Why Is the Sternum Important in Human Biology?
The word sternum refers to the chest, and if you carefully look at the structure of the sternum or breastbone, it looks like a necktie. The human body is a complex structure, and it contains a lot of bones, muscles, and other organs. The sternum location is between the chest and, therefore, also known as the breastbone. Sternum plays a significant role in protecting all the organs near the torso area and also is a connection point of several bones and muscles.
In this article, we have discussed the structure of sternum along with its anatomy and functions.
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Structure and Anatomy of Sternum
The structure of the sternum contains the following three sternum parts.
Manubrium: the first part of the sternum is the manubrium, which is the top part and includes your collar bone. At this, the top most ribs connect, and the bottom of the Manubrium shares a border with the other parts of the sternum. At the bottom of it, your second set of ribs of your body also connects.
Body: the middle part of the sternum is also known as the body, and it’s the longest part. It connects with manubrium at the top and the Xiphoid process at the bottom. You have often heard the word cartilage that is present in this part of the sternum, and here your third set of ribs to the seventh set connects with the help of cartilage.
Xiphoid process: the bottom part of the sternum is known as the Xiphoid process. The shape of this part can differ from individual to individual, and as your age increases, the Xiphoid process of the sternum slowly begins to calcify.
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Functions of Sternum
One of the significant functions of the sternum is to protect lungs, blood vessels, and heart from any kind of injury, and it’s one of the longest and largest flat bones present in our body. There are major two functions of the sternum in our body, and those are as follows.
Support: one of the most significant functions of the sternum is providing support to the chest and upper abdomen of our body. It provides support to the rib cage, and collar bone of your body, and many other parts of your skeleton system.
Protection: the sternum is present in the centre of your chest, and there are many organs near these areas, such as the heart, lungs, blood vessels, etc., so it protects them from all kinds of injury.
When Can the Sternum Break?
Many times it even happens that a break in the sternum can cause a lot of health problems. Most of the time, it’s noticed that the break can cause trouble related to different issues in the chest. Some of the causes of the broken sternum are as follows.
Car Accidents: car accidents can be a major reason for broken of the sternum, and it can be caused by multiple reasons such as high-impact sports, falling from a large height, and other reasons.
Other Reasons:- Another reason for a sternum is postmenopause, having osteoporosis, and adults have more chances of these problems.
Did You know?
There are many bones inside our body that we can feel by touching it and Sternum is one of them. It’s lying between your chest, and you can feel it with your fingers, and it’s a flat bone in the centre of your torso. The large dip present in the neck of humans is known as a jugular notch.
FAQs on Sternum: Anatomy, Structure & Function
1. What is the sternum and what are its primary functions in the human body?
The sternum, commonly known as the breastbone, is a flat, T-shaped bone located in the anterior midline of the chest. It forms a crucial part of the axial skeleton. Its primary functions include:
- Protection: It acts as a shield, protecting the vital thoracic organs beneath it, such as the heart and lungs, from injury.
- Support: It serves as the central anchoring point for the rib cage, connecting the ribs via cartilage.
- Attachment: It provides an attachment point for various muscles, as well as for the clavicles (collarbones).
2. What are the three main parts of the human sternum?
The human sternum is anatomically divided into three distinct parts, arranged superiorly to inferiorly:
- Manubrium: The uppermost and widest part of the sternum. It articulates with the clavicles and the costal cartilages of the first and second ribs.
- Body (Gladiolus): The middle and longest part. It connects with the costal cartilages of ribs two through seven.
- Xiphoid Process: The lowermost and smallest part. It is cartilaginous in youth and typically ossifies (turns to bone) in adulthood.
3. How does the sternum connect with the ribs and clavicles to form the rib cage?
The sternum is the central pillar of the anterior rib cage. The manubrium has clavicular notches on its superolateral sides where the clavicles (collarbones) articulate, forming the sternoclavicular joints. The first seven pairs of ribs, known as true ribs, connect directly to the sternum via their respective costal cartilages. This connection provides a strong yet flexible framework that protects the thoracic organs while allowing for respiratory movements.
4. What is the significance of the manubrium of the sternum?
The manubrium is the superior portion of the sternum and is highly significant for its articulations. It connects with the clavicles, forming the only direct bony link between the pectoral girdle (shoulder) and the axial skeleton. It also articulates with the first pair of ribs and the upper part of the second pair. The palpable U-shaped depression on its superior border is known as the jugular notch or suprasternal notch.
5. How does the structure of the sternum facilitate the mechanism of breathing?
The sternum plays a vital, passive role in breathing. During inhalation, the contraction of the intercostal muscles elevates the ribs and thrusts the sternum forward. This increases the anteroposterior diameter of the thoracic cavity, allowing the lungs to expand. During exhalation, the muscles relax, and the sternum and ribs return to their original position, decreasing thoracic volume and helping to expel air. The cartilaginous connections provide the necessary flexibility for this movement.
6. Why is the xiphoid process initially cartilaginous and what is its role?
The xiphoid process remains as cartilage for a significant portion of early life and typically does not fully ossify until around age 40. This initial flexibility is important as it reduces the risk of it fracturing and damaging underlying organs like the liver or diaphragm during impacts or chest compressions. Its primary role is to serve as an attachment point for several important muscles, including the abdominal diaphragm (essential for breathing) and the rectus abdominis muscles.
7. What makes the sternum so important for protecting the heart?
The sternum's location in the direct anterior midline of the thorax makes it the primary bony shield for the heart, which lies immediately behind it. In the event of a frontal impact, the broad, flat surface of the sternum absorbs and distributes the force, significantly reducing the risk of direct trauma to the heart and major blood vessels like the aorta and vena cava. This protective function is critical for survival.
8. Is the sternum considered a single bone or does it develop from multiple parts?
While the sternum functions as a single bone in adults, it is not a single developmental unit. It develops from the fusion of multiple cartilaginous segments called sternebrae. This developmental origin is why the adult sternum retains its three distinct sections: the manubrium, the body (itself formed from the fusion of about four sternebrae), and the xiphoid process. This segmental development is a key concept in understanding skeletal anatomy.
