What Is Collar Bone?

Collar bone, also known as the clavicle, is a thin S-shaped bone that is present between the breastbone and shoulder blade. It is almost 6 inches long and is the only bone that lies horizontally in our body. The collarbones are found in pairs, one towards the left and the other to the right.

Along with the shoulder blade, the collar bone forms the shoulder girdle. The collar bones are distinctly visible in people who have less fat in the neck region and bulges from the skin. However, it is the most commonly fractured bone if affected by falling or overstretching.

Anatomy

The collar bone is a slender, doubly curved bone that joins the arm to the central portion of the body. It is found just above the first rib and functions as a strut to keep the shoulder blade in place so that the arm can hang freely.

The collar bone can be divided into the medial end, lateral end and shaft.

Shaft

The shaft of the collar bone is the point of attachment for muscles such as deltoid trapezius, etc.

Medial End

The medial region, also known as the sternal region, is rounded. It has a long curve that goes anteriorly and laterally along two-thirds portions of the entire shaft. It is the longest clavicular region.

The medial end is quadrangular in shape and joins with the clavicular notch of the sternum to form the sternoclavicular joint. The medial end has a concave anterior border that gives rise to deltoid muscles and a convex posterior border that gives rise to the trapezius muscle.

Lateral End

The lateral end, also known as the acromial end, is a flat surface of the shaft that has a large posterior curve that articulates with the acromion of the scapula. The flat surface of the lateral end articulates with the shoulder to form the acromioclavicular joint. It is the thinnest and widest region of the collar bone.

The lateral end has a ridge on its inner surface called the trapezoid line and a rounded projection called the conoid tubercle. Both of these surfaces act as the site of attachment for ligaments and tendons for the shoulder.

Types of Collar Bone

The shape of the collar bones differs compared to other bones. They are usually longer in males than in females. The bone ossification of the collar bone completes at the age of about 25 years.

The left clavicle is sometimes longer and weaker than the right bone. In a condition called cleidocranial dysostosis, the collar bones are partially or completely absent. Around 2-3% of people have a vestigial levator claviculae muscle.

Functions

It supports the scapula and the suspended limb and thus allows free movement of the limb. It keeps the limb away from the thorax, thus functioning as a flexible strut for the scapula.
It protects the canal from where the neurovascular bundle for the limb passes.
It avoids hits to the upper limb by transferring physical impacts to the axial skeleton.

In Other Animals

The collar bone first appeared in bony fish as paired bones, running below and behind the gills on each side and joined by a fusion. They are, however, absent in cartilaginous fish.

Tetrapods have clavicles, along with an interclavicle that is diamond-shaped and present between the base of the two bones. It is entirely absent in amphibians. The interclavicle is not seen in marsupials and placental mammals.

Birds have clavicles that are known as wishbones or furcula, where the two bones are fused.

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Frequently Asked Questions

What is the other name of the collar bone?

The collar bone is also known as the clavicle.

Why is the collar bone called a beauty bone?

The collar bone is also known as the beauty bone because of its prominent location on the body and the curvatures that give it an elongated shape.

How serious is a broken collarbone?

A fracture in the collarbones is usually not serious and can heal by itself if proper care is taken. However, it can be complicated if there is any injury in the underlying muscles or blood vessels.