The shoulder blade is made of the scapula.

The shoulder blade, also known as the scapula, is a flat, triangular-shaped bone located on the back of the shoulder. It plays a crucial role in the movement and stability of the shoulder joint. The scapula forms the posterior part of the shoulder girdle, along with the clavicle or collarbone.

Here is a detailed explanation of the components of the shoulder girdle:

1. Clavicle:
The clavicle or collarbone is a long, S-shaped bone that connects the sternum (breastbone) to the scapula. It forms the anterior part of the shoulder girdle and helps to transmit forces from the upper limb to the axial skeleton. The clavicle acts as a strut, providing support, mobility, and protection to the underlying structures.

2. Scapula:
The scapula is a large, triangular bone situated on the back of the shoulder. It is located between the second and seventh ribs and is held in place by various muscles. The scapula has several important features, including the spine, acromion process, coracoid process, and glenoid cavity.

- The spine of the scapula is a prominent ridge that runs diagonally across the posterior surface. It divides the scapula into two main regions: the supraspinous fossa above the spine and the infraspinous fossa below the spine. These fossae provide attachment sites for muscles and ligaments.

- The acromion process is a bony projection that extends from the spine of the scapula. It forms the outer tip of the shoulder and connects with the clavicle, forming the acromioclavicular joint.

- The coracoid process is a hook-like structure that projects anteriorly from the scapula. It serves as an attachment point for muscles and ligaments involved in shoulder movement and stability.

- The glenoid cavity is a shallow, concave depression located on the lateral aspect of the scapula. It forms the socket of the shoulder joint and articulates with the head of the humerus (upper arm bone).

3. Humerus:
While the humerus is not part of the scapula, it is an important bone in the context of the shoulder joint. The humerus is the largest bone of the upper limb and forms the connection between the scapula and the forearm bones (radius and ulna). It articulates with the glenoid cavity of the scapula to form the shoulder joint, allowing for a wide range of arm movements.

In conclusion, the shoulder blade is made up of the scapula, along with the clavicle and the humerus, forms the shoulder girdle. The scapula plays a vital role in shoulder movement and stability, while the clavicle and humerus contribute to the overall structure and function of the shoulder joint.