The acromion process, or simply the acromion (from Greek: akros, "highest", ōmos, "shoulder"), is an anatomical

Anatomy

Anatomy is a branch of biology and medicine that is the consideration of the structure of living things. It is a general term that includes human anatomy, animal anatomy , and plant anatomy...

 feature on the shoulder blade (scapula

Scapula

In anatomy, the scapula , omo, or shoulder blade, is the bone that connects the humerus with the clavicle ....

), together with the coracoid process extending laterally over the shoulder joint

Glenohumeral joint

The glenohumeral joint, or shoulder joint, is a multiaxial synovial ball and socket joint and involves articulation between the glenoid fossa of the scapula and the head of the humerus...

.

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

Acromioclavicular joint

The acromioclavicular joint, or AC joint, is a joint at the top of the shoulder. It is the junction between the acromion and the clavicle. -Function:...

.

The acromion forms the summit of the shoulder

Shoulder

The human shoulder is made up of three bones: the clavicle , the scapula , and the humerus as well as associated muscles, ligaments and tendons. The articulations between the bones of the shoulder make up the shoulder joints. The major joint of the shoulder is the glenohumeral joint, which...

, and is a large, somewhat triangular or oblong

Rectangle

In Euclidean plane geometry, a rectangle is any quadrilateral with four right angles. The term "oblong" is occasionally used to refer to a non-square rectangle...

 process, flattened from behind forward, projecting at first lateralward, and then curving forward and upward, so as to overhang the glenoid cavity

Glenoid cavity

The glenoid cavity is a shallow pyriform, articular surface, which is located on the lateral angle of the scapula. It is directed laterally and forward and articulates with the head of the humerus; it is broader below than above and its vertical diameter is the longest.This cavity forms the...

.

Surfaces

• Its superior surface, directed upward, backward, and lateralward, is convex, rough, and gives attachment to some fibers of the Deltoideus
  Deltoid muscle
  In human anatomy, the deltoid muscle is the muscle forming the rounded contour of the shoulder. Anatomically, it appears to be made up of three distinct sets of fibers though electromyography suggests that it consists of at least seven groups that can be independently coordinated by the central...
  
  , 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
  Clavicle
  In human anatomy, the clavicle or collar bone is a long bone of short length that serves as a strut between the scapula and the sternum. It is the only long bone in body that lies horizontally...
  
  .

Os acromiale

In childhood the acromion has a separate center of ossification and is joined to the rest of the scapula by cartilage

Cartilage

Cartilage is a flexible connective tissue found in many areas in the bodies of humans and other animals, including the joints between bones, the rib cage, the ear, the nose, the elbow, the knee, the ankle, the bronchial tubes and the intervertebral discs...

. Rarely, the acromion stays in adulthood as a separate bone called "os acromiale". This feature was common in skeletons recovered from the Mary Rose

Mary Rose

The Mary Rose was a carrack-type warship of the English Tudor navy of King Henry VIII. After serving for 33 years in several wars against France, Scotland, and Brittany and after being substantially rebuilt in 1536, she saw her last action on 1545. While leading the attack on the galleys of a...

 shipwreck

Shipwreck

A shipwreck is what remains of a ship that has wrecked, either sunk or beached. Whatever the cause, a sunken ship or a wrecked ship is a physical example of the event: this explains why the two concepts are often overlapping in English....

: it is thought that in those men, much archery

Archery

Archery is the art, practice, or skill of propelling arrows with the use of a bow, from Latin arcus. Archery has historically been used for hunting and combat; in modern times, however, its main use is that of a recreational activity...

 practice from childhood on with the mediaeval war bow

Longbow

A longbow is a type of bow that is tall ; this will allow its user a fairly long draw, at least to the jaw....

 (which needs a pull 3 times as strong as the modern standard Olympic

Olympic Games

The Olympic Games is a major international event featuring summer and winter sports, in which thousands of athletes participate in a variety of competitions. The Olympic Games have come to be regarded as the world’s foremost sports competition where more than 200 nations participate...

 bow

Bow (weapon)

The bow and arrow is a projectile weapon system that predates recorded history and is common to most cultures.-Description:A bow is a flexible arc that shoots aerodynamic projectiles by means of elastic energy. Essentially, the bow is a form of spring powered by a string or cord...

) pulled at the acromion so much that it prevented bony fusion of the acromion with the scapula.

In animals

The acromion process of bat

Bat

Bats are mammals of the order Chiroptera "hand" and pteron "wing") whose forelimbs form webbed wings, making them the only mammals naturally capable of true and sustained flight. By contrast, other mammals said to fly, such as flying squirrels, gliding possums, and colugos, glide rather than fly,...

s (Mammalia: Chiroptera) is particularly elongated compared to that of human

Human

Humans are the only living species in the Homo genus...

s.