Acromion

The acromion process, or simply the acromion, is an anatomical feature on the scapula.

In humans
It is a continuation of the scapular spine, and hooks over anteriorly.

The acromion articulates with the clavicle to form the acromioclavicular joint.

The acromion forms the summit of the shoulder, and is a large, somewhat triangular or oblong process, flattened from behind forward, projecting at first lateralward, and then curving forward and upward, so as to overhang the glenoid cavity.

Surfaces

 * Its superior surface, directed upward, backward, and lateralward, is convex, rough, and gives attachment to some fibers of the Deltoideus, and in the rest of its extent is subcutaneous.


 * Its inferior surface is smooth and concave.

Borders

 * Its lateral border is thick and irregular, and presents three or four tubercles for the tendinous origins of the Deltoideus.


 * Its medial border, shorter than the lateral, is concave, gives attachment to a portion of the Trapezius, and presents about its center a small, oval surface for articulation with the acromial end of the clavicle.

In animals
The acromion process of bats (Mammalia: Chiroptera) is particularly elongated compared to that of humans.