Biomedical Engineering Reference
In-Depth Information
expression of local insulin-like growth factor-I receptors
(IGF-IR) in growth plates that dictate the amount of
longitudinal growth in a given end of a long bone, resulting
in distinctive species-specific patterns of limb propor-
tioning (
Serrat et al., 2007
). Vertical clingers and leapers
generally have low intermembral indices (50
be well adapted to its particular habitat use yet similar
characteristics may be manifest in species with very
different patterns of behavior. For example, in three genera
external thumbs are either severely reduced or absent
although some of the internal morphology may be main-
tained. One of these, Colobus, is an Old World monkey
which locomotes quadrupedally but exhibits a pattern of
leaping and landing behavior in its locomotor repertoire
which
Morbeck (1976)
related to its significantly reduced
thumb. The other two, Ateles and Brachyteles, are
prehensile-tailed New World monkeys which make exten-
sive use of suspensory locomotion. Other external modifi-
cations of the hands and feet of New World monkeys are
found among the Callitrichidae. Unlike all other higher
primates, Callitrichidae possess nails only on their big toes
(halluces) while the rest of their distal phalanges have
claws (see the description of nails and claws in the section
“Nails or claws” above). Both palmigrade/plantigrade and
digitigrade locomotion are utilized by primates (
Patel,
2009
). The repertoire of some apes also includes walking
with the dorsum of the phalanges of digits II to V in contact
with the substrate either as knuckle walking (middle
phalanges) or fist walking (proximal phalanges with or
without concurrent thumb contact) (
Tuttle, 1967
).
In addition to locomotion the primate hand, and
sometimes also the foot, is routinely used in other impor-
tant aspects of the behavioral repertoire, e.g. feeding, social
grooming, and sexual behavior. Its functional morphology
thus reflects not only locomotor skills but also such things
as dexterity in food acquisition. Although not studied
extensively, some nonhuman primates display handedness
(
Ward and Hopkins, 1993
). Individual rhesus macaques
preferentially use one hand, but the study population as
a whole was not predominantly left or right handed
(
Rawlins, 1993
). Cebus apella appear to be primarily
right handed (
Christel and Fragaszy, 2000
) while Cebus
albifrons exhibit differences in preferences by task (
West-
ergaard et al., 1999
). Although evidence suggests that
chimpanzees prefer the right hand, preference may change
with task (
Hopkins et al., 2009
) which is similar to recent
findings in orang-utans (
Peters and Rogers, 2008
).
80), indi-
cating short forelimbs and long hindlimbs. Both terrestrial
and arboreal quadrupeds generally have midrange inter-
membral indices (80
e
100) with forelimbs and hindlimbs
approximately equal. Brachiators or species who use
suspensory locomotion extensively usually have long
forelimbs and short hindlimbs and high intermembral
indices (100
e
150). These criteria are indicators of func-
tional morphology but species variation does not always
exactly follow these rules.
Externally all primate limbs appear to be similar, but
each species has its own unique modifications. All New
World monkeys are basically arboreal and some of the
species have prehensile tails that can be used as a fifth
appendage (see the description of the tail in the sections
“Overview of back and tail” and “Skeleton” under back and
spine morphology above). Old World monkey limb
morphology generally follows one of two patterns, and
reflects whether the animals are primarily arboreal or
terrestrial. Both lesser and great apes generally have long
forelimbs relative to either their trunks or hindlimbs. All
have morphology that is consistent with brachiators even
though this mode of locomotion is not usually used by
larger, heavier adults.
The hands and feet of all higher primates have marked
prehensibility, i.e. all the digits can converge during flexion
and diverge during extension (
Figures 4.3,4.4
). Except in
Callitrichidae, the thumbs (pollices) and big toes (halluces)
of all higher nonhuman primates are divergent and func-
tionally opposable, i.e. the palmar surface of the distal
segment of the thumb or big toe can be placed parallel and
opposite the equivalent part of one or more of the other
digits. The hands of Colobus, Ateles, and Brachyteles are
exceptions to this in that they lack functional thumbs. Old
World monkeys and apes have true opposability of the
thumb since the carpometacarpal joint allows longitudinal
rotation of the first metacarpal. Cebidae New World
monkeys have pseudo-opposability of the thumb because
the carpometacarpal joints of these species do not allow
longitudinal rotation of the first metacarpal. The big toes of
all higher nonhuman primates are divergent and pseudo-
opposable lacking longitudinal rotation in their tarso-
metatarsal joints. Quadrupedal locomotion includes both
digitigrade and palmigrade/plantigrade positions and both
may be used in a single locomotor sequence (
Schmitt and
Larson, 1995; Patel, 2009
).
The length, both relative and numerically, of individual
digits on the hands and feet show considerable variation
among species. The pattern seen in each species appears to
e
Skeleton of Forelimb
Like the muscles, the bones of the extremities of nonhuman
primates follow the mammalian pattern in general and
humans in particular (
Sullivan, 1933
). The girdles, partic-
ularly the pectoral girdle, show some modification from the
generalized mammalian pattern but are fairly consistent
within primates. The proximal segment of each limb
always has one bony element, the more distal segment has
two discrete bony elements, the carpus has nine (or eight)
and the tarsus seven short irregular bones; the metacarpus
and metatarsus each have five long bones per extremity, and
