Biomedical Engineering Reference
In-Depth Information
FIGURE 4.4
Morphology of the right foot of Macaca mulatta. (A)
Plantar surface; (B) dorsal view of the skeletal elements. Note the presence
of a single plantar pad with creases and dermatoglyphs. As in the hand, the
major creases reflect the functional divisions of the digits, the nails on the
digits are visible from the plantar (volar) view, and, in the skeleton, there is
a marked separation between the first and second metatarsals. (Drawings
by Nancy Hong.)
FIGURE 4.5
External ear configuration in Old World versus New
World monkeys. (A) Old World monkey (Macaca mulatta); (B) New
World monkey (Cebus apella). Note the lateral bony extension in the Old
World monkey contributing to the formation of an external auditory tube.
In the NewWorld monkey the tympanic ring for the tympanic membrane is
on the surface of the skull and the ear ossicles are clearly visible. In both
the temporomandibular articulation is immediately anterior to the opening.
(Drawings by Nancy Hong.)
Coleman and Ross, 2004
). The pinna is generally immobile
in higher primates, and Old World monkeys have muscles
for only retraction of the ears. In Pan, three auricular
muscles are present but greatly reduced in size, as in
humans, and produce only trivial movements of the auricle
relative to the scalp (
Burrows et al., 2006
). The external ear
is covered by hair which varies in density between species
and may form an ear tuft on the superior point of the pinna.
The external auditory tube lies between the external
opening of the ear and the tympanic membrane. The
structure of this tube varies along evolutionary lines. In Old
World monkeys and apes the bony tympanic ring is elon-
gated laterally so the medial portion of the external audi-
tory tube is bone rather than cartilage. NewWorld monkeys
lack this prolongation so the tympanic ring is exposed on
the side of the skull and the surrounding support for the
meatus is entirely cartilaginous (
Figure 4.5
).
The middle ear of all primates is bordered laterally by
the tympanic ring which encircles the tympanic membrane
(
Coleman and Ross, 2004
). The osseous floor is formed by
the petrous portion of the temporal bone. In New World
monkeys this floor is ballooned inferiorly to form the
tympanic bulla similar to that in other mammals. Old World
monkeys and apes lack this feature.
The inner ear occupies hollowed out canals within the
petrous portion of the temporal bone immediately adjacent
to bony tubes housing the internal carotid artery and its
branches. The morphology and orientation of the semi-
circular canals in primates is similar to that of other
mammals and varies with postural and locomotor habits
(
Blanks et al., 1985; Spoor and Zonneveld, 1998; Walker
et al., 2008
).
Eye and Orbit
The eyes of primates are distinct from most other animals
in that they enable binocular vision. The orbits are rela-
tively close together with the corneas oriented anteriorly
which results in overlapping of the visual fields (
Bast,
1933; Barton, 2004
). The bony orbit of all higher primates
is complete with a well-developed postorbital bar and
