Human Anatomy, Part 1 - K. A. Dyubenko, A. K. Kolomiyytsev, Yu. B. Chaykovsky 2002

Special Part
Appendicular Skeleton, skeleton appendiculare — Bones of the Upper Limb, ossa membri superioris
Free Part of the Upper Limb, pars libera membri superioris — Humerus

The Free part of the upper limb, *pars libera membri superioris*, consists of three segments:

1) the arm, *brachium*, the Skeleton of which is formed by the humerus;

2) the forearm, *antebrachium*, the skeleton of which is formed by the forearm bones (radius and ulna);

3) the hand, *manus*, the skeleton of which is formed by the Carpal Bones, Metacarpal bones, and Phalanges of the fingers.

The hand is the distal segment of the upper limb, performing complex motor and sensory Functions.

The humerus, *os humerus*, is a long tubular bone comprising a body, *corpus humeri*, and two extremities: an upper (cylindrical) and a lower (triangular) (Fig. 63). The lower part of the body features a posterior, anteromedial, and anterolateral surface, as well as medial and lateral borders. On the anterolateral surface of the body, slightly above its center, lies the deltoid tuberosity, *tuberositas deltoidea*. The radial groove, *sulcus n. radialis*, runs along the posterior surface of the humeral body. The upper end of the bone bears the HEAD of the humerus, *caput humeri*. The head is separated from the rest of the bone by a narrow groove known as the anatomical neck, *collum anatomicum*. Below the anatomical neck on the anterolateral surface are the greater tubercle, *tuberculum majus*, and the lesser tubercle, *tuberculum minus*. Inferiorly, these tubercles continue into corresponding crests, *crista tuberculi majoris et minoris*. Between these crests lies the intertubercular groove, *sulcus intertubercularis*, which lodges the tendon of the long head of the biceps brachii. At the junction of the upper extremity and the body lies a narrowing of the bone known as the surgical neck, *collum chirurgicum*, which is a frequent site of fractures.

At the lower end of the humerus, laterally, lies a spherical articular eminence—the capitulum of the humerus, *capitulum humeri*—next to which is located the trochlea of the humerus, *trochlea humeri*.

Class="center">

Fig. 63. Humerus, *os humerus*: A - anterior view; B - posterior view

On the anterior surface of the lower extremity, superior to the trochlea, is the coronoid fossa, *fossa coronoidea*, and superior to the capitulum is the radial fossa, *fossa radialis*; on the posterior surface above the trochlea lies the olecranon fossa, *fossa olecranii*. The condyle of the humerus, *condylus humeri*, is triangular in shape with its base directed inferiorly. It features two epicondyles: the medial epicondyle, *epicondylus medialis*, and the lateral epicondyle, *epicondylus lateralis*. The groove for the ulnar nerve, *sulcus n. ulnaris*, runs along the posterior surface of the medial epicondyle.

Ossification. In newborns, the upper and lower extremities of the humerus are cartilaginous. The ossification center in the head appears During the first year of life, in the greater tubercle at 2–3 years, and in the lesser tubercle at 3–5 years. All nuclei of the proximal epiphysis of the humerus fuse by 12–16 years of age. Nuclei in the distal epiphysis appear in the following sequence: in the capitulum at 1–3 years, in the medial epicondyle at 5–7 years, and in the trochlea at 8–12 years of life.