Scapula

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Scapula

In anatomy

Anatomy

Anatomy is a branch of biology that is the consideration of the body plan. It is a general term that includes human anatomy, animal anatomy and plant anatomy ....
, the scapula, omo, or shoulder blade, is the bone

Bone

Bones are rigid organ that form part of the endoskeleton of vertebrates. They function to move, support, and protect the various organs of the body, produce red blood cell and white blood cells and store minerals....
that connects the humerus

Humerus

The humerus is a long bone in the arm or forelimb that runs from the shoulder to the elbow.Anatomically, it connects the scapula and the ulna, and consists of the following three sections:...
(arm bone) with the clavicle

Clavicle

In human anatomy, the clavicle or collar bone is classified as a flat bone that makes up part of the shoulder girdle . It receives its name from the Latin clavicula because the bone rotates along its axis like a key when the shoulder is Abduction ....
(collar bone).

The scapula forms the posterior part of the shoulder

Shoulder

In human anatomy, the shoulder joint comprises the part of the body where the humerus attaches to the scapula. The shoulder refers to the group of structures in the region of the joint....
girdle. In human

Human

A human being, also human or man, is a member of a species of bipedalism primates in the family Hominidae . Mitochondrial DNA evidence indicates that modern humans originated in east Africa about 200,000 years ago....
s, it is a flat bone, roughly triangular

Triangle

A triangle is one of the basic shapes of geometry: a polygon with three corners or wikt:vertex and three sides or edges which are line segments....
in shape, placed on a posterolateral aspect of the thoracic cage.

costal or ventral surface [Fig.

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In anatomy

Anatomy

Bone

Humerus

Clavicle

Shoulder

Human

Triangle

Structure

Surfaces

Costal

The costal or ventral surface [Fig. 1] presents a broad concavity, the subscapular fossa.

The medial two-thirds of this fossa are marked by several oblique ridges, which run lateralward and upward. The ridges give attachment to the tendinous insertions, and the surfaces between them to the shelby, of the Subscapularis. The lateral third of the fossa is smooth and covered by the fibers of this muscle.

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Figure 1 : Left scapula. Costal surface.
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Figure 2 : Left scapula. Dorsal surface.
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Figure 3 : Left scapula. Lateral surface.

At the upper part of the fossa is a transverse depression, where the bone appears to be bent on itself along a line at right angles to and passing through the center of the glenoid cavity

Glenoid cavity

On the lateral angle of the scapula is a shallow pyriform, articular surface, the glenoid cavity , which is directed lateralward and forward and articulates with the head of the humerus; it is broader below than above and its vertical diameter is the longest....
, forming a considerable angle, called the subscapular angle; this gives greater strength to the body of the bone by its arched form, while the summit of the arch serves to support the spine

Vertebral column

In human anatomy, the vertebral column is a column of 24 vertebrae, the sacrum, intervertebral discs, and the coccyx situated in the dorsum aspect of the torso, separated by spinal discs....
and acromion.

Dorsal

The dorsal surface [Fig. 2] is arched from above downward, and is subdivided into two unequal parts by the spine; the portion above the spine is called the supraspinatous fossa

Supraspinatous fossa

The supraspinatous fossa of the scapula, smaller than the infraspinatous fossa, is concave, smooth, and broader at its vertebral than at its humeral end; its medial two-thirds give origin to the Supraspinatus....
, and that below it the infraspinous fossa.

The supraspinous fossa, the smaller of the two, is concave, smooth, and broader at its vertebral than at its humeral end; its medial two-thirds give origin to the Supraspinatus.

The infraspinous fossa is much larger than the preceding; toward its vertebral margin a shallow concavity is seen at its upper part; its center presents a prominent convexity, while near the axillary border is a deep groove which runs from the upper toward the lower part. The medial two-thirds of the fossa give origin to the Infraspinatus; the lateral third is covered by this muscle.

The dorsal surface is marked near the axillary border by an elevated ridge, which runs from the lower part of the glenoid cavity, downward and backward to the vertebral border, about 2.5 cm above the inferior angle.

The ridge serves for the attachment of a fibrous septum, which separates the Infraspinatus from the Teres major and Teres minor.

The surface between the ridge and the axillary border is narrow in the upper two-thirds of its extent, and is crossed near its center by a groove for the passage of the scapular circumflex vessels; it affords attachment to the Teres minor.

Its lower third presents a broader, somewhat triangular surface, which gives origin to the Teres major, and over which the Latissimus dorsi glides; frequently the latter muscle takes origin by a few fibers from this part.

The broad and narrow portions above alluded to are separated by an oblique line, which runs from the axillary border, downward and backward, to meet the elevated ridge: to it is attached a fibrous septum which separates the Teres

Teres

Teres I was the first king of the Odrysian state of Thrace. Teres was well-known for his military abilities, and spent much of his life on the battlefield....
muscles from each other.

Borders

There are three borders of the scapula:

The superior border
Superior border of scapula

Of the three borders of the scapula, the superior border is the shortest and thinnest; it is concave, and extends from the medial angle to the base of the coracoid process....
is the shortest and thinnest; it is concave, and extends from the medial angle to the base of the coracoid process. It is referred to as the cranial border in animals.

The axillary border (or "lateral border") is the thickest of the three. It begins above at the lower margin of the glenoid cavity
Glenoid cavity

On the lateral angle of the scapula is a shallow pyriform, articular surface, the glenoid cavity , which is directed lateralward and forward and articulates with the head of the humerus; it is broader below than above and its vertical diameter is the longest....
, and inclines obliquely downward and backward to the inferior angle. It is referred to as the caudal border in animals.

The vertebral border (or "medial border") is the longest of the three, and extends from the medial to the inferior angle. It is referred to as the dorsal border in animals.

Angles

There are three angles:

The medial angle (or "superior angle"); craneal angle in animals.

The inferior angle; caudal angle in animals.

The lateral angle; distal or articullary angle in animals.

The acromion

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.

Development

The larger part of the scapula undergoes membranous ossification.. Some of the outer parts of the scapula are cartilagenous at birth, and would therefore undergo endochondral ossification . See also ossification of scapula

Ossification of scapula

The scapula is ossified from seven or more centers: one for the body, two for the coracoid process, two for the acromion, one for the vertebral border, and one for the inferior angle....

The head, processes, and the thickened parts of the bone, contain cancellous tissue; the rest consists of a thin layer of compact tissue.

The central part of the supraspinatous fossa and the upper part of the infraspinatous fossa

Infraspinatous fossa

The infraspinatous fossa of the scapula is much larger than the supraspinatous fossa; toward its vertebral margin a shallow concavity is seen at its upper part; its center presents a prominent convexity, while near the axillary border is a deep groove which runs from the upper toward the lower part....
, but especially the former, are usually so thin as to be semitransparent; occasionally the bone is found wanting in this situation, and the adjacent muscles are separated only by fibrous tissue.

Muscular attachments

The following muscles attach to the scapula:

Muscle	Direction	Region >- \| Pectoralis Minor	insertion	coracoid process \|- \| Coracobrachialis	origin	coracoid process \|- \| Serratus Anterior Serratus anterior muscle The serratus anterior is a muscle that originates on the surface of the upper eight or nine ribs at the side of the chest and inserts along the entire anterior length of the medial border of the scapula....	insertion	medial border Medial border of scapula The medial border of the scapula is the longest of the three borders, and extends from the Superior angle of scapula to the inferior angle.It is arched, intermediate in thickness between the superior and the axillary borders, and the portion of it above the Vertebral column forms an obtuse angle with the part below.... \|- \| Triceps Brachii (long head)	origin	infraglenoid tubercle Infraglenoid tubercle The infraglenoid tubercle is the part of the scapula to which the long head of the triceps brachii attaches.External links ... \|- \| Biceps Brachii Biceps brachii muscle In human anatomy, the biceps brachii is a muscle located on the upper arm. The biceps has several functions, the most important being to rotate the forearm and to flex the elbow.... (short head)	origin	coracoid process \|- \| Biceps Brachii Biceps brachii muscle In human anatomy, the biceps brachii is a muscle located on the upper arm. The biceps has several functions, the most important being to rotate the forearm and to flex the elbow.... (long head)	origin	supraglenoid tubercle Supraglenoid tubercle The supraglenoid tubercle is a region of the scapula to which the long head of the biceps brachii muscle attaches.External links ... \|- \| Subscapularis	origin	subscapular fossa Subscapular fossa The costal or ventral surface of the scapula presents a broad concavity, the subscapular fossa.It provides an attachment for the subscapularis muscle.... \|- \| Rhomboid Major Rhomboid major muscle The rhomboid major is a muscle on the back that connects the scapula with the vertebrae of the spinal column....	insertion	medial border Medial border of scapula The medial border of the scapula is the longest of the three borders, and extends from the Superior angle of scapula to the inferior angle.It is arched, intermediate in thickness between the superior and the axillary borders, and the portion of it above the Vertebral column forms an obtuse angle with the part below.... \|- \| Rhomboid Minor Rhomboid minor muscle The Rhomboideus minor arises from the lower part of the ligamentum nuch? and from the spinous processes of the seventh cervical and first thoracic vertebr?....	insertion	medial border Medial border of scapula The medial border of the scapula is the longest of the three borders, and extends from the Superior angle of scapula to the inferior angle.It is arched, intermediate in thickness between the superior and the axillary borders, and the portion of it above the Vertebral column forms an obtuse angle with the part below.... \|- \| Levator Scapulae Levator scapulae muscle The levator scapulae is situated at the back and side of the neck....	insertion	medial border Medial border of scapula The medial border of the scapula is the longest of the three borders, and extends from the Superior angle of scapula to the inferior angle.It is arched, intermediate in thickness between the superior and the axillary borders, and the portion of it above the Vertebral column forms an obtuse angle with the part below.... \|- \| Trapezius	insertion	spine of scapula Spine of scapula The spine of the scapula is a prominent plate of bone, which crosses obliquely the medial four-fifths of the scapula at its upper part, and separates the Supraspinatous fossa from the infraspinatous fossa.... \|- \| Deltoid Deltoid muscle In human anatomy, the deltoid muscle is the muscle forming the rounded contour of the shoulder.It was previously called the Deltoideus and the name is still used by some anatomists....	origin	spine of scapula Spine of scapula The spine of the scapula is a prominent plate of bone, which crosses obliquely the medial four-fifths of the scapula at its upper part, and separates the Supraspinatous fossa from the infraspinatous fossa.... \|- \| Supraspinatus Supraspinatus muscle The supraspinatus is a relatively small muscle of the upper limb that takes its name from its origin from the supraspinous fossa superior to the spine of the scapula....	origin	supraspinous fossa \|- \| Infraspinatus	origin	infraspinous fossa \|- \| Teres Minor	origin	lateral border \|- \| Teres Major	origin	lateral border \|- \| Latissimus Dorsi (a few fibers)	origin	inferior angle \|- \| Omohyoid	origin	superior border Superior border of scapula Of the three borders of the scapula, the superior border is the shortest and thinnest; it is concave, and extends from the medial angle to the base of the coracoid process....

Movements

Movements of the scapula are brought about by scapular muscles:

Elevation, Depression, Protraction, Retraction, Lateral rotation, Medial rotation, Upward Rotation, Downward Rotation, Anterior Tipping, and Posterior Tipping

Injury

Because of its sturdy structure and protected location, scapular fractures are uncommon; when they do occur, they are an indication that severe chest trauma

Chest trauma

Chest trauma is a serious injury of the chest. Thoracic trauma is a common cause of significant disability and mortality, the leading cause of death from physical trauma after head and spinal cord injury....
has occurred.

Additional images

External links

Sources

Additions have been made from "Nickel; Schummer; Seiferle; Lehrbuch der Anatomie der Haussäugetiere.