koski1968 BAUME

5 68 Koski
Fig. 2. A schematic illustration of the two &Bering views on the structure of the suture. A
represents the three-layer concept; B, the five-layer concept (see text).
B
One school of thoughP+ go sees the suture as a. three-layer structure. It maintains
that the connective tissue between the two bones plays the same part as
the cartilage at the base of the skull, in the epiphyses, and on t,he articular
surfaees of long bones, that is, there is n “spreading” of the suture, initiated by
the proliferation of the middle layer cdls of the sutural tissue. This concept
appears to imply the existence of “tissue-separating force” in the sutural tissue.
The other concept regards the suture as a five-la.yer structure.62, *O, 81 Each
bone at the suture has its own two-layer periosteum covering also the opposing
surfaces of the bones as if the bones were in a package, and there is a fifth layer
between these periosteal layers. The role of this fifth layer is seen in allowing
for slight adjustments between the bones during growth, while the active proliferating
role is played by the cambial layers of the periosteums of each
bone 26, 51, 62, 75
When histologic specimens of sutures are examined, it is obvious that men
of both schools of thought must have studied the same structures, and they
differ only in the interpretation of the structures (Fig. 3).
It may be mentioned in passing that cartilage tissue has been observed in
the suture areas,54l 62 but it has not been found to be of significance as a growth
center; in some instances, it appears at t.he time of the closure of the suture.54
It is quite clear that the structure of a suture is not at all similar to that of
an epiphyseal growth plate. The question remains: is there an expansive force?
Is the growth in the sutural area of primary nature, that is, does it have an
independent growth-promoting potential, thereby pushing the bones apart, or
is it of secondary nature, a response to some factor or factors, primarily effecting
the separation of the bones and thus necessitating or allowing for an apposition
at the bone surfaces ? (Fig. 4.)
Some authors maintain that “there is no doubt that sutural growth is a
primary and active mechanism for the enlargement of the cranium” and that