SCAPULA: osteology,myology, ossification, clinical anatomy.

Bone: scapula

• Also called shoulder blade , blade bone.
• Triangular plate of bone lying over the upper ribs in the back. It partly covers the 2nd to 7th rib.

Side determination

• The body of the scapula is flat triangular in shape.
• The upper part of the body is broad(inferior of the triangle).
• The lower part of the body is pointed(apex of the triangle).
• The body has two surfaces the anterior surface is smooth and the posterior surface is rough.
• The posterior surface contain a larger projection called spine.
• The lateral angle is enlarged and bears a large shallow depression called glenoid cavity.

Osteology 

• Scapula consist of

1. Body 
2. Processes
3. Glenoid cavity

Body 

• It is triangular in shape .
• It has two surfaces three borders and three angles.
• The two surfaces are anterior surface and posterior surface.
• The anterior surface also called costal surface is smooth and consist of a fossa called subscapular fossa(fossa gives attachment to subscapular muscle).
• The posterior or dorsal surface of the bone is rough .
• It gives off a large projection called spine of the scapula.
• The spine of the scapula divides the dorsal surface of the scapula into two supraspinous fossa and infraspinous fossa.
• The supraspinous fossa and infraspinous fossa communicate with each other through spinoglenoid notch(located on the lateral side of the notch).
• The three angles of the scapula are superior, interior and lateral angle.
• The superior angle is at the junction between the superior and medial border.
• The inferior angle is at the junction of the medial and lateral borders.
• The lateral angle is at the junction of the medial and the lateral borders.
• It is also called glenoid angle since it carries glenoid fossa .

• The superior border extends between superior angle and the lateral angle .
• It is thin and sharp.
• It is separated from glenoid fossa by the root of the coracoid process.
• A deep suprascapular notch is seen close to the lateral end of the superior border.
• The medial border also called vertebral border.
• It extends from the superior angle to inferior angle.
• It is arched and thicker than the superior border.
• The lateral border also called axillary border.
• It runs from the lateral angle to the inferior angle.
• The part of the body adjoining the lateral border is thickened to form a longitudinal bar of bone  called the strengthening bar.

Glenoid cavity

• Shallow articular socket of the head of the humerus present at the lateral angle of the scapula.
• Below the cavity the lateral border shows  shows a rough riders area called the supraglenoid tubercle.
• The slightly constructed area immediately medial to it constitutes the neck.

Process of scapula

Scapula contains three process

1. Spinous process:

• Large triangular projection from the posterior surface of the body.
• The spine consist of two borders anterior and posterior border.
• The anterior border of the spine is attached to the dorsal surface of the body.
• The posterior border is free and greatly thickened to form crest of the spine.
• It is broad and flat ,has upper lips and lower lips.
• The medial end of the spine lies near the medial border of the scapula and is often referred to as the root of the spine.
• The lateral border is free,broad and forms the medial boundary of the spinoglenoid notch .

2. Acromion process

• Foreward directed lateral end of the spine.
• It has two borders medial and lateral borders and two surfaces upper surface and lower surface.
• The medial border shows the presence of small oval faster for the articulation with the lateral end of the clavicle.

3.coracoid process

• Bent finger shape.
• The root of this process attached to the body of the scapula just above the glenoid cavity.
• The lower part of the process is marked by supraglenoid tubercle.
• The tip of the coracoid process is directed foreward, laterally and little downward.

Myology

Costal surface of the scapula:
Origin:

• Subscapularis arises from the subscapular fossa.

Insertion:

• The serratus anterior is inserted into the costal surface along the medial border.

Dorsal surface of the scapula:
Origin:

• Supraspinatus muscle originates from the supraspinous fossa.
• Infraspinous muscle arise from the infraspinous fossa.
• Triceps (long head) arise from the infraglenoid tubercle.
• Teres minor arise from the upper 2/3rd of the dorsal aspect of lateral border.
• Teres major arise from the lower 1/3rd of the dorsal aspect of the lateral border.
• The lattisimus dorsi arise from the dorsal surface of the inferior angle.

Insertion:

• The levator scapulae is inserted into a narrow strip extending from the superior angle to the level of the root of the spine in the dorsal aspect of the medial border.
• The rhomboideus minor is inserted opposite the root of the spine at the dorsal aspect of the medial border.
• The rhomboideus major is inserted from the root of the spine to the inferior angle in the dorsal aspect of the medial.

Coracoid process:

Origin:

• Biceps brachii (short head) arises from the lateral part of the tip of the coracoid process.
• Biceps brachii(long head) arise from the long head from the supra glenoid tubercle.
• The coracobrachialis arises from the medial part of the tip of the coracoid process.

• The inferior belly of the omohyoid arises from the infraglenoid tubercle.
• The trapezius gets inserted into the upper border of the crest of the spine and into the medial border of the acromion.

Ossification

• Scapula has 1 primary center and 7 seven secondary centres.
• The primary centres appear in the region of the body during 8th week of foetal life.
• Spine: ossified by an extension from the primary center.
• Coracoid process: ossified from a secondary centre that appears in the 1st year.
• The remaining secondary centres appear at puberty ;one for the subcoracoid area including the glenoid,two for the acromion,one for medial border and one for inferior angle.
• All the secondary centres fuse between the age of 18th and 22nd .

Clinical anatomy

• Sprengel's shoulder: condition in which scapula is placed higher than normal (elevated scapula)
• Winging of scapula:(scapula alata) condition in which the medial border of the scapula is lifted off the chest wall; caused due to the paralysis of the serratus anterior muscle.
• Non union of epiphysis: usually involves one of the acromial centres.