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The Ultrastructure of the Plumula of the Tooth of Lytechinus variegatus (Echinodermata: Echinoidea)
Author(s) -
Chen ChangPo,
Lawrence John M.
Publication year - 1986
Publication title -
acta zoologica
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.414
H-Index - 37
eISSN - 1463-6395
pISSN - 0001-7272
DOI - 10.1111/j.1463-6395.1986.tb00847.x
Subject(s) - odontoblast , endoplasmic reticulum , ultrastructure , biology , golgi apparatus , microbiology and biotechnology , cytoplasm , vacuole , anatomy , materials science , dentin , composite material
The plumula is enclosed by a single layer of epithelial cells. There are two types of odontoblasts: syncytial and free odontoblasts. Syncytial odontoblasts are arranged linearly on the abaxial side and have a highly active Golgi complex, rough endoplasmic reticulum, large and round mitochondria, and small coated vesicles indicative of a high level of secretory activity. Free odontoblasts cluster on the adaxial side and have patchy chromatin and little cytoplasm. The free odontoblasts migrate to the abaxial side, where their structure changes to that of syncytial odontoblasts. Calcareous deposits are formed intracellularly by syncytial odontoblasts within two membranes: an outer plasma membrane and an inner vacuolar membrane. The vacuolar membrane has organic particles on the surface of the membrane. There is no trace of organic matter within the calcareous deposit. Fibroblasts are located on the adaxial side. Collagen fibers are located primarily on the adaxial side adjacent to the calcareous depositing membranes and between free odontoblasts, but they are not located in the deposits. Collagen fibers may play a role in cell migration and thus in calcification. The morphological changes of the plumulae are closely related to calcification.