title: Identification and characterization of a previously undetected region between the perichondrium and periosteum of the developing avian limb.
abstract: In developing long bones, the growing cartilage and bone are surrounded by the fibrous perichondrium (PC) and periosteum (PO), respectively, which provide cells for the appositional growth (i.e., growth in diameter) of these tissues. Also during the longitudinal growth of a bone, the cartilage is continuously replaced by bony tissue, giving rise to the widely held assumption that the PC concomitantly gives rise to the PO. Except for this morphological correlate, however, no evidence exists for a direct conversion of PC cells to PO cells, and our observations presented here question this assumption. Instead, we have obtained evidence suggesting that a previously undescribed region exists between the PC and PO. This region, termed the border region (BR), has several unique characteristics which distinguish it from either the PC or PO, including (1) its lack of being determined to differentiate as either cartilage or bone, (2) its ability to preferentially elicit the invasion of blood vessels, and (3) its ability to undergo preferential growth.
authors.affiliation: Department of Anatomy and Cellular Biology, Tufts University School of Medicine, 136 Harrison Avenue, Boston, MA 02111, USA.
authors.forename: Marsha L
authors.initials: ML
authors.lastname: Crochiere
authors.forename: James K
authors.initials: JK
authors.lastname: Kubilus
authors.forename: Thomas F
authors.initials: TF
authors.lastname: Linsenmayer
mesh_terms: D000818:Animals; D002642:Chick Embryo; D019902:Chondrocytes / Q000502:physiology*; D005121:Extremities / Q000098:blood supply / Q000196:embryology*; D009924:Organ Culture Techniques; D010521:Periosteum / Q000098:blood supply / Q000196:embryology*