The sternum, also known as the breastbone, is a vital bone in the center of your chest. Are you looking for comprehensive information about the sternum? WHAT.EDU.VN provides clear and accessible answers to all your questions about sternum anatomy, function, and related clinical conditions. Learn about sternal variations, surgical considerations, and forensic implications with our detailed explanations.
1. What Is a Sternum and What Is Its Primary Function?
The sternum, or breastbone, is a flat, T-shaped bone located in the center of the chest that connects the ribs to protect the heart, lungs, and major blood vessels. Its primary function is to shield these vital organs from injury.
The sternum is crucial for protecting the mediastinum, the central compartment of the thoracic cavity containing the heart, lungs, trachea, and esophagus. Understanding the sternum’s anatomy is vital in various medical fields, including surgery, forensic science, and general healthcare.
2. What Are the Three Main Parts of the Sternum?
The sternum consists of three main parts: the manubrium, the body, and the xiphoid process.
- Manubrium: The manubrium is the broad, upper section of the sternum. It features the suprasternal notch (jugular notch) at the top and clavicular notches on either side, where it articulates with the clavicles to form the sternoclavicular joints. It also connects to the first pair of ribs via costal cartilages.
- Body: The body, or mesosternum, is the longest part of the sternum. It’s flat with ridges along the sides where the costal cartilages of the third to seventh pairs of ribs articulate. The sternal angle, where the body joins the manubrium, is an important anatomical landmark for locating the second rib.
- Xiphoid Process: The xiphoid process, or xiphisternum, is a small, triangular-shaped piece of cartilage at the bottom of the sternum. It varies greatly in size and shape and gradually ossifies with age, becoming fully calcified around age 60.
3. Where Is the Sternal Angle and Why Is It Important?
The sternal angle, also known as the Angle of Louis, is the junction between the manubrium and the body of the sternum. It’s an important anatomical landmark because it corresponds to the level of the second rib’s costal cartilage attachment.
The sternal angle is a palpable projection that can be used to count the ribs during physical examinations. This is crucial for accurately identifying and locating various thoracic structures.
4. How Does the Sternum Develop During Embryonic Development?
The sternum develops during the 6th week of fetal life from two sternal bands composed of mesenchymal cells. By the 10th week, these bands convert into pre-cartilaginous structures that migrate and fuse in a craniocaudal direction to form the sternal plate.
During the 7th week, the mesenchyme condenses to form the primary cartilaginous model of the sternum, consisting of six horizontal divisions known as sternebrae. The uppermost and lowermost sternebrae become the manubrium and xiphoid process, respectively, while the four in between form the body of the sternum.
5. What Is the Blood Supply to the Sternum?
The sternum’s blood supply primarily comes from the medial horizontal branches of the right and left internal thoracic arteries, which originate from the subclavian arteries. These arteries give off sternal, anterior intercostal, perforating, and non-collateral branches.
The sternal branches are mainly located in the intercostal spaces and play a vital role in bone healing, especially after sternotomy procedures. Understanding the blood supply is also important in preventing sternal infections following internal thoracic artery harvesting for coronary artery bypass grafting.
6. What Muscles Attach to the Sternum?
Several muscles attach to the sternum, including muscles of the neck, thorax, and anterior abdominal wall.
- Manubrium: The sternocleidomastoid, sternohyoid, and sternothyroid muscles attach to the manubrium.
- Body: The transversus thoracis and pectoralis major muscles attach to the body of the sternum.
- Xiphoid Process: The xiphoid process provides an attachment site for the diaphragm and abdominal muscles like the external oblique, internal oblique, transversus abdominis, and rectus abdominis.
7. What Are Some Common Anatomic Variations of the Sternum?
Common anatomic variations of the sternum include a shorter and thinner body in females compared to males, and variations in the xiphoid process, such as a bifid (split) xiphoid.
Other variations include misplaced sternal angles, which can lead to inaccurate rib counting and procedural errors. Sternal clefts, resulting from the failure of midline fusion, and sternal foramina, caused by incomplete fusion of the cartilaginous sternal model, are also notable variations.
8. What Is a Sternal Cleft and Why Is It Clinically Significant?
A sternal cleft is a congenital defect resulting from the failure of the sternum to fuse properly during development. It leaves the heart and great vessels exposed and unprotected.
Sternal clefts can be complete or incomplete, depending on the degree of separation. Narrow clefts can be mistaken for sternal fractures, making accurate diagnosis crucial.
9. What Is a Sternal Foramen and Why Is It Important to Recognize?
A sternal foramen is a hole in the sternum resulting from incomplete fusion of the cartilaginous sternal model. It’s important to recognize because it can be mistaken for an abnormality during imaging studies of the thorax.
Radiologists, surgeons, and forensic pathologists should be aware of sternal foramina to avoid misdiagnosis or misinterpretation during examinations.
10. What Is a Median Sternotomy and Why Is It Performed?
A median sternotomy is a surgical incision where the sternum is split along the median plane to access the heart, great vessels, and lungs. It’s considered the benchmark incision for cardiac surgery.
Median sternotomies provide surgeons with a better view of the thoracic cavity, making it the most common osteotomy performed worldwide.
11. What Are Sternal Aspiration and Sternal Biopsy and Why Are They Performed?
Sternal aspiration and sternal biopsy are procedures to collect bone marrow samples from the sternum. The sternum is a preferred site because hematopoietic marrow persists there throughout life.
These procedures are indicated for diagnosing blood dyscrasias and metastatic cancer.
12. How Can the Sternum Be Used in Forensic Science?
In forensic science, the sternum can be examined to help establish a person’s identity. Forensic pathologists and osteologists use the sternum to estimate sex, age, and stature from skeletal remains.
Studies on sternal measurements and characteristics are population-specific, and forensic anthropological studies are conducted worldwide to improve the accuracy of these estimations.
13. How Are Sternal Fractures Usually Caused?
Sternal fractures are typically caused by significant blunt trauma to the chest, such as from motor vehicle accidents, falls, or direct blows.
They can also result from iatrogenic causes, like improper CPR techniques.
14. What Are the Symptoms of a Sternal Fracture?
Symptoms of a sternal fracture include:
- Chest pain, especially with deep breathing or coughing
- Tenderness over the sternum
- Bruising or swelling around the sternum
- Difficulty breathing
15. How Are Sternal Fractures Diagnosed?
Sternal fractures are usually diagnosed with imaging tests such as:
- X-rays: To visualize the fracture
- CT scans: To provide a more detailed view of the sternum and surrounding structures
16. What Are the Treatment Options for Sternal Fractures?
Treatment options for sternal fractures depend on the severity and stability of the fracture.
- Non-surgical treatment: Includes pain management with analgesics and rest.
- Surgical fixation: May be necessary for displaced or unstable fractures, using locked titanium plates and depth-limited drilling.
17. What Are the Potential Complications of Sternal Fractures?
Potential complications of sternal fractures include:
- Pain
- Difficulty breathing
- Pneumothorax (collapsed lung)
- Cardiac contusion
- Infection
18. Can CPR Cause a Sternal Fracture?
Yes, CPR (cardiopulmonary resuscitation) can cause a sternal fracture, especially if performed incorrectly. The risk of fracture increases in elderly individuals and those with osteoporosis.
19. What Are the Forensic Implications of Sternal Bone Marrow Aspiration Fatalities?
Fatalities related to sternal bone marrow aspiration are considered medicolegal deaths and require thorough investigation. These cases often involve accidental penetrating injuries to major blood vessels.
Ultrasound-guided sternal bone marrow aspiration is recommended to minimize the risk of such incidents.
20. What Are the Recent Advances in Understanding Sternum Anatomy and Function?
Recent advances include improved imaging techniques for diagnosing sternal fractures and variations, as well as enhanced surgical methods for sternal fixation.
Ongoing research focuses on refining forensic techniques for age, sex, and stature estimation from the sternum.
21. What Is Pectus Excavatum and How Is It Related to the Sternum?
Pectus excavatum, also known as funnel chest, is a congenital chest wall deformity characterized by a sunken or caved-in sternum. This condition can range from mild to severe, potentially compressing the heart and lungs in severe cases.
Pectus excavatum occurs due to abnormal growth of the costal cartilages, causing the sternum to be pushed inward.
22. What Is Pectus Carinatum and How Does It Differ From Pectus Excavatum?
Pectus carinatum, also known as pigeon chest, is another chest wall deformity where the sternum protrudes outward. Unlike pectus excavatum, pectus carinatum results in a forward projection of the sternum and ribs.
Both conditions are congenital but differ in the direction of sternal displacement.
23. How Is Sex Determined From the Sternum in Forensic Analysis?
Sex determination from the sternum involves morphometric analysis, measuring various dimensions of the sternum to identify sexual dimorphism. Females typically have a shorter and thinner sternal body compared to males.
Researchers have developed sternal indices and discriminant functions based on sternal measurements to improve the accuracy of sex estimation in forensic contexts.
24. How Is Age Estimated Using the Sternum in Forensic Science?
Age estimation using the sternum is based on the progressive ossification of the sternal segments and the fusion of the manubrium, body, and xiphoid process. These changes occur at different rates and ages, providing a basis for age estimation.
Forensic anthropologists analyze the sternal surface and bone structure to estimate the age of skeletal remains.
25. How Is Stature Estimated From the Sternum in Forensic Anthropology?
Stature estimation from the sternum involves measuring the length of the sternum and using regression formulas derived from specific populations. Studies have shown a positive correlation between sternal length and overall stature.
These formulas vary depending on sex and population, so population-specific data is crucial for accurate stature estimation.
26. What Are the Challenges in Forensic Analysis of the Sternum?
Challenges in forensic analysis of the sternum include:
- Variations: Anatomic variations can complicate sex and age estimation.
- Population specificity: Formulas for stature estimation are population-specific.
- Degradation: Postmortem changes and skeletal fragmentation can affect the accuracy of measurements.
27. What Role Does the Sternum Play in Breathing?
The sternum plays an indirect role in breathing by providing attachment points for muscles involved in respiration, such as the diaphragm and intercostal muscles.
The sternum’s stability and position are essential for the proper function of these muscles, allowing for efficient chest expansion and contraction during breathing.
28. How Does the Sternum Contribute to Posture?
The sternum contributes to posture by supporting the rib cage and providing a stable base for the muscles of the chest and abdomen.
Its position and alignment influence the overall curvature of the spine and the distribution of weight in the upper body.
29. What Are the Differences Between Male and Female Sternums?
Key differences between male and female sternums include:
- Size: Females generally have shorter and thinner sternums compared to males.
- Shape: The manubrium may be proportionally larger in females.
- Robusticity: Male sternums tend to be more robust and have more pronounced muscle attachments.
30. How Does Osteoporosis Affect the Sternum?
Osteoporosis can weaken the sternum, making it more susceptible to fractures, especially during CPR or blunt trauma.
The decreased bone density associated with osteoporosis reduces the sternum’s ability to withstand mechanical stress.
31. What Are the Ethical Considerations in Forensic Analysis of the Sternum?
Ethical considerations in forensic analysis of the sternum include:
- Respect for human remains: Handling skeletal remains with dignity and respect.
- Accuracy and reliability: Ensuring the accuracy and reliability of forensic estimations.
- Privacy and confidentiality: Protecting the privacy of the deceased and their families.
32. What Is the Relationship Between the Sternum and Ribs?
The sternum and ribs are connected by costal cartilages, forming the anterior rib cage. The costal cartilages provide flexibility and allow the rib cage to expand and contract during breathing.
This connection is essential for protecting the thoracic organs and facilitating respiratory movements.
33. What Are the Latest Technologies Used to Study the Sternum?
Latest technologies used to study the sternum include:
- Multislice computed tomography (MSCT): Provides detailed 3D images of the sternum.
- 3D printing: Allows for the creation of anatomical models for surgical planning and education.
- Finite element analysis: Simulates the biomechanical behavior of the sternum under different loading conditions.
34. What Are the Psychological Effects of Sternal Deformities?
Psychological effects of sternal deformities like pectus excavatum and pectus carinatum can include:
- Body image issues: Feeling self-conscious about the appearance of the chest.
- Social anxiety: Avoiding social situations due to embarrassment.
- Depression: Experiencing feelings of sadness and hopelessness.
35. How Do Sternal Deformities Impact Quality of Life?
Sternal deformities can impact quality of life by causing:
- Physical limitations: Difficulty with exercise and physical activities.
- Respiratory problems: Reduced lung capacity and shortness of breath.
- Cardiovascular issues: Compression of the heart in severe cases.
- Psychological distress: Negative impact on self-esteem and mental well-being.
36. What Surgical Techniques Are Used to Correct Sternal Deformities?
Surgical techniques used to correct sternal deformities include:
- Nuss procedure: Minimally invasive procedure for pectus excavatum, using a curved metal bar to push the sternum forward.
- Ravitch procedure: Open surgical technique for both pectus excavatum and pectus carinatum, involving reshaping or removing the abnormal cartilage.
37. How Can Exercise Help With Sternal Deformities?
Exercise can help with sternal deformities by:
- Improving posture: Strengthening muscles that support the chest and spine.
- Increasing lung capacity: Enhancing respiratory function.
- Boosting self-esteem: Promoting a positive body image through physical activity.
38. What Are the Non-Surgical Treatments for Sternal Deformities?
Non-surgical treatments for sternal deformities include:
- Bracing: Wearing a custom-fitted brace to gradually reshape the chest wall.
- Vacuum bell therapy: Using a suction device to lift the sternum forward in pectus excavatum.
- Physical therapy: Exercises to improve posture and strengthen chest muscles.
39. How Is Pain Managed After Sternal Fracture Surgery?
Pain management after sternal fracture surgery typically involves:
- Analgesics: Pain medications, including opioids and non-opioid pain relievers.
- Nerve blocks: Injections to numb the nerves in the chest wall.
- Physical therapy: Exercises to restore range of motion and reduce pain.
40. What Are the Long-Term Outcomes After Sternal Fracture Repair?
Long-term outcomes after sternal fracture repair can include:
- Pain relief: Reduced pain and discomfort in the chest.
- Improved function: Increased ability to perform physical activities.
- Cosmetic improvement: Enhanced appearance of the chest.
- Return to normal life: Resuming regular activities and hobbies.
41. How Does Age Affect Sternal Fracture Healing?
Age can affect sternal fracture healing by:
- Slower healing: Older individuals may experience slower bone healing due to decreased bone density and reduced blood supply.
- Increased complications: Elderly patients are at higher risk of complications such as infection and non-union.
42. What Is the Role of Nutrition in Sternal Fracture Healing?
Nutrition plays a crucial role in sternal fracture healing by:
- Providing essential nutrients: Calcium, vitamin D, and protein are necessary for bone repair and regeneration.
- Supporting immune function: Adequate nutrition helps prevent infection and promote healing.
- Reducing inflammation: Certain nutrients can help reduce inflammation and pain.
43. What Is the Recovery Time After Sternal Fracture?
The recovery time after a sternal fracture varies depending on the severity of the fracture and the treatment approach.
- Non-surgical treatment: Recovery may take 6-8 weeks.
- Surgical fixation: Recovery may take 3-6 months.
44. What Are the Risks of Sternal Bone Marrow Aspiration?
Risks of sternal bone marrow aspiration include:
- Bleeding: Excessive bleeding at the aspiration site.
- Infection: Introduction of bacteria into the bone marrow.
- Injury to nearby structures: Puncture of the heart, lungs, or major blood vessels.
45. How Can the Risks of Sternal Bone Marrow Aspiration Be Minimized?
The risks of sternal bone marrow aspiration can be minimized by:
- Using ultrasound guidance: Visualizing the sternum and surrounding structures during the procedure.
- Employing proper technique: Following established protocols and guidelines.
- Taking necessary precautions: Screening patients for bleeding disorders and using appropriate sterile techniques.
46. What Research Is Being Conducted on the Sternum?
Ongoing research on the sternum includes:
- Forensic analysis: Developing more accurate methods for age, sex, and stature estimation.
- Surgical techniques: Improving surgical approaches for sternal fracture repair and sternal deformity correction.
- Biomaterials: Investigating new materials for sternal fixation and reconstruction.
47. How Can Telemedicine Be Used in the Management of Sternal Conditions?
Telemedicine can be used in the management of sternal conditions by:
- Providing remote consultations: Allowing patients to discuss their symptoms and concerns with healthcare providers from home.
- Monitoring recovery: Tracking progress and providing guidance on pain management and rehabilitation.
- Facilitating access to specialists: Connecting patients with experts in sternal conditions, regardless of their location.
48. What Are the Support Resources Available for People With Sternal Conditions?
Support resources available for people with sternal conditions include:
- Online support groups: Connecting with others who have similar conditions.
- Patient advocacy organizations: Providing information, resources, and support.
- Mental health professionals: Offering counseling and therapy to address psychological effects.
49. What Questions Should I Ask My Doctor About My Sternum Health?
Questions to ask your doctor about your sternum health include:
- What are the risk factors for sternal fractures or deformities?
- What can I do to maintain my sternum health?
- What are the treatment options for my specific condition?
- What are the potential risks and benefits of each treatment?
- What is the recovery process like?
50. How Can I Learn More About Sternal Anatomy and Function?
To learn more about sternal anatomy and function, consider the following resources:
- Medical textbooks: Comprehensive information on anatomy and physiology.
- Anatomy websites: Online resources with detailed illustrations and explanations.
- Educational videos: Visual aids for understanding complex concepts.
Remember, if you have any questions about your health, it’s always best to consult with a healthcare professional.
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