib two articulates with only a partial facet of the manubrium at the sternal angle.
Gladiolus Anatomy (Body of Sternum)
The manubrium attaches to the body of the sternum, or gladiolus, at a transverse ridge, forming the sternal angle (also known as the angle of Louis). This is the point where the 2nd pair of ribs attach to the sternum, with articulation at a partial facet, or demifacet, on the manubrium and another partial facet on the body of the sternum.
The sternal angle is an important landmark for nurses and other healthcare professionals because it will help you locate and identify the intercostal space of each rib, which is helpful when locating the apical pulse or for listening to heart sounds or lung sounds during assessments. (The apical pulse is located at the midclavicular line of the 5th intercostal space, as demonstrated by Nurse Sarah in our Apical Pulse Assessment video.)
On each side of the sternum’s body, you’ll notice several other facets or notches, which allow for the attachment of the costal cartilages of ribs 2-7. However, the facet for rib seven is usually shared by both the body and xiphoid process, with each part containing only a partial facet.
Xiphoid Process Anatomy
The inferior part of the sternum is called the xiphoid process. Whenever you see the word “process” on a bone, it’s referring a projection coming off the bone. That’s what this part is: a little projection coming off the inferior portion of the sternum.
The xiphoid process is made of cartilage until around middle age, at which point it finally becomes bone. It is located around the 9th thoracic vertebra, and it allows for the the attachment of the seventh rib via costal cartilage, as well as important muscles such as the diaphragm.
The xiphoid process also serves as an important landmark when performing CPR. Before delivering chest compressions, you need to locate the xiphoid process at the end of the sternum so that you can avoid putting pressure on it during chest compressions. You’ll want to place your palm on the body of the sternum, not the xiphoid process, as it can break off and puncture organs.
Free Quiz and More Anatomy Videos
Take a free sternum anatomy quiz to test your knowledge, or review our sternum anatomy video. In addition, you might want to watch our anatomy and physiology lectures on YouTube, or check our anatomy and physiology notes.