Page 123 - Anatomy and Physiology of Farm Animals, 8th Edition

108 / Anatomy and Physiology of Farm Animals

This fibrocartilage has a soft center, the sides of an intervertebral space are linked
by an intercapital ligament, which forms
nucleus pulposus, which may abnormally
VetBooks.ir protrude through the surrounding annulus a reinforcing band across the dorsal side of
the intervertebral disk. The presence of
fibrosus into the vertebral canal. The
resulting condition, a ruptured interverte- the intercapital ligament contributes to
bral disk, may cause significant injury to the rarity of dorsal disk protrusions in the
the overlying spinal cord. thoracic region of the vertebral column.
The articular processes of adjacent ver-
tebrae have flat surfaces that are apposed
to form plane joints with limited gliding Joints of the Appendicular
movements. These surfaces are larger and Skeleton
the movements more extensive near the
head, decrease in the thoracic region, and Joints of the Thoracic Limb
are again more extensive in the lumbar
region. The joints between sacral vertebrae The scapula has no true bony connection
fuse completely, and the sacrum becomes a with the thorax. It is held in place by a num-
single bone with the segments joined by ber of muscles and ligaments. This type of
synostoses. joint is sometimes called a synsarcosis.
The ribs are attached to the vertebral The shoulder (scapulohumeral) joint is
column by two separate joints (Fig. 6‐6). spheroid. Movements in all directions,
One is between the head of the rib and the including rotation, are possible. In domestic
cup‐like depression (fovea) formed by the animals, however, the arrangement of
bodies of two adjacent thoracic vertebrae; shoulder muscles practically limits move-
the other is between the tubercle of the rib ment to a hinge type of action in the sagittal
and a facet on the transverse process of the plane. Thus, extension and flexion are the
vertebra of the same number as the rib. chief movements. The head of the humerus
The heads of the paired ribs on opposite is a large sphere much more extensive than
the comparable cavity of the scapula. The
joint capsule is extensive, with poorly devel-
oped collateral ligaments. Instead, the ten-
dons of the muscles crossing the shoulder
joint on all sides act effectively as supportive
ligaments. (It is these well‐developed ten-
dons that blend in human beings to form
the so‐called “rotator cuff.” This term is not
used in veterinary anatomy, however.)
The elbow is a true ginglymus joint
formed by the humeral condyle meeting the
proximal ends of the radius and ulna. The
proximal end of the radius is slightly concave
and expanded to give an extensive surface
Figure 6-6. Costovertebral articulations. Cranial for support. Combined with the semilunar
is to the right; shown are the articulations between notch of the ulna, the radius forms a half‐
the proximal part of a rib (blue) and two adjacent circle embracing the humeral condyle. In
vertebrae (green and red). The head of the rib ungulates (hooved animals), movement in
articulates with the bodies of two adjacent verte-
brae at costal foveae (purple and red arrows). The the elbow is limited to flexion and extension.
tubercle of the rib articulates with the transverse In humans and to a lesser degree in carni-
process of the more caudal vertebra (blue arrow). vores, the joint between the radius and ulna
Both these joints are synovial in nature. The permits supination and pronation.
intervertebral disk, a specialized symphyseal joint, The carpus (Figs. 4‐12, 6‐7, and 6‐8) is a
is indicated in yellow. complex joint that permits flexion and