title: An ultrastructural study of the perichondrium in cartilages of the chick embryo.
abstract: The ultrastructure of perichondrial tissue of cartilage rudiments (metatarsus, tibiotarsus and sternum) of the chick embryo at various stages of development (H.H. stages 28-45) was investigated by transmission electron microscopy. Previous microscopic and submicroscopic data were generally confirmed, but new findings indicated: (a) the existence of a temporary syncytial state of perichondroblasts during the earliest developmental stages, (b) the existence of a perichondrial cambial layer of stem cells, (c) involvement of perichondroblasts in the appositional growth of cartilage. Electron microscopy revealed clear temporal relations between cell differentiation, perichondrial growth and the structure and production of perichondrial ECM. In addition, the boundaries between cartilage and perichondrial tissue were demonstrated unambiguously. Perichondrial structure varied specifically with each cartilage segment; in particular the perichondrium in long bone rudiments (where ossification starts early) contrasted with that in the permanent cartilage medial process of the sternum.
authors.affiliation: Dipartimento di Fisiologia e Biochimica Generali, Sezione di Istologia ed Anatomia Umana, Milano, Italy.
authors.forename: A
authors.initials: A
authors.lastname: Bairati
authors.forename: M
authors.initials: M
authors.lastname: Comazzi
authors.forename: M
authors.initials: M
authors.lastname: Gioria
mesh_terms: D000367:Age Factors; D000818:Animals; D002356:Cartilage / Q000196:embryology* / Q000648:ultrastructure*; D002642:Chick Embryo; D018483:Diaphyses / Q000196:embryology / Q000648:ultrastructure; D005109:Extracellular Matrix / Q000648:ultrastructure; D006614:Hindlimb / Q000196:embryology / Q000648:ultrastructure*; D007365:Intercellular Junctions / Q000648:ultrastructure; D008648:Mesoderm / Q000648:ultrastructure; D008854:Microscopy, Electron; D013249:Sternum / Q000196:embryology / Q000648:ultrastructure*