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Recommended video: Sternum [09:33]
Bony elements of the sternum.

The sternum is the bone that lies in the anterior midline of our thorax. It forms part of the rib cage and the anterior-most part of the thorax. Its functions are to protect the thoracic organs from trauma and also form the bony attachment for various muscles. It is also the center around which the superior 10 ribs directly or indirectly attached.

There are certain congenital pathological conditions related to the sternum. They mostly refer to the deviations of the shape of the sternum, which in some cases, especially if it is an extreme deviation, can affect the organs within thoracic cavity.

Key facts about the sternum
Function Protection of the lungs, heart and thoracic blood vessels from mechanical damage
Embryological development Develops from a left and right cartilaginous plates that unite in the midline
Parts Manubrium - most superior region that articulates with clavicles and the first pair of ribs
Body - articulates with 3rd - 7th ribs
Xiphoid process - most inferior part
Clinical relations Sternotomy, sternoclavicular joint dislocation, fracture, pectus excavatum, pectus carinatum

In this article, we will discuss the embryology, anatomy and clinical relevance of the sternum.

  1. Embryology
  2. Anatomy
    1. Manubrium
    2. Body of the sternum
    3. Xiphoid process
  3. Clinical points
    1. Sternotomy/cardiothoracic surgery
    2. Sternoclavicular joint dislocation
    3. Sternal fracture
    4. Bone marrow biopsy
    5. Pectus excavatum
    6. Pectus carinatum
  4. Sources
+ Show all


  • The sternum develops from a left and right cartilaginous plates that unite in the midline.
  • The ribs develop from their ossification centers and unite with the sternum in the midline.
  • The manubrium and xiphoid process usually develop from one ossification centre each, but the sternebral centres are commonly paired either symmetric or asymmetric.
  • The xiphoid process does not fully join the body of the sternum until adulthood.


The word sternum originates from the ancient Greek word ‘sternon’, meaning chest. The sternum is also known as the breastbone. It is a flat bone that articulates with the clavicle and the costal cartilages of the upper 7 ribs (true ribs), while the 8th, 9th and 10th ribs (false ribs) are indirectly attached with sternum via costal cartilage of the ribs above. The bone is divided into three parts:

  1. The manubrium.
  2. The body of the sternum (mesosternum).
  3. The xiphoid process (xiphisternum).

The sternum lies very superficially in the anterior thorax and is easily palpable below the skin of the chest in the midline. The bone covers and protects the heart and great vessels in part, as well as the trachea and esophagus.

Test what you already know about the sternum with the following quiz:


The manubrium is a large quadrangular shaped bone that lies above the body of the sternum. The lower border is narrower, is quite rough, and articulates with the body with a thin layer of cartilage in between. At the superior border of the bone is the jugular notch or suprasternal notch, fibers of interclavicular ligaments are attached here. The clavicular notches for the articulation of clavicles are projected upward and laterally on both sides of the jugular notch. The costal cartilages of the first rib and part of the second rib also articulate with the manubrium, and they fit into facets on its lateral border.

The sternal fibers of pectoralis major and sternocleidomastoid are attached to the anterior surface. Posterior surface gives attachment to sternohyoid and sternothyroid muscles. The superior sternopericardial ligament connects the pericardium (that lies in the superior part of the middle mediastinum) to the manubrium. The lower border of the manubrium articulates with the body of the sternum at the sternal angle (of Louis), it is where the second pair of costal cartilage attaches to the sternum and at the level of the inferior border of T4, is also clinically known as the Angle of Louis. The second intercostal space can be palpated on either side of this projection and is the location for auscultation of the pulmonary and aortic area on left and right respectively.

Sternum in cadaver: Notice how manubrium articulates with the clavicle via the clavicular notches and with the first rib at its lateral surface.

Body of the sternum

The body of the bone (also known as the gladiolus) is a long flat structure, with a convex anterior surface, and a concave posterior surface. It has facets on each of its lateral borders for articulation with the costal cartilage of the 3rd to 7th ribs along with part of the second costal cartilage.

The sternocostal head of the pectoralis major muscle attaches the sternum, on the lateral sides of its anterior surface. The posterior surface of the body gives rise to the transversus thoracis muscle (innervated by intercostal nerves). The lower part of the bone is narrower and articulates with the xiphoid process.

Xiphoid process

The xiphoid process is a small projection of bone which is usually pointed. It possesses demifacets for part of seventh costal cartilage at its superolateral angle.

The fibres of rectus abdominis and aponeurosis of internal and external obliques are attached to its anterior surface. Posterior surface gives rise to the inferior sternopericardial ligament.

It also is the site of insertion of part of the thoracic diaphragm. Blood supply to the sternum arises from the internal thoracic artery.

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