Clavicle

You have two collarbones.

They are long and thin. They have an S shape. They connect your arm to your body. These bones act like a brace. They hold your shoulder blade in place. This helps your arm hang free.

They can break if you fall. A hit to the shoulder can break them too. It is the most common broken bone. Can you feel yours?

You have two collarbones. People also call them clavicles.

These bones are long and thin. They have a unique S shape. The clavicle is the only long bone that lies flat.

These bones act like a strut. A strut is a bar that holds things in place. The clavicle connects your arm to your chest. It connects your shoulder blade to your breastbone. This helps your arm hang free. It also lets your shoulder move easily.

The clavicle is the most common broken bone. It can break if you fall on an outstretched arm. A direct hit to the shoulder can break it too. The weakest part is where the bone curves.

In birds, these bones join together. They make a Y-shaped bone called a furcula. Most people know this as a wishbone.

These bones start to form very early. They begin to grow when a baby is still in the womb. They do not finish growing until you are about 21 to 25 years old.

The clavicle is a slender bone with a unique S shape.

Many people call it the collarbone or the keybone. It is a very special long bone because it lies horizontally. Most other long bones in your body stand up or down. You have two clavicles, one on each side of your body. They work together with your shoulder blade to form the shoulder girdle. This structure is very important for how your upper body moves.

Think of the clavicle as a sturdy strut or a support bar. It connects your arm to the middle of your body. One end connects to the sternum, which is your breastbone. The other end connects to the acromion on your shoulder blade. This connection keeps your shoulder blade in place so your arm can hang freely. It also acts like a crane to help your shoulder move. This allows your arm to stay away from your chest. This movement gives your arm a wide range of motion.

These bones start forming very early in life. They begin to grow during the fifth and sixth weeks of an embryo's development. This process is called ossification, which means laying down minerals to make bone. The clavicle is actually the first bone to start this process. However, it is also one of the last to finish. Most people do not finish growing their collarbones until they are 21 to 25 years old.

There are many interesting facts about how these bones look and work. The bone has a medial end and a lateral end. The medial end is the longest part of the shaft. The lateral end is the widest part but also the thinnest part. Scientists have found that males usually have larger and longer clavicles than females. A study of 748 males and 252 females showed these size differences. The left clavicle is often longer and weaker than the right one.

Nature uses these bones in many different ways. In birds, the two clavicles fuse together into one Y-shaped bone. This bone is called the furcula, but you might know it as a wishbone.

Some animals, like crocodiles and salamanders, do not have clavicles at all. In turtles, these bones actually help form their hard outer shells. Even in dinosaurs, the clavicle played a role in how their shoulders worked. It is a bone that has changed a lot through history.

The clavicle, often called the collarbone or keybone, is a slender, S-shaped long bone.

It is unique because it is the only long bone in the human body that lies horizontally. There are two clavicles, one located on each side of the body. Together with the scapula, or shoulder blade, they form the shoulder girdle. This structure is vital for connecting the upper limb to the axial skeleton. It serves as a mechanical strut that keeps the scapula in place. This allows the arm to hang freely and move through a wide range of motion.

To understand how it works, look at its two ends and its central shaft. The medial end, also called the sternal end, is rounded and quadrangular. It connects to the manubrium of the sternum at the sternoclavicular joint. The lateral end, or acromial end, is flattened and wider than the rest of the bone. It connects to the acromion of the scapula at the acromioclavicular joint. The shaft itself is divided into two main regions. The medial region is the longest, making up two-thirds of the entire shaft. The lateral region is the widest part of the bone, but it is also the thinnest.

The clavicle acts like a flexible, crane-like strut for the body. It transmits physical impacts from the upper limb to the rest of the skeleton. It also protects the neurovascular bundle, which is a group of nerves and blood vessels. This bundle is located in the cervicoaxillary canal and supplies the upper limb. The bone's S-shape allows it to rotate along its axis. This rotation occurs when the shoulder is abducted, or moved away from the body. This movement is why the bone was named 'clavicula,' which means 'little key' in Latin.

Developmentally, the clavicle is quite remarkable. It is the very first bone to begin ossification during embryonic development. Ossification is the process of laying down minerals onto a preformed matrix to create bone. This begins during the fifth and sixth weeks of gestation. However, it is also one of the last bones to finish this process. Most people do not complete ossification until they are between 21 and 25 years old. The bone consists of a mass of cancellous bone surrounded by a compact bone shell. The lateral end forms through intramembranous ossification, while the medial end forms through endochondral ossification.

Many muscles and ligaments attach to the clavicle to provide stability. On the lateral end, the deltoid muscle attaches to the deltoid tubercle. The trapezius muscle attaches to the posterior border of the lateral region. On the inferior surface, the subclavius muscle attaches to the subclavian groove. There are also specific attachment sites like the trapezoid line and the conoid tubercle. These sites hold the trapezoid and conoid ligaments in place. These ligaments are part of the coracoclavicular ligament. This ligament connects the collarbone to the coracoid process of the scapula.

Because of its position, the clavicle is the most commonly broken bone in the body. Fractures often happen from a direct hit to the shoulder. They also occur when a person falls on outstretched arms. The most common site for a fracture is the junction between the two curves. This is the weakest point of the bone. In some cases, the sternocleidomastoid muscle can lift the broken piece upward. This movement can even perforate the overlying skin. Doctors also use the mid-clavicular line as a medical reference. This vertical line helps them locate the gallbladder or evaluate the heart.

The history of this bone shows how much animals have changed over time. In primitive bony fish, the clavicle is associated with the pectoral fin. In birds, the two clavicles have fused into a single Y-shaped bone. This structure is called the furcula, which is commonly known as a wishbone. In dinosaurs, the clavicle was present in saurischian groups. However, it was largely absent in ornithischian dinosaurs. Some mammals have even reduced or lost their clavicles entirely. This loss allows the scapula more freedom to move, which helps with fast running. The clavicle remains a fascinating example of biological engineering across many species.