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Chapter 5

The Wing: Normal Gross Anatomy

coracoideus tendon to its point of attachment on the
III TERMINOLOGY: HUMERAL JOINT OR upper edge of the humeral tubercle (Figure 5-3).
SHOULDER GIRDLE?

It is my studied opinion that the term shoulder girdle, III HUMERUS
as used by some authorities to describe the scapula,

coracoid, and clavicle of birds, is misleading because When extended for flight and viewed from above, the
it suggests functional independence from the humerus, humeral shaft appears gracefully recurved, convex
which is not the case. It is my view that all four bones along its upper half, and concave along its lower
that form the humeral joint and its medial support— portion (Figure 5-4). Distally, the humeral metaphysis

the clavicle—should be considered a single functional flares abruptly, forming the humeral condyle, which is
unit (or dysfunctional unit, in the case of injury). composed of lateral and medial halves to accommo-
date the articular portions of the ulna and radius,
respectively (Figure 5-5).
III HUMERAL JOINT
The humeral joint (shoulder) of a bird comprises four III CUBITAL JOINT
bones: the humerus, scapula, coracoid, and clavicle.
The scapula and coracoid form a common glenoid, The avian cubital joint, or elbow, is conceptually similar
which is supported medially by the clavicle. The prin- to the elbow of a mammal but differs markedly with
cipal articular element, the humeral head, is com- respect to the relative sizes of the radius and ulna
pressed laterally, unlike its mammalian counterpart. (Figures 5-6 and 5-7), which in a bird are just the oppo-
Viewed from below with the wing extended (Figure site of those of a dog, for example. The avian olecranon
5-1), the disklike humeral head appears nearly end-on, is also much different than its mammalian counterpart
barely perceptible, and snugged in between the large because it is short and broad rather than tall and
blocky humeral tubercle and the proximal portions of narrow (Figure 5-8).
the coracoid and scapula, which together form the
glenoid.
Seen from in front with the wing extended (the III RADIUS AND ULNA
leading edge or hanging drop view), the proximal
humerus resembles the blade of a shovel topped by its The physical relationship between the radial and ulna
three appendages: the clavicle, coracoid, and scapula bodies somewhat resembles that of an unstrung bow,
(Figure 5-2). the ulna being gently arched and the radius nearly
straight (Figure 5-9). The radius and ulna of most birds
are about 15% longer than the humerus. Distally, the
III TRIOSSEAL CANAL radial epiphysis resembles a knob, extending well
beyond the adjacent ulna. For its part, the lateral aspect

The triosseal canal is formed by the confluence of three of the ulnar epiphysis looks like a blunted spade affi xed
of the four shoulder bones: the scapula, coracoid, and to a facet in the inner side of the radius (Figure 5-10).
clavicle. The canal transmits the fl ight-critical supra- Text continued on p. 63.
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