Scapula

You have two shoulder blades.

They are flat bones. They help your arm move. These bones connect to your collar bone. They also connect to your arm bone.

Many muscles stick to these bones. These muscles help you turn your shoulder. They also help you lift your arm. The bones look like small shovels.

You can feel them on your back. They are very important for moving your body.

You have two shoulder blades. These bones are called the scapula.

They are flat and shaped like a triangle. Each bone sits on one side of your back. They connect your collar bone to your upper arm bone.

The name scapula comes from a word for a small shovel. This is because the bone looks like a shovel.

Many muscles attach to the scapula. These muscles help you move your arms. Some muscles help you turn your shoulder. Other muscles help you lift your arm. Some muscles help keep the bone steady.

The bone has different parts. It has a thick part called the head. The head has a shallow pit. This pit connects to your arm bone. The top of the bone is the acromion. This part forms the very top of your shoulder.

Your scapula grows as you get older. It starts as soft parts called cartilage. Over time, these parts turn into hard bone. This process is called ossification. Most of the bone is hard by birth. But some parts do not turn to bone until you are older. Some parts finish growing when you are twenty years old.

The scapula is a very important bone in your body. Most people call it the shoulder blade.

It is a flat bone shaped like a triangle. This bone sits on the back part of your chest wall. The scapula connects your collar bone to your upper arm bone.

There are two scapulae in your body. They are mirror images of each other on each side. The name comes from a Latin word for a small shovel or trowel.

Many different muscles attach to this bone to help you move. There are three main groups of muscles. The first group is called intrinsic muscles. These include the rotator cuff muscles like the subscapularis and supraspinatus. They help you rotate your shoulder joint.

The second group is called extrinsic muscles. These include your biceps, triceps, and deltoid muscles. They help with many actions of the shoulder joint. The third group helps with stabilizing and rotating the bone itself. These include the trapezius and rhomboid muscles.

Scientists and doctors use special names to describe this bone. In medical terms, the prefix omo- is used for the shoulder blade. This prefix comes from the Ancient Greek word ōmos, which means shoulder.

The bone has several different parts and edges. It has two main surfaces called the front and the back. The back is divided into two parts by a ridge called the spine. This spine creates a top area called the supraspinous fossa. It also creates a larger bottom area called the infraspinous fossa.

The scapula has three corners called angles. The top angle is near your second thoracic vertebra. The bottom angle is the lowest part of the bone.

The third angle is the thickest part called the head. The head has a shallow pit called the glenoid cavity. This pit connects to the head of your arm bone. The very top of your shoulder is the acromion. This is a large part that curves forward and upward.

Your scapula grows in a way called ossification. This is when soft parts turn into hard bone. The bone starts growing when you are still a fetus. The main body starts to form around the second month of life.

Most of the bone is already hard at birth. However, some parts like the acromion are still soft cartilage. These parts turn to bone as you grow up. The coracoid process joins the rest of the bone around age 15. The very last parts usually finish growing between ages 14 and 20.

The scapula, commonly known as the shoulder blade, is a critical component of the human shoulder girdle.

This flat, roughly triangular bone connects the clavicle, or collar bone, to the humerus, which is the upper arm bone.

Because humans have two shoulders, the scapulae are paired structures. Each bone is a near mirror image of the other on opposite sides of the body. The name itself comes from the Classical Latin word for a trowel or small shovel. In medical contexts, professionals often use the prefix "omo-" to refer to the shoulder. This prefix is derived from the Ancient Greek word "ōmos," meaning shoulder.

Structurally, the scapula serves as a massive attachment site for three distinct groups of muscles. The first group is the intrinsic muscles, which include the rotator cuff muscles. These are known as the SITS muscles: the subscapularis, supraspinatus, infraspinatus, and teres minor. These muscles attach directly to the bone surface to manage internal and external rotation of the shoulder.

The second group consists of extrinsic muscles like the biceps, triceps, and deltoid. These attach to specific landmarks like the coracoid process and the spine of the scapula. Finally, a third group of muscles, including the trapezius and serratus anterior, handles the stabilization and rotation of the scapula itself.

The bone features two primary surfaces: the anterior (front) and the posterior (back) surfaces. The anterior surface is called the subscapular fossa, which is a broad, concave area. This area contains longitudinal ridges that help the subscapularis muscle attach firmly.

The posterior surface is divided into two unequal sections by a prominent ridge called the spine. The area above this spine is the supraspinous fossa, while the larger area below is the infraspinous fossa.

These two fossae are connected by a small opening known as the spinoglenoid notch. This notch helps facilitate the passage of nerves and blood vessels through the bone.

There are three specific angles that define the shape of the scapula. The superior angle is located near the second thoracic vertebra and is covered by the trapezius muscle.

The inferior angle is the lowest point of the bone and moves forward during arm movement. The third is the lateral angle, also called the glenoid angle, which is the thickest part of the bone. This area houses the glenoid cavity, a shallow socket that articulates with the head of the humerus.

To help the joint stay stable, a structure called the glenoidal labrum deepens this cavity. At the very top of the shoulder sits the acromion, a large process that overhangs the glenoid cavity.

The edges of the bone, or borders, are also highly specialized. The superior border is the shortest and thinnest, containing a semicircular notch called the scapular notch. This notch often becomes a hole, or foramen, through which the suprascapular nerve passes.

The axillary border is the thickest of the three edges and runs down toward the inferior angle. It features a rough area called the infraglenoid tuberosity, where the long head of the triceps brachii attaches. The medial border is the longest edge, stretching from the top to the bottom of the bone. This border provides a long attachment site for muscles like the serratus anterior and the rhomboids.

Developing the scapula is a complex process called ossification, where cartilage turns into hard bone. This process begins while a person is still a fetus, starting with the main body of the bone.

While much of the scapula is bone at birth, several parts remain as flexible cartilage. These include the glenoid cavity, the coracoid process, and the acromion. The coracoid process typically joins the rest of the bone around the 15th year of life.

The remaining parts of the bone undergo ossification in quick succession between the ages of 14 and 20. This ensures the shoulder is fully strengthened as a person reaches adulthood.

The scapula is a masterpiece of biological engineering that balances strength with mobility. By providing a stable base for the arm while allowing for wide ranges of motion, it enables almost all upper-body movement. The way the bone is shaped—with its various fossae, processes, and ridges—allows it to host a complex network of muscles. These muscles work together to rotate, lift, and stabilize the entire shoulder complex. Without the specific architecture of the scapula, the intricate movements of the human arm would not be possible.