Human Anatomy - Kotsan I. Y. 2009

Skeleton of the Upper Limb
Bones of the Free Upper Limb

The BONES OF THE free upper limb include the humerus, the bones of the forearm, and the bones of the hand.

The humerus is a long tubular bone comprising a central shaft (diaphysis) and two extremities, proximal and distal (Fig. 53).

Class="center">

Fig. 53. Right humerus

I — anterior view, 1 — anatomical neck, 2 — HEAD of the humerus, 3 — crest of the lesser tubercle, 4 — surgical neck, 5 — nutrient foramen, 6 — medial border, 7 — medial anterior surface, 8 — coronoid fossa, 9 — medial epicondyle, 10 — trochlea, 11 — capitulum of the humerus (head of the condyle), 12 — lateral epicondyle, 13 — radial fossa, 14 — lateral anterior surface, 15 — lateral border, 16 — deltoid tuberosity, 17 — crest of the greater tubercle, 18 — intertubercular sulcus, 19 — lesser tubercle, 20 — greater tubercle; II — posterior view: 1 — head of the humerus, 2 — anatomical neck, 3 — greater tubercle, 4 — surgical neck, 5 — groove for the radial nerve, 6 — posterior surface, 7 — olecranon fossa, 8 — lateral epicondyle, 9 — trochlea, 10 — groove for the ulnar nerve, 11 — medial epicondyle

The shaft of the humerus (corpus humeri) is slightly twisted along its axis. In its upper section, it is cylindrical, becoming triangular toward the lower end. The lower section of the shaft presents a posterior surface (facies posterior), a medial anterior surface (facies anterior medialis), and a lateral anterior surface (facies anterior lateralis). The anterior and posterior surfaces are separated by the medial border (margo medialis) and lateral border (margo lateralis). Slightly above the middle of the bone shaft on its lateral anterior surface lies the deltoid tuberosity (tuberositas deltoidea), where the deltoid Muscle attaches. Below the deltoid tuberosity, the radial nerve groove (sulcus nervi radialis) spirals across the posterior surface of the bone shaft.

The proximal end of the humerus is thickened and features the spherical head of the humerus (caput humeri), which faces medially, upward, and slightly backward. A shallow circular groove, the anatomical neck (collum anatomicum), encircles the periphery of the head. Immediately distal to the anatomical neck are two tubercles: the lesser tubercle (tuberculum minus) anteriorly, and the greater tubercle (tuberculum majus) laterally, which features three facets for muscle attachment. Extending downward from each tubercle are the crest of the lesser tubercle (crista tuberculi minoris) and the crest of the greater tubercle (crista tuberculi majoris). Between the two tubercles and their crests lies the intertubercular sulcus (sulcus intertubercularis), through which the tendon of the long head of the biceps brachii passes. Below the tubercles, at the junction of the proximal end and the shaft, lies a slight constriction known as the surgical neck (collum chirurgicum). This is the most common site for fractures of the humerus.

The distal end of the humerus is flattened, widened, and slightly curved forward, terminating in the humeral condyle (condylus humeri). The medial part of the condyle forms the trochlea of the humerus (trochlea humeri) for articulation with the ulna of the forearm. Lateral to the trochlea lies the capitulum of the humerus (capitulum humeri) for articulation with the radius. Anteriorly, just above the capitulum, is the radial fossa (fossa radialis), while two deep fossae are located above the trochlea: the coronoid fossa (fossa coronoidea) anteriorly, and the olecranon fossa (fossa olecrani) posteriorly, which accommodate the processes of the ulna during flexion and extension of the forearm. The medial and lateral epicondyles are situated on the medial and lateral sides above the humeral condyle. The medial epicondyle (epicondylus medialis) is more pronounced. Its posterior surface features the ulnar nerve groove (sulcus nervi ulnaris). Superiorly, this epicondyle continues into the medial supracondylar ridge (crista supracondylaris medialis), which forms the medial border (margo medialis) along the humeral shaft. The lateral epicondyle (epicondylus lateralis) is smaller than the medial one and extends upward into the lateral supracondylar ridge (crista supracondylaris lateralis), which forms the lateral border (margo lateralis) of the shaft.