The sternum may seem like a simple bone, but it plays a crucial role in protecting vital organs and supporting the mechanics of breathing. Located at the center of the chest, it forms the front portion of the ribcage and serves as an important anatomical landmark in both assessment and emergency care.
For respiratory therapists, understanding the sternum is more than basic anatomy; it directly connects to patient evaluation, chest movement, airway management, and life-saving interventions such as CPR.
This article explores what the sternum is, how it functions, and why it holds significant importance in the field of respiratory care.
What is the Sternum?
The sternum, or breastbone, is a flat, elongated bone located in the center of the chest that forms the front portion of the ribcage. It connects with the clavicles and the first seven pairs of ribs, creating a strong protective shield for vital organs such as the heart, lungs, and major blood vessels.
Structurally, the sternum is made up of three parts: the manubrium at the top, the body in the middle, and the xiphoid process at the bottom. Beyond protection, the sternum plays an important role in breathing because it serves as a central anchor for the ribs, allowing the chest to expand during inhalation.
For healthcare providers and respiratory therapists, it also serves as a key anatomical landmark used during physical assessments, CPR, and airway management. Understanding the sternum’s structure and function is essential in evaluating and supporting a patient’s respiratory status.
Parts of the Sternum
The sternum consists of the following parts:
- Manubrium: The upper portion of the sternum. It articulates with the clavicles (collar bones) and the first two ribs, forming the major joints of the shoulders and the front of the rib cage.
- Body (Gladiolus): This is the longest part of the sternum. It connects to the manubrium above and the xiphoid process below. The body provides attachment points for most of the ribs through costal cartilage.
- Xiphoid Process: The smallest and most variable part, the xiphoid process is a thin, elongated structure that projects downward. It is made of cartilage in young individuals but gradually ossifies (turns into bone) with age. It serves as an attachment site for various muscles and ligaments.
Function
The sternum serves several key functions:
- Protection of Vital Organs: It forms a protective shield for the heart, lungs, and major blood vessels, guarding them against physical impacts.
- Support and Structure: As a central part of the rib cage, the sternum provides structural support for the upper body and aids in maintaining the shape and integrity of the chest cavity.
- Muscle Attachment: Various muscles, including those used in breathing (like the diaphragm) and major upper body muscles, attach to the sternum, facilitating movement and respiratory functions.
- Assisting in Respiration: By being a part of the rib cage, it helps in the expansion and contraction of the chest during breathing.
Development of the Sternum
The development of the sternum begins in the embryonic stage as bilateral strips of cartilaginous tissue in the thoracic region. These strips, known as sternal bars, gradually fuse together down the midline to form a single cartilaginous model of the sternum.
This fusion typically occurs during the sixth to ninth weeks of embryonic development. As the fetus grows, the cartilaginous model begins to ossify from several ossification centers.
The process starts in the manubrium and the body (gladiolus) of the sternum during late fetal development or soon after birth. The xiphoid process, being the last to ossify, may remain cartilaginous well into adulthood. This ossification process is usually complete by the age of 25, resulting in a fully developed and hardened sternum, essential for its protective and structural roles in the human body.
Why the Sternum Matters in Respiratory Care
Respiratory therapists interact with patients whose breathing mechanics, chest movement, and thoracic stability are often compromised. Understanding the sternum is essential because:
1. It Protects Vital Respiratory Structures
The sternum shields the heart, major vessels, and portions of the lungs from external injury. Trauma to the chest often involves the sternum and can impair ventilation or circulation.
2. It Plays a Role in Breathing Mechanics
During inspiration, the ribs elevate and expand outward in a “pump-handle” motion. This motion depends partly on the sternum acting as a stable central hinge. Any condition that limits sternal mobility, such as pain, deformity, or surgery, can reduce thoracic expansion and compromise ventilation.
3. It Influences Respiratory Assessment
RTs frequently assess:
- Chest rise and symmetry – asymmetry may indicate pneumothorax, atelectasis, or obstruction
- Use of accessory muscles – noticeable retractions along the sternum may signal increased work of breathing, especially in pediatric patients
- Tenderness or instability – a fractured sternum or sternal clicks can accompany trauma or surgical healing complications
Note: A clear understanding of normal sternal anatomy helps clinicians recognize abnormalities quickly.
4. It Serves as a Key Landmark
The sternum contains several important reference points:
- Sternal angle (Angle of Louis) at the manubriosternal junction marks the level of rib 2 and the bifurcation of the trachea
- Xiphoid process is used as a landmark during CPR, abdominal thrusts, and positioning for certain procedures
Note: For respiratory therapists, the sternal angle is particularly useful when correlating auscultation sites, identifying lobar locations, and locating structures during assessments.
5. It Has Clinical Relevance After Surgery
Patients recovering from open-heart or thoracic surgery often have a sternotomy incision. RTs are deeply involved in:
- Teaching splinting techniques during coughing
- Providing airway clearance therapy
- Monitoring for signs of sternal separation
- Promoting lung expansion exercises such as IS (Incentive Spirometry)
Note: Proper management reduces complications like pneumonia and atelectasis.
Conditions Affecting the Sternum That Impact Breathing
Respiratory therapists may encounter patients with:
- Sternal fractures from trauma
- Costochondritis causing chest wall pain
- Pectus excavatum or carinatum altering thoracic shape and lung volumes
- Post-operative sternal instability following cardiac surgery
Note: These conditions can interfere with chest movement, cause pain-induced hypoventilation, and contribute to impaired gas exchange or ineffective cough.
Pectus Excavatum vs. Pectus Carinatum
Pectus excavatum and pectus carinatum are two different types of congenital deformities of the chest wall, involving the sternum and the ribs.
- Pectus Excavatum: Often referred to as “funnel chest,” pectus excavatum is characterized by a sunken appearance of the chest. In this condition, the sternum and adjacent cartilages are depressed inward towards the spine, creating a concave shape in the chest. This can be mild or severe and may cause issues with the heart and lungs in more pronounced cases, as well as psychological distress due to the chest’s appearance.
- Pectus Carinatum: Commonly known as “pigeon chest,” pectus carinatum is the opposite of pectus excavatum. It features a protrusion of the sternum and the ribs outward, giving the chest a convex or bulging appearance. This condition is less likely to cause physical complications compared to pectus excavatum, but it can still lead to self-consciousness about body image.
Both conditions are generally present at birth, but they often become more noticeable during the adolescent growth spurt.
While the exact cause of these deformities is not completely understood, they are believed to result from abnormal growth of the cartilage that connects the ribs to the sternum. Treatment options vary based on severity and can range from physical therapy and braces to surgical correction.
Sternum Practice Questions
1. What is the sternum, and where is it located?
A flat, elongated bone in the center of the chest forming the anterior portion of the rib cage.
2. Which structures articulate directly with the sternum?
The clavicles and the first seven pairs of ribs via costal cartilage.
3. What are the three anatomical parts of the sternum?
Manubrium, body (gladiolus), and xiphoid process.
4. What is the function of the manubrium?
It articulates with the clavicles and upper ribs, forming the superior portion of the sternum.
5. Which sternum section is the longest?
The body (gladiolus).
6. What is significant about the xiphoid process in young individuals?
It is cartilaginous and later ossifies with age.
7. Why is the sternum important for respiration?
It anchors the ribs and allows thoracic expansion during inhalation.
8. Which vital organs are protected by the sternum?
The heart, lungs, and major blood vessels.
9. What anatomical landmark marks the transition between the manubrium and the body of the sternum?
The sternal angle (Angle of Louis).
10. The sternal angle is located at the same level as which internal structure?
The tracheal bifurcation (carina).
11. Why is the sternal angle important during respiratory assessment?
It helps identify rib locations and lung fields for auscultation.
12. What movement of the sternum occurs during inspiration?
A “pump-handle” elevation that increases the anterior–posterior diameter of the thorax.
13. Why is sternal mobility important?
Reduced mobility can impair chest expansion and ventilation.
14. What is a common cause of pain-induced hypoventilation related to the sternum?
Sternal fractures or costochondral inflammation.
15. How does pectus excavatum affect breathing mechanics?
It depresses the sternum inward, potentially reducing lung volumes and impairing ventilation.
16. What is the primary feature of pectus carinatum?
Protrusion of the sternum outward (pigeon chest).
17. What developmental structures form the sternum in early embryology?
Two sternal bars that fuse at the midline.
18. At what approximate age is sternal ossification complete?
Around age 25.
19. Why must the xiphoid process be avoided during CPR?
Pressure over it can cause trauma to the liver or abdominal organs.
20. What landmark is used to determine correct hand placement during adult CPR?
The lower half of the sternum, just above the xiphoid process.
21. During CPR, what is the purpose of depressing the sternum?
To generate forward blood flow by compressing the heart between the sternum and spine.
22. What clinical sign may suggest sternal instability after surgery?
A palpable clicking or movement of the sternum during breathing or coughing.
23. Why are respiratory therapists concerned with sternal precautions post-sternotomy?
Excessive movement can impair healing and reduce the patient’s ability to cough effectively.
24. What condition involving the sternum can occur following severe blunt trauma?
Sternal fracture.
25. Why might a sternal fracture impair ventilation?
Pain limits deep breaths, increasing the risk of atelectasis.
26. What respiratory assessment finding may accompany costochondritis?
Localized chest wall tenderness without lung abnormalities.
27. What muscle attaches to the xiphoid process and contributes to breathing?
The diaphragm.
28. What does asymmetrical chest rise near the sternum indicate?
Possible pneumothorax, obstruction, or poor lung expansion on one side.
29. Why is the sternum a useful landmark during tracheal intubation?
It helps evaluate chest rise, tube depth, and proper ventilation.
30. What sternal finding in infants suggests increased work of breathing?
Suprasternal retractions during inspiration.
31. Which rib attaches directly at the level of the sternal angle (Angle of Louis)?
The second rib.
32. What effect does severe chest wall pain near the sternum have on ventilation?
It decreases tidal volume due to shallow breathing.
33. What finding may occur when the sternum fails to fuse properly during development?
Sternal cleft or pectus deformity.
34. Which motion does the sternum contribute to during quiet inspiration?
Anterior and superior elevation.
35. What respiratory consequence can occur after median sternotomy?
Reduced chest wall compliance.
36. Why is assessing sternal tenderness important in trauma patients?
It may indicate underlying pulmonary injury such as contusion.
37. What condition is suggested when the sternum shifts inward during inhalation?
Significant upper airway obstruction or severe retractions.
38. What thoracic structure lies directly posterior to the manubrium?
The great vessels, including the aortic arch.
39. Which airway management complication can present as substernal crepitus?
Subcutaneous emphysema due to barotrauma.
40. What sternal structure identifies the approximate location of the carina ?
The sternal angle.
41. Why is the sternum important when assessing chest symmetry?
Its midline position helps compare right and left thoracic movement.
42. What does pain over the costosternal junction suggest?
Costochondritis or inflammation of the cartilage.
43. What factor reduces sternal expansion in restrictive lung disease?
Decreased chest wall compliance.
44. What finding near the sternum may indicate impending respiratory failure in infants?
Marked suprasternal retractions.
45. How can a sternal fracture compromise ventilation?
Pain inhibits deep breaths, leading to atelectasis.
46. What respiratory change occurs if the sternum becomes unstable after surgery?
Paradoxical chest wall movement.
47. Why is the xiphoid process avoided during manual ventilation maneuvers?
Pressure on it risks internal organ injury.
48. What clinical indicator suggests sternal instability after thoracic surgery?
A noticeable “click” during breathing or coughing.
49. Which maneuver positions the sternum to align airway axes during intubation?
The sniffing position.
50. What anatomical relationship helps determine tube depth during intubation?
Distance from incisors to sternal notch when observing chest rise.
51. What does limited sternal elevation during inhalation indicate?
Reduced thoracic mobility or restrictive impairment.
52. Why is the sternum assessed during airway obstruction evaluations?
Retractions above it indicate increased negative intrathoracic pressure.
53. Which structure attaches to the posterior surface of the xiphoid process?
The central tendon of the diaphragm.
54. How does pectus excavatum affect cardiac and pulmonary function?
It reduces anterior thoracic space, limiting lung expansion.
55. What visible finding at the sternum indicates severe work of breathing?
Suprasternal tugging or retractions.
56. What chest wall abnormality is characterized by outward displacement of the sternum?
Pectus carinatum.
57. What landmark is used to differentiate upper from lower lung fields during auscultation?
The sternal angle.
58. Why is the sternum important during noninvasive ventilation assessments?
Movement and stability indicate patient effort and chest wall compliance.
59. What does bruising directly over the sternum suggest in a trauma patient?
Possible cardiac or pulmonary contusion beneath the impact site.
60. How does sternal rigidity influence lung inflation during mechanical ventilation?
A rigid sternum supports efficient chest wall expansion under positive pressure.
61. What does marked tenderness along the sternum suggest in a patient receiving CPR?
Possible sternal fracture from chest compressions.
62. Why must sternal movement be observed when evaluating spontaneous breathing?
It reflects the effectiveness of thoracic expansion.
63. What respiratory complication may develop when sternal pain prevents deep inhalation?
Atelectasis due to shallow breathing.
64. What does inward movement of the sternum during inspiration indicate in infants?
Severe airway obstruction or increased work of breathing.
65. How does pectus excavatum alter lung function?
It restricts anterior chest expansion and may reduce lung volumes.
66. What does the sternum protect that is vital to oxygenation and circulation?
The heart and great vessels.
67. Why is the sternal angle useful when placing stethoscope landmarks?
It identifies the second intercostal space and helps locate lung lobes.
68. What clinical sign near the sternum suggests hyperinflation in obstructive lung disease?
Prominent chest elevation with limited downward movement.
69. Why is sternal stability assessed after thoracic surgery?
Instability can impair breathing mechanics and increase infection risk.
70. What does suprasternal retraction typically indicate?
Upper airway obstruction or increased inspiratory effort.
71. How might sternal pressure influence preoxygenation during airway preparation?
Pain or instability limits deep breaths and reduces alveolar filling.
72. What finding along the sternum suggests subcutaneous air from barotrauma?
Palpable crepitus.
73. Why is the sternum a key landmark during manual ventilation?
Chest rise over the sternum confirms adequate tidal volume delivery.
74. What physical change in the sternum may occur in patients with chronic lung hyperinflation?
Increased anterior-posterior chest diameter.
75. Why is the xiphoid process avoided during abdominal thrusts?
Pressure there may damage internal organs like the liver.
76. What sternal feature helps clinicians identify tracheal bifurcation levels externally?
The sternal angle correlates with the carina.
77. What respiratory issue may follow pain from sternal contusion?
Hypoventilation from splinting or shallow breathing.
78. How can the sternum help detect paradoxical breathing?
The sternum moves inward during inspiration while the abdomen rises.
79. Which clinical observation near the sternum suggests severe respiratory muscle fatigue?
Minimal or absent sternal rise during inspiration.
80. What sternal landmark is important when evaluating clavicular fractures?
The manubrium connects directly to the clavicles.
81. How does sternal retraction affect negative intrathoracic pressure generation?
It indicates excessive effort to overcome airway resistance.
82. What condition may cause a visible outward bowing of the sternum?
Pectus carinatum.
83. What sternal abnormality can limit the effectiveness of cough?
Chest wall deformity reducing force generation.
84. Why is the sternum assessed in suspected pneumothorax?
Asymmetric sternal movement may accompany unilateral chest expansion.
85. How can sternal landmarks assist in central line placement?
They help identify midline structures and avoid vascular injury.
86. What respiratory pattern may occur if pain prevents sternal expansion?
Rapid, shallow breathing.
87. What does limited sternal rise in a sedated patient indicate?
Reduced respiratory drive or inadequate ventilation.
88. Which muscles attached to the sternum aid in deep inspiration?
The sternocleidomastoids and pectoralis major.
89. What sternal indicator may suggest fluid buildup in the thorax?
Decreased chest wall movement over the sternum.
90. Why is the sternum important during resuscitation assessment?
It provides the compression point needed to generate forward blood flow.
91. What does pronounced sternal retraction during inspiration typically indicate in children?
Severe airway obstruction or respiratory distress.
92. How does a sternal fracture impact ventilation?
Pain limits chest expansion, leading to hypoventilation and possible atelectasis.
93. Why is the sternum monitored after open-heart surgery?
Sternal dehiscence can impair breathing and increase infection risk.
94. What does minimal chest rise over the sternum during bag-mask ventilation suggest?
Inadequate tidal volume or an ineffective mask seal.
95. How can the sternum help identify poor diaphragm function?
Paradoxical upward movement may occur when diaphragm weakness forces accessory muscle compensation.
96. What finding along the sternum may occur in tension pneumothorax?
Shifted or asymmetric sternal movement from mediastinal deviation.
97. Why is the sternum examined during trauma assessment?
Direct blows can cause fractures that compromise ventilation and circulation.
98. What does persistent sternal pain after coughing indicate?
Possible costochondritis or inflammation of costal cartilage.
99. Why is palpation along the sternum useful when evaluating upper airway obstruction?
Suprasternal retractions quantify the degree of inspiratory effort.
100. How does chest wall rigidity involving the sternum affect mechanical ventilation?
Reduced compliance increases airway pressures and work of breathing.
Final Thoughts
In summary, the sternum is far more than a structural centerpiece of the chest. Its role in protecting vital organs, supporting rib movement during breathing, and serving as a landmark for clinical assessments makes it essential knowledge for anyone in respiratory care.
Whether evaluating chest expansion, assisting post-surgical patients, or performing life-saving interventions, respiratory therapists rely on the sternum as a guide and a functional component of the respiratory system.
Understanding its anatomy and significance helps clinicians provide safer, more effective care and strengthens their ability to recognize and respond to changes in a patient’s respiratory status.
Written by:
John Landry is a registered respiratory therapist from Memphis, TN, and has a bachelor's degree in kinesiology. He enjoys using evidence-based research to help others breathe easier and live a healthier life.
References
- Altalib AA, Miao KH, Menezes RG. Anatomy, Thorax, Sternum. 2023 Jul 24. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2023.