The sternum, often called the breastbone, is a vital long, flat bone located centrally in your chest. Its primary role is to safeguard the critical organs situated behind it, most notably the heart. But Where Is Your Sternum exactly, and what else does it do? This bone is more than just a shield; it’s a cornerstone of your chest structure, supporting surrounding bones and muscles and playing a key part in breathing.
Understanding the sternum’s anatomy, location, and function is crucial for appreciating its importance to your overall health. Like any bone in your body, the sternum can be susceptible to conditions and injuries. Knowing how to maintain its health and recognize potential issues is essential.
Anatomy of the Sternum: A Three-Part Bone
The sternum isn’t a single piece but is composed of three distinct sections that fuse together during development. This vertical, T-shaped bone at the front of your chest is divided into:
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Manubrium: This is the uppermost section of the sternum. It’s a broad, roughly quadrilateral-shaped segment. At the top of the manubrium is the suprasternal notch, a U-shaped indentation you can feel at the base of your neck. On either side of the manubrium are clavicular notches, where your collarbones (clavicles) attach to form the sternoclavicular joints – part of your shoulder structure and also where the first pair of ribs connect.
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Body: The manubrium connects to the body of the sternum at the sternal angle, a slightly raised horizontal ridge that is a palpable landmark. This is also the point where the cartilage of the second rib attaches. The body is the middle and longest portion of the sternum. It’s flat and features shallow depressions along its sides. These are where the cartilage from the third through seventh pairs of ribs connects, forming the costosternal joints.
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Xiphoid Process: The final, most inferior part of the sternum is the xiphoid process. This is a small, triangular piece of bone that projects downwards. Interestingly, the xiphoid process varies significantly in size and shape from person to person. In children and young adults, it’s primarily made of cartilage. Around the age of 40, it begins to ossify, or harden into bone. By age 60, the xiphoid process is typically largely calcified.
Location: Centrally Positioned in Your Chest
Where is your sternum located in relation to other parts of your body? The sternum sits at the midline of your anterior chest wall. Imagine a line running vertically down the center of your chest; the sternum is positioned along this line.
The sides of the sternum are connected to the ribs via costal cartilage. This flexible cartilage is crucial because it allows the rib cage to expand and contract during breathing. It also provides some cushioning to protect the chest from impact.
Several significant muscles attach to the sternum. These include muscles of the neck, thorax, and abdominal wall, highlighting its role in musculoskeletal structure. The pectoralis major, the large muscle of the chest, attaches to the body of the sternum. Importantly, the diaphragm, the primary muscle for breathing, attaches to the xiphoid process.
Anatomical Variations of the Sternum
While the basic structure of the sternum is consistent, there are common anatomical variations. It’s worth noting that people assigned female at birth tend to have a thinner sternal body. Most other variations occur in the lower portion of the sternum, specifically the xiphoid process.
Common sternal variations include:
- Bifid Xiphoid: Instead of a single triangular tip, the xiphoid process has two separate points or endings. This is a common variation and usually harmless.
- Sternal Angle Misplacement: If the sternal angle is not in its typical position, it can lead to errors when counting ribs during physical examinations. This can be relevant in medical procedures involving the chest.
- Sternal Cleft: This occurs when the sternum doesn’t completely fuse during development, leaving a gap or split. A sternal cleft can be significant because it may leave the heart and major blood vessels unprotected.
- Sternal Foramen: Similar to a cleft, a sternal foramen is a hole in the sternum resulting from incomplete fusion. This hole is typically oval-shaped.
- Pectus Excavatum (Funnel Chest): In this condition, the sternum and rib cartilage are abnormally indented inwards, giving the chest a sunken appearance.
- Pectus Carinatum (Pigeon Chest): Conversely, pectus carinatum is characterized by an outward protrusion of the sternum and rib cartilage, causing the chest to bulge outwards.
These variations are important for healthcare providers to be aware of, as they can sometimes complicate chest procedures or even be mistaken for fractures on X-rays.
What Does the Sternum Do? Key Functions
The sternum is not just a bone; it performs several critical functions in your body:
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Protection of Vital Organs: The primary function of the sternum is to protect the thoracic mediastinum, the central compartment of the chest. This area houses vital organs including the heart, lungs, thymus gland, lymph nodes, parts of the aorta, trachea (windpipe), esophagus, and key nerves. The sternum acts as a robust shield against external trauma to these delicate organs.
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Muscle Attachment: As mentioned earlier, the sternum provides attachment points for various muscles essential for breathing, neck movement, and abdominal support. The diaphragm’s attachment to the xiphoid process is particularly crucial for respiration.
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Support for Breathing: Through its connection to the ribs via costal cartilage, the sternum plays a vital role in the mechanics of breathing. The flexibility of the costal cartilage allows the chest wall to expand during inhalation and contract during exhalation.
Associated Conditions and Sternum Health
Like any bone, the sternum can be affected by injuries and diseases. Given its protective role over vital organs, sternum-related conditions can sometimes be serious.
Common conditions associated with the sternum include:
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Sternal Fractures: Breaks in the sternum are often caused by high-impact trauma, such as car accidents or direct blows to the chest. Chest compressions during CPR can also, less commonly, cause sternal fractures. Sternal fractures are concerning due to the risk of damage to underlying organs and tissues.
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Costochondritis: This condition involves inflammation of the costal cartilage that connects the ribs to the sternum. Costochondritis causes chest pain, often described as sharp or aching, and tenderness to the touch around the sternum. While the exact cause is often unknown, it can be triggered by injury, heavy lifting, viral infections, or certain types of arthritis.
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Paget’s Disease of Bone (PDB): This chronic bone disorder disrupts the normal process of bone remodeling (breakdown and rebuilding). In PDB, bones become enlarged and weakened. While it can affect any bone, it can involve the sternum. Many people with Paget’s disease have no symptoms, but some experience bone pain and fractures.
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Cancer: Primary cancer originating in the sternum is rare. However, cancer can spread (metastasize) to the sternum from other parts of the body. Chondrosarcoma, a cancer of cartilage, is the most common type of cancer to affect the sternum, often presenting as a slow-growing mass in the chest wall.
Diagnostic Testing for Sternum Problems
When investigating sternum issues, healthcare providers typically start with a medical history and physical examination. If further investigation is needed, they may order various diagnostic tests:
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X-rays: Often the initial imaging test for suspected sternal injuries, particularly fractures. While good for detecting fractures, X-rays are less effective for visualizing soft tissues or tumors in the sternum as they can be obscured by other structures.
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Computed Tomography (CT) Scan: CT scans are the preferred method for detailed imaging of the sternum, especially for detecting lesions like tumors. CT scans provide cross-sectional images, offering better detail than X-rays and are valuable for surgical planning and monitoring cancer growth. CT scans are also helpful in assessing damage to surrounding tissues after a sternal fracture.
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Magnetic Resonance Imaging (MRI): MRI excels at visualizing soft tissues and can be more sensitive than CT scans in detecting cancer spread. MRI is useful when other tests are inconclusive or to evaluate the extent of soft tissue involvement.
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Ultrasound: Ultrasound can be used to detect sternal fractures. While operator-dependent and potentially taking longer to achieve a definitive diagnosis, it’s a radiation-free imaging option.
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Cardiac Monitoring (ECG): Electrocardiograms (ECGs) are essential when sternal injury is suspected, especially after trauma. ECGs monitor heart rhythm and can detect signs of heart bruising or other cardiac complications.
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Blood Tests: Blood tests can provide supportive diagnostic information. Cardiac enzyme levels can help assess heart injury. Alkaline phosphatase (ALP) blood tests can be used to screen for bone disorders like Paget’s disease.
Tips for Keeping Your Sternum Healthy
Maintaining overall bone health is vital for a healthy sternum. Here are some general tips:
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Consume a Calcium and Vitamin D Rich Diet: These nutrients are essential for bone strength. Include dairy products, leafy green vegetables, fortified foods, and consider vitamin D supplementation, especially if you have limited sun exposure.
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Engage in Weight-Bearing Exercise: Activities like walking, running, and weightlifting help strengthen bones, including your sternum.
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Avoid Smoking and Excessive Alcohol: These habits can negatively impact bone density.
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Practice Good Posture: Proper posture can help maintain the alignment and health of your entire skeletal system, including your sternum and rib cage.
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Protect Yourself from Injury: Wear seatbelts in vehicles and appropriate protective gear during sports and activities that carry a risk of chest trauma.
In Summary: Your Sternum and You
Where is your sternum? It’s centrally located in your chest, right in the middle of your rib cage. This bone, often called the breastbone, is a critical protector of your heart and lungs, supports breathing, and anchors key muscles. While variations in sternum shape are common and usually harmless, conditions and injuries affecting the sternum can have significant health implications. Taking care of your bone health through diet, exercise, and injury prevention is vital for ensuring your sternum can continue to perform its essential roles throughout your life. Understanding your sternum is a key step in taking proactive care of your overall health and well-being.
