Clavicle Bone
Anatomy Lesson
Introduction
The clavicle or collarbone is a long bone that extends horizontally from the manubrium (upper part) of the sternum to the acromion of the scapula. The clavicle and scapula comprise the shoulder (pectoral) girdle.
Clavicle Functions
The clavicle performs several essential functions. (1) The horizontally positioned clavicle holds the shoulder joint superiorly and laterally from the body trunk, allowing maximum freedom of movement for the upper limb. (2) Anchored by muscles from above, the clavicle functions like a strut that extends laterally to support the scapula. (3) The clavicle also transmits forces acting on the upper limb to the sternum and axial skeleton. (4) Additionally, the clavicle protects the underlying nerves and blood vessels as they pass between the body’s trunk and the upper limb.
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Clavicle Shape
The clavicle bone has two ends: a round medial end and a flattened lateral end. Connecting the two ends is a central cylindrical shaft. The medial end curves forward while the lateral end curves backward, giving the bone an S-shaped appearance. Inferior or superior views of the bone best show the curvatures.
Right Clavicle Shape and Orientation
Lateral End Shaft Medial End
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Clavicular Joints
The clavicle forms joints with other bones at its medial and lateral ends.
The medical end of the clavicle articulates with the superior portion of the sternum (manubrium) to form the sternoclavicular joint. This joint is the only bony articulation between the pectoral girdle of the upper limb and the axial skeleton. This joint allows considerable mobility, enabling the shoulder to move up and down, forward and backward, and rotate forward and backward.
The lateral end of the clavicle bone articulates with the acromion, a superior projection of the scapula bone, to form the acromioclavicular joint.
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Clavicular Ligaments
The anterior and posterior sternoclavicular ligaments attach the clavicle to the manubrium of the sternum at the sternoclavicular joint. The costoclavicular ligament, which extends from the lateral end of the clavicle to the underlying first rib, helps stabilize the junction.
The superior and inferior acromioclavicular ligaments attach the clavicle to the acromion of the scapula at the acromioclavicular joint. The acromioclavicular joint transmits forces from the upper limb to the clavicle, and the attachment provided by the acromioclavicular ligaments is relatively weak. A hard fall onto the elbow or outstretched hand can stretch or tear the acromioclavicular ligaments. Another nearby ligament, the coracoclavicular ligament, provides additional strength to the joint. This ligament connects the coracoid process of the scapula to the inferior clavicle, and it consists of two parts: the anterior trapezoid ligament and the posterior conoid ligament.
Lateral Ligaments
Medial Ligaments
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Clavicle Landmarks
Elevations and depressions on the inferior surface of the clavicle provide attachment points for muscles and ligaments that control the bone’s movement.
An indentation called the subclavian groove extends along the clavicle’s inferior shaft. It is an attachment site for the subclavius muscle, which originates on the first rib. This muscle stabilizes the clavicle while other muscles move the arm (humerus) at the shoulder joint.
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Three elevations on the underside of the clavicle serve as attachment sites for ligaments that help stabilize the clavicular joints at the scapula and sternum.
On the lateral side of the bone, the trapezoid line (ridge) runs diagonally (forward and laterally), providing attachment to the trapezoid ligament. Medial to the trapezoid line is the conoid tubercle. This bump-like elevation is an attachment point for the conoid ligament.
The costal tuberosity (or impression for costoclavicular ligament) is on the medial side of the clavicle. This broad, roughed surface is the attachment site for the costoclavicular ligament.
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Clavicle Quizzes
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References and Attributions
NIH: National Library of Medicine – “Anatomy, Bone Markings.”
NIH: National Library of Medicine – “Anatomy, Shoulder and Upper Limb, Clavicle.”
NIH: National Library of Medicine – “Anatomy, Should and Upper Limb, Sternoclavicular Joint.”
OpenStax – “The Pectoral Girdle” (Access for free at https://openstax.org/books/anatomy-and-physiology-2e/pages/1-introduction).
ScienceDirect – “Clavicle.”
ScienceDirect – “Sternoclavicular Joint.”