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The Surfaces of Scapula

1. The costal surface or subscapular fossa is concave and is directed medially and forwards.It is marked by three longitudinal ridges.Another thick ridge adjoins the lateral border.This part of bone is almost rod like: IIt acts as a lever for the action of arm
2. The dorsal surface gives attachment to the spine of the scapula which divides the surface into a smaller supraspinous fossa and a larger infraspinous fossa.The two fossae are connected by the spinoglenoid notch,situated lateral to the root ofthe spine.

The costal or ventral surface of the scapula presents a broad concavity, the subscapular fossa.

It provides an attachment for the subscapularis muscle.
The supraspinatous fossa (supraspinatus fossa, supraspinous 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.

The Scapula

Overview

The scapula is a thin bone placed on the posterolateral aspect of the thoracic cage.The scapula has two surfaces ,three borders ,three angles,and three processes

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

The scapula forms the posterior part of the shoulder girdle. In humans, it is a flat bone, roughly triangular in shape, placed on a posterolateral aspect of the thoracic cage.

Ossification

What is it?:

Ossification is the process of bone formation, in which connective tissues, such as cartilage are turned to bone or bone-like tissue. The ossified tissue is invaginated with blood vessels. These blood vessels bring minerals like calcium and deposit it in the ossifying tissue. Bone formation is a dynamic process, with cells called osteoblasts depositing minerals, and osteoclasts removing bone.^[1] This process, termed bone remodeling continues throughout life.

The clavicle is first bone in the body to ossify. Except for its medial end ,it ossifies in membrane. It ossifies from two primary centries and one secondary centre.

The two primary centres appear in the shaft between the fifth and sixth weeks of intrauterine life, and fuse about the 45th day. The secondary centre for the medial end appears during 15-17 years ,and fuses wuth the shaft during 21-22 years. Occasionally tere may be a secondary centre for the acromial end.

ATTACHMENTS OF THE CLAVICLE

1. At the lateral end the margin of the articular surface for the acromioclavicular joint gives attachment to the joint capsule.
2. At the medial end the margin of the articular surface for the sternum gives attachment to : (a) The capsule all around : (b) the articular disc posterosuperiorly and (c) the interclavicular ligament superiorly.
3. Lateral one third of shaft: (a) The anterior border gives origin to the deltoid (b) The posterior border provides insertion to the trapezius (c) Conoid tubercle and trapezoid ridge give attachment to the conoid and trapezoid parts of the coracoclavicular ligament.

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4. Medial two thirds of the shaft :

(a) The anterior surface gives origin to the pectorallis major

(b) The rough superior surface gives origin to the clavicular head of the sternocleidomastoid.

(c) The oval impression on the inferior surface at the medial end gives attachment to the costoclavicular ligament.

(d) The subclavian groove gives insertion to the subclavus muscle. The margins of the groove give aatachment to the clavipectoral fascia.

 

Scapula and Clavicle

Sternoclavicular Joint

Images

Sex Determination

• In females, the clavicle is shorter , lighter  thinner , smoother , and less curved than in males.
• The mid shaft circumference and the wieght of the clavicle are reliable criteria

Clavicle Images

Acromioclavicular joint

Glenoid fossa of right side.

Peculiarities

1. It is the only long bone that lies horizontally
2. It is subcutaneous throughout .
3. It is the first bone to start ossifying.
4. It the only long bone which ossifies in membrane
5. It is occasionally pierced by the middle supraclavicular nerve.

Site Determination

The side to which clavicle belongs can be determined from the characters:

1. Lateral end is flat, and medial end is large and quadrilateral.
2. The shaft is slightly curved, so that it is convex forwards in its medial two -thirds, and concave forwards in it’s lateral one-third.
3. The interior surface is grooved longitudinally in it’s middle one -third.