What are the three main parts of the sternum?

The sternum is composed of three distinct parts: the manubrium sterni (episternum) as the upper part, the body (mesosternum) as the middle and largest part, and the xiphoid process (metasternum) as the lowest and smallest part.

What is the sternal angle and why is it important?

The sternal angle (Angle of Louis) is a palpable bony ridge at the manubriosternal junction. It serves as a key anatomical landmark for structures like the articulation of the 2nd costal cartilage, tracheal bifurcation, and division between the superior and inferior mediastinum.

Which muscles attach to the manubrium of the sternum?

The manubrium has several muscle attachments: on the anterior surface, the sternal head of sternocleidomastoid and pectoralis major; on the posterior surface, sternohyoid and sternothyroid muscles.

What are the clinical conditions associated with the sternum?

Common clinical conditions include funnel chest (pectus excavatum) with a depressed sternum, pigeon chest (pectus carinatum) with a projecting sternum, and sternal fractures often at the sternal angle from trauma. Other issues are sternal foramen or cleft sternum due to fusion failure.

How does the sternum develop and ossify?

The sternum develops from cartilaginous plates that fuse. Ossification centers appear at different times: manubrium at 5th month in utero, body in four sternebrae from 6th to 9th month, and xiphoid around 3rd year of life. Fusion of sternebrae completes by age 25, and xiphoid fuses with the body around age 40.

What is the function of the sternum in the thoracic cage?

The sternum serves as an important site for articulation with ribs and attachment for muscles of the thorax and neck, such as pectoralis major and the diaphragm. It helps form the anterior chest wall, providing structural support and protection for underlying organs.

Sternum Anatomy – Manubrium, Body, Xiphoid & Sternal Angle