D
davidford
Guest
Part 1 of 2
“the panda’s thumb… it is not a good design”
How so?
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Endo et al. 1999. "Role of the giant panda’s ‘pseudo-thumb’
Nature 397: 309-310.
Hideki Endo*, Daishiro Yamagiwat+, Yoshihiro Hayashit+,
Hiroshi Koiet++, Yoshiki Yamaya++, Junpei Kimura++
*Department of Zoology, National Science Museum, Tokyo,
Shinjuku, Tokyo 169, Japan e-mail: [snip]
+Department of Veterinary Anatomy, University of Tokyo,
Tokyo 113, Japan
++College of Bioresource Sciences, Nihon University,
Kanagawa 252, Japan
The article’s entire text:
The way in which the giant panda, Ailuropoda
melanoleuca, uses the radial sesamoid bone-- its
‘pseudo-thumb’-- for grasping makes it one of the most
extraordinary manipulation systems in mammalian
evolution^1-5. The bone has been reported to function as
an active manipulator, enabling the panda to grasp bamboo
stems between the bone and the opposing palm^2, 6-8. We
have used computed tomography, magnetic resonance
imaging (MRI) and related techniques to analyse a panda
hand. The three-dimensional images we obtained indicate
that the radial sesamoid bone cannot move independently
of its articulated bones, as has been suggested^1-3, but
rather acts as part of a functional unit of manipulation. The
radial sesamoid bone and the accessory carpal bone form a
double pincer-like apparatus in the medial and lateral sides
of the hand, respectively, enabling the panda to manipulate
objects with great dexterity.
“the panda’s thumb… it is not a good design”
How so?
////////////////////////////////////////////////////////////////////////////////////
Endo et al. 1999. "Role of the giant panda’s ‘pseudo-thumb’
Nature 397: 309-310.
Hideki Endo*, Daishiro Yamagiwat+, Yoshihiro Hayashit+,
Hiroshi Koiet++, Yoshiki Yamaya++, Junpei Kimura++
*Department of Zoology, National Science Museum, Tokyo,
Shinjuku, Tokyo 169, Japan e-mail: [snip]
+Department of Veterinary Anatomy, University of Tokyo,
Tokyo 113, Japan
++College of Bioresource Sciences, Nihon University,
Kanagawa 252, Japan
The article’s entire text:
The way in which the giant panda, Ailuropoda
melanoleuca, uses the radial sesamoid bone-- its
‘pseudo-thumb’-- for grasping makes it one of the most
extraordinary manipulation systems in mammalian
evolution^1-5. The bone has been reported to function as
an active manipulator, enabling the panda to grasp bamboo
stems between the bone and the opposing palm^2, 6-8. We
have used computed tomography, magnetic resonance
imaging (MRI) and related techniques to analyse a panda
hand. The three-dimensional images we obtained indicate
that the radial sesamoid bone cannot move independently
of its articulated bones, as has been suggested^1-3, but
rather acts as part of a functional unit of manipulation. The
radial sesamoid bone and the accessory carpal bone form a
double pincer-like apparatus in the medial and lateral sides
of the hand, respectively, enabling the panda to manipulate
objects with great dexterity.
Code:
{Figure 1 Schematic drawings of the grasping mechanism
of the giant panda (medial view of right hand, with the
proximal direction at the bottom).
a, Hand open.
b, Hand open but with the phalanges flexed.
c, The grasping action (from a small palmar angle). The
radial sesamoid and accessory carpal bones do not move
independently of their articulated bones in the grasping
action, but constitute two functional units: the PRO
complex (see text) in the medial part of the hand, and the
AU complex (see text) in the lateral part. Pincer-like
structures are made by the phalanges and the RRM
complex in the medial part, and by the phalanges and the
AU complex in the lateral part
d, As c, but showing the muscles in the pincer-like
structures on both sides of the grasped hand (arrows).}
Schematic drawings based on computed tomography and
three-dimensional reconstructed images (Fig. 1a-c) explain
the grasping mechanism used by the giant panda.
Three-dimensional data obtained from artificial grasping of
a carcass hand show that the radial sesamoid bone does not
abduct or adduct independently of the first metacarpal and
the radial carpal bones, and that the accessory carpal bone
does not move substantially in the gripping action. When
the movement is compared for open and gripping hands,
the radial sesamoid bone, the first metacarpal and the radial
carpal are actually moulded into a single bone, and the
accessory carpal bone and the ulna constitute a single
functional unit. When the hand is opened, the radial
sesamoid bone and the accessory carpal bone therefore
protrude at different angles from the plane of the palm (Fig.
1a).
The radial carpal bone forms an enlarged articulated
surface to the distal end of the radius. In the gripping
action, the five long phalanges are crooked (Fig. 1b) while
the panda flexes the wrist joint (Fig. 1c). This wrist flexion
means that the radial sesamoid bone is parallel to the
accessory carpal bone, and the distal phalanges are parallel
with the radius and ulna. This arrangement gives the panda
a degree of opposability between the phalanges and the
functional unit comprising the radial sesamoid bone and
the accessory carpal bone (Fig. 1c).
The radial sesamoid bone and the accessory carpal bone do
not move independently of their articulated bones in the
grasping action, but constitute a functional unit with the
first metacarpal and the radial carpal, and the ulna,
respectively. The panda has three functional units: the
RRM complex (radial sesamoid -- radial carpal -- first
metacarpal), the AU complex (accessory carpal -- ulna),
and the phalanges (Fig. 1a-c). The RRM complex flexes
and the radial sesamoid bone becomes parallel with the
accessory carpal bone, and the phalanges bend and hold
They weren’t available when I started on Fidonet. What’s with all the links to Google Groups? 
:whacky:
