Étude ultrastructurale de l'os des vertèbres du Sélacien Scyliorhinus canicula L.

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Abstract
The neural arches of the vertebrae of Scyliorhinus canicula were studied in detail. The extremities of each half arch consist of two pyramids of fibrous cartilage. These contain rows of convergent collagen fibers in the shape of a fan. The cells are arranged in series without forming real columns and without becoming enlarged. The central area of each arch contains a band of calcified cartilage with degenerating cells and numerous gaps that are invaded by urchin-shaped calcifications. This blade of cartilage is squeezed between an internal band of lamellar bone and an external nonlamellar zone of bone. The internal bony zone is bordered by osteoblasts and contains elongated osteocytes, many showing signs of degeneration. The external zone contains osteocytes joined by small canaliculi. Areas of resorption by mononucleated cells can be observed at the border of the external bone zone. These cells project digitations that the calcified border where fragmented collagen fibers are present; they react positively to acid phosphatases and show numerous signs of pynocytosis.[Journal translation]