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Sternum

life science Maturity 11-13 Next article →

The sternum, often called the breastbone, is a long, flat bone located in the center of the chest.

Body of sternum - close-up - animation
Body of sternum - close-up - animation

It serves a vital role in the human body by forming the front of the rib cage. This structure helps protect delicate organs like the heart, lungs, and major blood vessels from injury. The sternum is one of the largest and longest flat bones in the human body. Its name comes from the Ancient Greek word *stérnon*, which means "chest."

Xiphoid process - close-up - animation
Xiphoid process - close-up - animation

The sternum is composed of three distinct anatomical regions. At the very top is the manubrium, a term derived from Latin meaning "handle."

Manubrium - animation
Manubrium - animation

This part is broad and quadrangular, featuring a central indentation called the suprasternal notch. Below the manubrium lies the body, or gladiolus, which is the longest part of the bone. The body is flat and features three transverse ridges on its front surface. Finally, the lowest part is the xiphoid process, a small and pointed structure at the inferior end.

Xiphoid process - close-up - animation
Xiphoid process - close-up - animation

These three parts connect to the rest of the skeletal system through specific joints. The manubrium supports the clavicles, or collarbones, at its top edges. It also joins with the costal cartilages of the first one and a half pairs of ribs. The body of the sternum connects to the second through the sixth ribs via costal cartilages. The sternal angle is a crucial landmark located where the manubrium meets the body. This angle is where the second rib attaches, making it easy for doctors to locate during physical exams.

Medusterdisloca
Medusterdisloca

Development of the sternum involves a complex process called ossification, where cartilage turns into bone.

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Gray118

It begins as two cartilaginous bars on the left and right sides of the chest. These bars eventually fuse together along the middle to create a single bone. The sternum forms from six different ossification centers. One center forms the manubrium, one forms the xiphoid process, and four centers form the body. These centers appear in a specific sequence, starting in the sixth month of fetal life.

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Gray119

Growth patterns for the sternum vary based on age and biological sex. The ossification centers in the body begin to fuse around the time of puberty. By age 25, most of these segments have fully united into one bone. Females generally complete this development earlier than males. The xiphoid process is the slowest to finish, sometimes remaining ununited even into old age. Interestingly, the xiphoid process might not join the main body until after a person reaches age 40.

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Gray120

While most people have a standard sternum, some anatomical variations exist. Between 2.5% and 13.5% of people have a sternal foramen, which is a small hole in the lower body. This hole is present from birth and is often located to the left or right of the center.

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Gray121

Other rare variations include the presence of small bones called episternal ossicles or a vertical fissure known as *fissura sterni*. These variations are usually harmless, though they can be noted by doctors during medical procedures.

Because of its location and composition, the sternum is significant in clinical medicine. The bone contains highly vascular tissue, meaning it has a rich blood supply. This makes it a useful site for a bone marrow biopsy, especially for patients with a high BMI. In major surgeries, such as cardiothoracic surgery, doctors may perform a median sternotomy. This involves cutting the sternum open to access the heart. Surgeons then use wire cerclage or metal plates and screws to fix the bone back together.

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🖼️ Images & Media (8)
File:Manubrium - animation.gif
Manubrium - animation.gif
File:Body_of_sternum_-_close-up_-_animation.gif
Body_of_sternum_-_close-up_-_animation.gif
File:Xiphoid_process_-_close-up_-_animation.gif
Xiphoid_process_-_close-up_-_animation.gif
File:Gray118.png
Gray118.png
File:Gray119.png
Gray119.png
File:Gray120.png
Gray120.png
File:Gray121.png
Gray121.png
File:Medusterdisloca.png
Medusterdisloca.png
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