Acromial bone

The acromial bone (Latin os acromiale, from ancient Greek ἄκρος - “tip, spear point” + μιάλιον - “shoulder”) is a human sesamoid bone located in the acromioclavicular joint. It is a flat triangular bone, with its base directed upward and posteriorly.

The acromial bones are located at the top of the shoulder, between the acromion and the collarbone. They provide strength and stability to the acromion joint and also help support the load on the shoulder joint.

The acromial bone has two surfaces: medial and lateral. The medial surface is covered with articular cartilage and forms the articular surface for articulation with the acromion. The lateral surface is also covered with articular cartilage, but does not have an articular surface.

In addition, the acromial bones have three processes: superior, middle and inferior. The superior process is directed upward and forward and has an articular surface that articulates with the clavicle. The middle process is located between the superior and inferior processes and also has an articular surface. The inferior process is directed downward and backward and does not have an articular surface.