The clavicle (Latin a small key) is a long bone. It supports the shoulder so that the arm can swing clearly away from the trunk. The clavicle transmits the weight of the limb to the sternum. The bone has a cylindrical part called the shaft, and two ends, lateral and medial.
Side Determination of the clavicle bone
The side to which a clavicle belongs can be determined from the following characters.
- The lateral end is flat, and the medial end is large and quadrilateral.
- The shaft is slightly curved so that it is convex forwards in its medial two-thirds and concave forwards in its lateral one-third.
- The inferior surface is grooved longitudinally in its middle one-third.
Peculiarities of the clavicle
- It is the only long bone that lies horizontally.
- It is subcutaneous throughout.
- It is the 1st bone to start ossifying.
- It is the only long bone which ossifies in the membrane.
- It is the only long bone which has 2 primary centers of ossification.
- There is no medullary cavity.
- It is occasionally pierced by the middle supraclavicular nerve.
It receives the weight of upper limb via lateral one-third through the coracoclavicular ligament and transmits the weight of upper limb to the axial skeleton via medial two-third part. See in the flow chart.
Features of the clavicle bone
The Shaft (Fig 1.2a and b) is divisible into the lateral one-third and the medial two-thirds.
The lateral one-third of the Shaft is flattened from above downwards. It has two borders, anterior and posterior. The anterior border is concave forwards. The posterior border is convex backwards. This part of the bone has two surfaces, superior and inferior. The superior surface is subcutaneous and the inferior surface presents an elevation called the conoid tubercle and a ridge called the trapezoid ridge.
The medial two-thirds of the shaft is rounded and is said to have four surfaces. The anterior surface is convex forwards. The posterior surface is smooth. The superior surface is rough in its medial part. The inferior surface has a rough ovel impression at the medial end. The lateral half of this surface has a longitudinal subclavian groove. The nutrient foramen lies at the lateral end of the groove.
Lateral and Medial Ends
- The lateral or acromial end is flattened from above downwards. It bears a fact that articulates with the acromioclavicular joint.
- The medial or sternal end is quadrangular and articulates with the clavicular notch of the manubrium sterni to from the sternoclavicular joint. The articular surface extends to the inferior aspect, for articulation with the first costal cartilage.
Author: Muhammad Parvaiz
Mr. Muhammad Parvaiz is a botanist by profession. He has published many review articles and research papers in well reputed national, international scientific impact factor journals, magazines and newspaper. He is also co-author of a book, i.e. “Introductory Plant Taxonomy”.