20 Systems Anatomy

FIGURE 1.11. Right humerus, posterior aspect.

1 Skeletal Anatomy 21

FIGURE 1.12. Right humerus, anterior aspect.

22 Systems Anatomy

FIGURE 1.13. A: Right humerus, anterior aspect, showing muscle origins and insertions. B: Right

humerus, posterior aspect, showing muscle origins (red) and insertions (blue).

A B

Shaft of the Humerus

The shaft of the humerus, also anatomically referred to as

the body, spans the portion of the humerus from the surgical neck proximally and to the area just proximal to the portion referred to as the distal extremity (see Figs. 1.11 to

1.13). (The distal extremity includes the condyles, capitulum, and trochlea, as discussed later.) The shaft of the

humerus is cylindrical in the proximal portion, but

becomes progressively flatter and somewhat triangular distally. In the distal portion of the shaft, the bone actually has

three surfaces, but two borders (the medial and lateral borders).

The surfaces of the shaft of the humerus consist of an

anterolateral surface, an anteromedial surface, and a posterior (or dorsal) surface. The anterior surface is divided into

the anterolateral and anteromedial surfaces by an oblique

ridge that starts proximally and laterally at the greater

tuberosity and extends distally to end near the medial epicondyle.

The anterolateral surface of the proximal humeral shaft

provides the elongated insertion area of the pectoralis major

muscle, which attaches along the distal part of the crest of

the greater tuberosity (see earlier, under The Proximal End

of the Humerus). Lateral and distal to the insertion of the

pectoralis major is an oblong area that provides the insertion point of the deltoid muscle. This area, known as the

deltoid tuberosity, is located on the anterolateral surface of

the humerus and consists of a raised, slightly triangular elevation. Distal and anterior to the deltoid tuberosity, extending along the anterolateral surface of the humeral shaft,

there is a relatively large, broad, slightly concave area that

provides the origin area for the brachialis. Also distal to the

deltoid tuberosity is the radial sulcus (radial groove), which

extends obliquely distally, spiraling along the lateral shaft,

and provides the path for the radial nerve and profunda

brachii artery (see Figs. 1.11 and 1.13B). The radial sulcus

is bordered on one side by the origin of the lateral head of

the triceps, the deltoid tuberosity, and the origin of the

brachialis (all located lateral and proximal to the groove).

On the other side of the radial sulcus is the origin of the

medial head of the triceps, located medial and distal to the

sulcus.