[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index][Subject Index][Author Index]

Dead Paper Walking (Repost)



Repost, because today I realized that as opposed to me myself and I,
most list members probably never got this due to formatting issues.
For your convenience, typos have been removed:


Due to a few recent experiences when trying to publish on the motion
range of various dinosaurs I'd like to bring this publication to the
attention of the palaeo world (mail me for PDF):

Graf, J., Stofft, E., Freese, U., and Niethard, F.U. 1993. The
ultrastructure of articular cartilage of the chicken’s knee joint.
International Orthopedics 17:113-119

Summary. The articular cartilage and synovial membrane of immature and
mature chicken knee joints were studied by light, scanning and
transmission microscopy. The findings differed from human articular
cartilage and we conclude that the chicken knee joint is not suitable
as a model for human joint degeneration.


Sounds like boring medical stuff, doesn't it?
Some excerpts from the results and discussion:

"A characteristic feature was the presence of blood vessels within the
cartilage"
"Many collagen fibres were seen under the light microscope (Fig. 1).
[...](I)n mature birds [...] the fibres [...] were orientated in
parallel near the surface but in the deeper zones they ran either in a
vertical direction or were arranged in a network extending into the
calcified zone next to the underlying bone."
"Light microscopy demonstrates that in addition to the presence of
blood vessels the most conspicuous difference was the regular
occurrence of unmasked collagen fibres in chicken cartilage."
"There were also definite differences in the arrangement of the
collagen fibres. In the hyaline cartilage of humans and other mammals,
superficial fibres run parallel to the articular surface; a second
deeper layer runs parallel to the surface for a short distance only,
and then bends towards the deeper zones to form arcades which
superficially merge with adjacent arcades, so that the fibres cross
each other forming acute angles [...]. In chickens, only some fibres
are arranged in this way, and most form bundles which run in different
directions."

Remember that old argument:
'Dinosaur articular cartilage could not have been a thick cap, because
it would not have been sufficiently supplied with nutrients'?
It is just plain wrong: dinosaurs very likely had blood vessels
supplying thick caps of cartilage, of which only the outermost part
was similar to the hyaline cartilage in mammalian joints. The next
time you have chicken, try pulling the knee apart and check the shape
and thickness of the cartilage cap. You may be surprised........

:)
Heinrich