Page 99 - Anatomy and Physiology of Farm Animals, 8th Edition

84 / Anatomy and Physiology of Farm Animals

VetBooks.ir

a
g
h
b i
c
j
d e
f k
l
m

Figure 4-11. Some bony landmarks palpable on the horse. a, scapular spine and tubercle; b, greater
tubercle of the humerus; c, deltoid tuberosity of the humerus; d, lateral epicondyle of the humerus; e,
olecranon process of the ulna; f, accessory carpal bone; g, tuber coxae; h, greater trochanter of the
femur; i, third trochanter of the femur; j, patella; k, tibial tuberosity; l, calcaneal tuber; m, lateral
epicondyle of the tibia.

extremities. The proximal end bears a forms a lever for attachment of the muscles
rounded, articular head that participates that extend the elbow. In the horse, the
with the ventral angle of the scapula to proximal portion of the shaft of the ulna is
form the scapulohumeral (shoulder) well developed but fused to the radius; the
joint. The proximal end of the humerus distal ulna is absent. The ox, sheep, goat,
also features a number of irregular tuber- and pig each have a complete ulna, but
osities and tubercles, providing sites of with little or no movement between the
attachment to muscles of the shoulder ulna and radius. The cat and dog have con-
region. The palpable prominence pro- siderably more movement between these
duced by this end of the humerus is called complete bones, but not nearly as much as
the point of the shoulder. The distal end of primates, who can pronate and supinate
the humerus forms a spool‐like condyle their hands through the rotation of radius
that articulates with the proximal ends of and ulna relative to one another.
the radius and ulna in the elbow. The carpus in all animals is a complex
The radius and ulna are the bones of region that includes two rows of small
the antebrachium (forearm). In mam- bones (Fig. 4‐13). This region corresponds
mals, the radius is the larger of the two, to the human wrist, and is frequently,
although in birds it is smaller than the ulna. although erroneously, called the “knee” by
The radius enters into the elbow joint horsemen (the true knee is the stifle joint).
proximally and the carpus distally. The Carpal bones in the proximal row are
radius can be felt directly beneath the skin called (from medial to lateral) radial,
on the medial side of the forearm. intermediate, and ulnar, whereas those in
The ulna varies in its degree of develop- the distal row are numbered 1 to 4 from
ment from species to species. The promi- medial to lateral. In addition, an accessory
nent olecranon process (point of the carpal bone projects caudad from the lat-
elbow) is found in all mammals proximal eral side of the carpus. The numbering of
and caudal to the elbow joint. This process the carpal bones of the distal row is based