Biomedical Engineering Reference
In-Depth Information
particular modes of locomotion, use a functional division
between digits II and III (e.g. Alouatta).
general pattern in all mammals. The names for nerves in
nonhuman primates are the same as those in humans.
The nerves of the hindlimb are usually derived from
ventral rami of spinal nerves from all lumbar segments as
well as the first two sacral segments. Despite the fact that
the number of segments in these two regions varies
considerably between nonhuman primates and humans, the
basic pattern for the development of the lumbosacral plexus
and the final distribution of the peripheral nerves does not
differ. The number of actual nerves contributing to the
plexus is usually the same in all the species. The position of
the nerves as they course through the hindlimb follow the
same general pattern in all mammals. As in the forelimb,
the names of the nerves in nonhuman primates are the same
as those in humans where the nomenclature may differ
from those used in other animals.
The blood supply to the forelimbs and hindlimbs of
nonhuman primates (
Lineback, 1933b
) is the same as in
humans and other animals. The primary source of blood for
the forelimb is the axillary artery and for the hindlimb the
external iliac artery. The course of the vessels in the limbs
resembles that of humans as well as other mammals.
Particularly because of the similarities in the hands and
feet, the descriptions of the vascular supply of humans are
applicable to nonhuman primates.
Musculature of Hindlimb
The muscles of the hindlimb are similar to those of other
mammals and humans. The names commonly used for
identifying muscles in nonhuman primates, however, are
the same as those used for humans rather than most other
mammals. For example, the three glutei muscles are called
mm. gluteus maximus, g. medius, and g. minimus in both
human and nonhuman primates rather than mm. gluteus
superficialis, g. medius, and g. profundus as in most
mammals. Despite the use of the same terminology, the
orientation of the muscles in nonhuman primates, particu-
larly in the proximal part of the limb, differs from that of
humans because of the latter's unique adaptation to
bipedalism. In each species hindlimb musculature is
reflective of the species' specific use of the limb in a variety
of locomotor and postural behaviors. (See
Howell and
Straus (1933a)
or
Stern (1971)
for detailed descriptions of
the muscles.)
Like the hand, the foot of nonhuman primates has
considerable dexterity and its grasping capabilities are well
developed, particularly in more arboreal species. In the foot
both the extrinsic and intrinsic muscles are well developed
and, as in the hand, the fibers for each individual digit are
usually clearly distinguishable although considerable
minor variations are seen between different taxa. The same
four layers of intrinsic muscles seen on the palmar surface
of the hand appear on the plantar surface of the foot. The
size of the eminences, which are the equivalent of the
thenar and hypothenar eminences in the hand, differs
greatly among species and can be correlated to gait as well
as habitat use. The big toe (hallux) of all nonhuman higher
primates is divergent from the other four digits and as such
its musculature is generally well developed. The length and
robustness of the big toe (digit I) vary greatly among
species. In general, differences between the hand and foot
are in the degree of development or independence of the
digits with the exception that, unlike the hand, the foot has
intrinsic extensor muscles on its dorsum.
Clinically Significant Features of Limb
Morphology
Clinically significant features of limb morphology in
nonhuman primates include awareness of multiple uses
of the extremities, locations for venepuncture and
peripheral nerve biopsy, and schedule of epiphyseal
fusion of the long bones as a means of aging immature
animals (see the section “Dental and skeletal matura-
tion” above).
The extremities of nonhuman primates are morpho-
logically and functionally more similar to human limbs
than to other animals. For this reason topics on human
orthopedics and surgical anatomy are better guides than
those routinely used in veterinary practice. One of the
most important concepts regarding primate extremities is
that they are not unipurpose. They have therefore retained
a generalized form to enable the animal to manifest a wide
range of behaviors. In addition to large ranges of motion
in the anterior
Neurovascular Systems of Limbs
The nerves of the forelimb (
Howell and Straus, 1933b;
Swindler and Wood, 1973
) are usually derived from the
ventral rami of spinal nerves C5, C6, C7, C8, and T1. The
basic pattern for the development of the brachial plexus and
the final distribution of the peripheral nerves is laid down
early in embryologic development and is the same in all
primates both nonhuman and human. The position of the
nerves as they course through the forelimb follows the same
posterior plane both extremities also have
considerable mobility in other planes. The forelimb
(upper) in particular can usually be markedly abducted as
well as longitudinally rotated since the well-developed
clavicle maintains the limb in its lateral position on the
dorsoventrally flattened thorax. The supination and
pronation of the forearm and the dexterity of the hand add
yet other dimensions to mobility for locomotion, feeding,
e
