Page 150 - Anatomy and Physiology of Farm Animals, 8th Edition

Anatomy of the Muscular System / 135

fourth digit; and in the horse, on the proxi­
mal phalanx of the third (and only) digit.
VetBooks.ir Flexors of the Digit. In all animals the

principal digital flexors are the superficial
and the deep digital flexor muscles. The
deep digital flexor m. (m. flexor digitorum
profundus) lies the closest to the meta­
carpal bones. It originates from the humerus,
radius, and ulna. Its long, stout tendon
extends distad through the carpal canal,
then along the palmar side of the metacarpus
to insert on the palmar surface of the distal
phalanges. As with the common digital
extensor tendon, the number of insertions
depends on the number of digits, with the
main tendon dividing into individual slips,
one per digit, just proximal to the fetlock.
The deep digital flexor is the only muscle
that flexes the distal interphalangeal joint.
Secondarily, it also flexes the more proximal
joints of the digit and the carpus. The
deep digital flexor m. also is important in
supporting the fetlock. Figure 7-9. Tenosynovitis (bowed tendon). Note
swelling on the palmar aspect above the fetlock in
The superficial digital flexor m. the area of the flexor tendons.
(m. flexor digitorum superficialis) is
similar to the deep digital flexor m., but it Muscles of the Pelvic Limb
inserts primarily on the proximal part of
the middle phalanx of each digit. In the
horse, the superficial digital flexor tendon See Figure 7‐10 and Table 7‐3 for an over­
inserts on the palmar aspects of the proxi­ view of muscles of the pelvic limb.
mal end of the middle phalanx and the Unlike the thoracic limb, the pelvic
distal end of the proximal phalanx. limb is joined to the axial skeleton by a
Tendons of both the superficial and deep synovial joint, the coxofemoral or hip
digital flexor mm. can be palpated palmar to joint. The hip is a ball‐and‐socket joint
and as such can move in nearly any direc­
the cannon bone. The expression bowed tion. However, in ungulates the chief
tendons describes a traumatic condition movements are extension and flexion.
of horses involving tendonitis of one or Lesser amounts of adduction, abduction,
both of these tendons in the cannon and some rotation are also possible. Joints
region (Fig. 7‐9). distal to the hip function primarily in the
Interosseous muscles lie between
the metacarpal bones of carnivores and sagittal plane, producing mostly flexion
humans. In large ungulates most of the and extension.
muscle tissue has been replaced with
connective tissue, and these structures are Muscles Acting on the Hip Joint
known as the suspensory ligaments. They
take origin from the palmar aspect of the Extensors of the Hip. The chief extensors
proximal metacarpus and insert on the of the hip are the so‐called hamstring
proximal sesamoid bones. The suspensory muscles, which pass caudal to the hip
ligaments are part of the passive support of from the pelvis to the proximal end of the
the metacarpophalangeal joint. tibia, fibula, or calcaneus of the tarsus.