OSMOSIS
AND ENDOCHONDRAL OSSIFICATION
Olusola O.A. Oni
The Glenfield Hospital, Groby Road, Leicester LE3 9QP, UK
Endochondral ossification
whereby cartilage
is transformed into bone is the key event in bone development, growth
and repair. During this process, the cartilage cells enlarge. Osmosis
may be a potential cause for this. Chick embryo ulnae were fixed in
Karnovsky fixative, serially dehydrated and then embedded in Araldite
resin. Hindlimb bones from 5-day old NZW rabbits were fixed in buffered
formalin, decalcified in Kristensen's solution and processed into paraffin
wax. Sections stained respectively using haematoxylin-eosin and Toluidine
blue were then examined microscopically. Cell hypertrophy occurred only
in areas where the cartilage anlage adjoined blood vessels. Elsewhere
the cells are flattened. Cell rupture and bone formation occurred only
in areas where vessels had eroded into the cartilage. The key features
of two adjoining aqueous milieu (blood and cartilage) separated by a
thin partition and, cell enlargement and cell rupture provide an indirect
evidence that an osmotic process is at play.