Human Anatomy - Zynoviy Myrchuk, Maryna Myrchuk 2007

Axial Skeleton
Bones of the Upper Limb

The Pectoral Girdle consists of two bones: the scapula and the clavicle.

The scapula is a paired, flat, triangular bone located on the posterior surface of the Thorax at the level of the 2nd to 7th Ribs. It presents anterior (concave) costal and posterior (convex) dorsal surfaces, as well as three angles: inferior, lateral, and superior. The depression on the costal surface of the scapula is called the subscapular fossa. The dorsal surface features a well-developed and posteriorly prominent bony ridge—the spine of the scapula—which continues into a broad, flat process known as the acromion. Through the acromion, the scapula articulates with the clavicle. The scapular spine separates the supraspinous fossa above from the infraspinous fossa below.

The lateral angle of the scapula is thickened and flattened, forming the glenoid cavity for articulation with the HEAD of the humerus. The scapular neck lies just behind the glenoid cavity. From the superior margin of the scapula (near its neck), a well-defined coracoid process projects upward.

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Fig. 4. Pectoral girdle

Fig. 5. Skeleton of the Upper Limb

The clavicle is a paired, long, tubular, S-shaped bone positioned nearly horizontally between the clavicular notch of the Sternum and the acromion, situated anteriorly and superiorly to the first rib. The clavicle is easily palpable beneath the Skin. It consists of a body (its central portion) and two extremities: the sternal and acromial ends. The sternal end articulates with the sternum, while the acromial end articulates with the scapula.

The skeleton of the free upper limb (Fig. 6) comprises the humerus, the BONES OF THE forearm (ulna and radius), and the hand, which in turn includes the Carpal Bones, Metacarpal bones, and Phalanges of the fingers.

The carpus consists of 8 small bones arranged in two rows of four. In the proximal row, from lateral to medial, are the scaphoid, lunate, triquetrum, and pisiform bones. The distal row is formed by the trapezium, trapezoid, capitate, and hamate bones.

The metacarpus consists of 5 short tubular bones—the metacarpals. They are numbered from the thumb to the little finger. Each metacarpal has a base (proximal end), a body (shaft), and a head (distal end).

Bones of the digits (fingers). The hand comprises the thumb, index finger, middle finger, ring finger, and little finger. There are 14 phalanges in total. The thumb consists of two phalanges, while the remaining four digits have three each: proximal, middle, and distal. These are short tubular bones featuring a base, body, and head.

The humerus is a typical long tubular bone. It comprises a body (the central shaft, or diaphysis) and two extremities (epiphyses): proximal and distal. The proximal end articulates the humerus with the scapula, while the distal end articulates with the forearm bones. The proximal end forms the humeral head, a portion of which can be palpated through the skin deep within the axillary fossa.

The distal end of the humerus is widened, slightly curved anteriorly, and terminates in the humeral condyle. Two prominences—the medial and lateral epicondyles—are visible on the medial and lateral sides above the condyle, serving as Muscle attachment sites. Each epicondyle is easily palpable beneath the skin. The medial part of the condyle is pulley-shaped (trochlea) and articulates with the ulna. Adjacent to the trochlea is the ball-shaped capitulum of the humerus, which articulates with the radius.

The ulna is located on the side of the little finger (digit 5), whereas the radius is on the side of the thumb (digit 1).

The proximal end of the ulna is thickened and features a trochlear notch bordered by the coronoid (anterior) and olecranon (posterior) processes. Through this notch, the ulna articulates with the trochlea of the humerus. The brachialis muscle attaches to the ulnar tuberosity located just below the coronoid process. The distal end of the ulna bears a head, from which a styloid process projects medially.

Fig. 6. Skeleton of the free upper limb

The proximal end of the radius features a cylindrical radial head with an articular fossa for articulation with the capitulum of the humerus. Below the head lie the neck and the radial tuberosity, to which the biceps brachii muscle attaches. The distal end of the radius is thickened. Its lateral side bears a styloid process, while its medial side features the ulnar notch for articulation with the head of the ulna. The radius articulates with the proximal row of carpal bones via the carpal articular surface of the upper limb.