The sternal angle, also known as the angle of Louis, is the prominent ridge formed at the junction between the manubrium and the body of the sternum.
In-Depth Explanation:
The sternal angle is a crucial anatomical landmark that can be easily palpated (felt) on the anterior chest wall. It marks the location of the manubriosternal joint, where the manubrium (the upper portion of the sternum) articulates with the body of the sternum (the larger, central portion). This joint is a symphysis, meaning it is a slightly movable cartilaginous joint.
Significance of the Sternal Angle:
The sternal angle serves as an important reference point for several anatomical structures:
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Second Rib: It is located approximately at the level of the second rib. Therefore, it helps in counting ribs for auscultation (listening to) of the heart and lungs.
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T4 Vertebra: Internally, it corresponds to the level of the intervertebral disc between the T4 and T5 vertebrae.
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Bifurcation of the Trachea: The trachea (windpipe) divides into the left and right main bronchi at approximately the level of the sternal angle.
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Beginning and End of the Aortic Arch: The aortic arch begins and ends roughly at this level.
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Superior Mediastinum: The sternal angle separates the superior and inferior mediastinum (the central compartment of the thoracic cavity).
Clinical Relevance:
Because of its easily palpable location and its relation to vital anatomical structures, the sternal angle is an essential landmark in physical examinations, diagnostic procedures, and surgical planning.
In summary, the sternal angle is a key anatomical landmark on the anterior chest that helps healthcare professionals locate and identify other underlying structures.
