Bones of Upper Limb

Bones of Upper Limb

• The upper limb consists of 64 bones, divided into two parts: the bones of the pectoral girdle and the bones of the free upper limb.
• The pectoral girdle is composed of the clavicle and scapula, which connect the free upper limb bones to the trunk.

Clavicle

• The clavicle is approximately 15-17 cm long and 2-3 cm wide, and has the shape of a horizontal letter "S" on the front of the shoulder and thorax.
• It articulates with the sternum on the inside and the scapula on the outside, connecting the upper extremity to the trunk.
• The clavicle has superior and inferior surfaces, anterior and posterior borders, and sternal and acromial ends.
• The acromial end features a small oval acromial facet for articulation with the scapula.
• The inferior surface of the lateral third of the clavicle has a prominent conoid tubercle and a trapezoid tubercle (line), serving as attachment sites for the coracoclavicular ligament.
• The inferior surface of the medial third of the clavicle has an impression for the costoclavicular ligament.
• Clavicle fractures are common, especially in individuals with less fat in that area, and can result from falls onto the shoulder, direct trauma, or an outstretched arm.

Scapula

• The scapula is a flat, triangular bone located at the 2nd to 7th levels of the ribs, connecting the clavicle to the humerus.
• It has two faces: the costal surface (anterior) and the posterior surface, and three borders: the superior, medial, and lateral borders.
• The scapula has three angles: the superior, inferior, and lateral angles.
• The posterior surface of the scapula is convex and features a protrusion called the spine of scapula, which divides into two concave surfaces: the supraspinous fossa and the infraspinous fossa.
• The deltoid and trapezius muscles attach to the spine of the scapula.
• The superior border of the scapula is the shortest and thinnest, displaying a slight concave shape, and includes a suprascapular notch.
• The lateral border of the scapula is strong and thick, situated closest to the axilla.
• The medial border is the long, medial edge of the scapula closest to the vertebral column.
• The superior angle is formed by the junction of the superior and medial borders, while the inferior angle is formed by the junction of the medial and lateral borders.
• The lateral angle is formed by the junction of the superior and lateral borders and contains the head and neck of scapula.
• The glenoid cavity is a shallow pit on the lateral margin of the scapula's head, forming the glenohumeral joint with the head of the humerus.
• The supraglenoid tubercle is a small ridge above the glenoid cavity, where the long head of the biceps brachii muscle attaches.
• The infraglenoid tubercle is a roughened area below the glenoid cavity, where the long head of the triceps brachii muscle attaches.
• The acromion is the broad, straight lateral extension of the spine of scapula, articulating with the clavicle at the acromioclavicular joint.
• The coracoid process is a thick, beak-like structure that projects anterolaterally from the lateral end of the scapula.