Sternum
The sternum is a flat bone located at the midline of the anterior thorax, composed of three primary sections:
- Manubrium
- Body of the Sternum
- Xiphoid Process
The manubrium is the superior portion of the sternum and features a pair of egg-shaped clavicular facets on either side, which articulate with the clavicles to provide structural stability for the upper limb.
On the lateral edges of the manubrium, the costal facets serve as attachment sites for the first and second ribs, contributing to anterior thoracic cage stability.
At the superior surface of the manubrium, the jugular notch forms a U-shaped depression between the clavicular facets, serving as a notable anatomical landmark.
Osteological Features of the Sternum
- Manubrium – The broad, upper part of the sternum
- Clavicular Facet – Articulating surface for the clavicle
- Costal Facets – Sites of rib attachment
- Jugular Notch – Superior central depression
Clavicle
When viewed from above, the shaft of the clavicle exhibits a distinctive S-shaped curvature, characterized by a medial convexity and lateral concavity. This structure balances shoulder stability and mobility.
In the anatomical position, the long axis of the clavicle is slightly above the horizontal plane and angled approximately 20° posteriorly relative to the frontal plane. This orientation optimizes upper limb function.
The medial end of the clavicle, known as the sternal end, is rounded and prominent, articulating with the sternum to form the sternoclavicular joint, a key structural link between the axial skeleton and upper limb.
The costal facet at the sternal end interfaces with the first rib, providing a stable support structure. Adjacent to this facet, the costal tuberosity serves as the attachment site for the costoclavicular ligament, further enhancing clavicular stability.
The lateral end, or acromial end, of the clavicle articulates with the acromion process of the scapula via the acromioclavicular joint, facilitating shoulder mobility.
On the inferior surface of the lateral clavicle, two key anatomical features—the conoid tubercle and trapezoid line—serve as attachment sites for coracoclavicular ligaments, which play a critical role in scapuloclavicular stability.
Osteological Features of the Clavicle
- Shaft – S-shaped main structure
- Sternal Facet – Articulates with the sternum
- Costal Facet – Contact surface for the first rib
- Costal Tuberosity – Roughened area for ligament attachment
- Acromial End – Lateral articulation with the scapula
- Acromial Facet – Articulates with the acromion process
- Conoid Tubercle – Attachment site for the conoid ligament
- Trapezoid Line – Site for the trapezoid ligament attachment
The sternum and clavicle serve structural and functional roles in the stabilization and mobility of the upper limb. The sternoclavicular joint acts as the primary connection between the axial skeleton and upper extremity, ensuring effective force transmission and movement coordination.