koski1968 BAUME

Volume 54
Number 8
Cranial growth centers 575
Fig. 10. The condyle of a Sday-old rat. There is a relatively wide intermediate layer (the
upper third of the nonossified top of the condyle, excluding the narrow darkly stained articular
zone), a narrow zone of cartilage cells, and a wide zone of hypertrophic cells (darkly
stained). Note the absence of a structural organization, as seen in the epiphyseal growth
plate in Fig. 1. (Courtesy of Dr. 0. Ronning.)
dible. It is not an articular cartilage, nor is it an epiphyseal growth plate
(Fig. 10). It does not even form from the same embryonic precursor tissue as
the epiphyseal cartilages,53 36 a fact which may have something to do with its
structure and function.
It is claimed that the condylar cartilage grows not interstitially, like the
epiphyseal cartilages, but appositionally from the deepest layer of the connective
tissue cover of the condyle.82~ 83185l 86p 9o Th’ is mitotic layer responsible for the
increase of the cartilage is also called the intermediate layer. It is located between
the surface of the condyle and the cartilaginous portion of it,12 and the
cells of this layer are not cartilage cells but are rather like undifferentiated
mesenchymal cells.7o In the epiphyseal cartilages, as we know, the proliferating
cells are cartilage cells. There are other differences between the condylar cartilage
and the epiphyseal growth cartilages. The structural organization present
in the epiphyseal growth apparatuses is lacking in the condylar cartilage, and
the zone of nonhypertrophic cartilage cells in the condyle is very narrow, the
forming cartilage cells turning hypertrophic almost immediately,12> 7o as in the
clavic1e.l It is of special interest that the whole hypertrophic area in the condylar
cartilage seems to be in a state of mineralization, whereas in the epiphy-