Page 169 - Anatomy and Physiology of Farm Animals, 8th Edition

154 / Anatomy and Physiology of Farm Animals

he foot of the horse is a highly modi- ceous) covering of the distal part of the
The hoof is the cornified (keratina-
Tfied single digit, adapted for great
VetBooks.ir speed in grasslands. The structures from digit. This chapter integrates the detailed
gross anatomy of the hoof with the other
the carpus (which lay people frequently call
the knee) and distal in the thoracic limb components of the foot, and describes the
correspond to the wrist and hand of humans specialized ligamentous apparatus (stay
(Fig. 8‐1). These structures constitute the apparatus and reciprocal apparatus) char-
manus, and an examination of the bony acteristic of the limbs of Equidae.
components will reveal the same basic plan
for both species: two horizontal rows of
carpal bones, a single fully formed meta- Structure of the Foot
carpal bone for each digit (of which there is
only one in the horse), and three phalanges Bones and Cartilages
within each digit. Likewise, the hock and
more distal structures in the equine pelvic Anatomy of the carpus and tarsus are
limb are homologous to the ankle and foot discussed in Chapters 4 and 6. In the
of humans; these constitute the pes. From thoracic limb, the large metacarpal III
the cannon bone distad, the equine manus (cannon bone) and the smaller medial (II)
and pes are nearly identical, except in a few and lateral (IV) metacarpal bones (splints)
details of blood supply and innervation. articulate proximally with the carpus; the
Among domestic horses, most lameness is cannon bone articulates distally with the
referable to the foot (and most of these are proximal phalanx and two proximal sesa-
associated with the forefoot, which bears moid bones. Similarly, in the pelvic limb
more weight than the hindfoot). metatarsals II to IV articulate proximally

Manus
Pes

Figure 8-1. Comparative anatomy of human and equine limbs. In the thoracic limb, the manus com-
prises the carpus and elements more distal (corresponding to the human wrist and hand). In the pelvic
limb, the pes includes the tarsus and elements more distal (the human ankle and foot). The horse there-
fore stands on a single digit, homologous to the middle human finger or toe.