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Figure 10 | Frontiers in Zoology

Figure 10

From: Development and epithelial organisation of muscle cells in the sea anemone Nematostella vectensis

Figure 10

Schematic representation of organization and development of muscle cells. A Modes of muscle cell organization. The type 1 muscle cell corresponds to the classical epitheliomuscular cell. The cell is integrated into the epithelium by apical cell-cell junctions, connecting them to neighboring cells, while the basal part is elongated and houses myofilaments. Type 2 muscle cells are still epitheliomuscular; their connections between the apical and the basal part, however, are drawn out to form thin and elongated cytoplasmatic bridges. In type 3 muscle cells the apical cell junctions have been lost, resulting in a sinking to the base of the epithelium, with the nucleus situated near the myofilaments. B + C Development of type 2 & 3 muscle cells. In both types myofilaments start to become accumulated at the base of epithelial cells. B In type 2 muscle cells the apical cell-cell junctions remain and the connection between the apex and the base becomes constricted to form thin and elongated cytoplasmic bridges. The basally situated myonemes build up a continuous and folded muscle sheet. C Type 3 muscle cells lose their apical cell-cell junctions and sink down to the base of the epithelium, where they are arranged in a discontinuous muscle layer, enabling overlying epithelial cells to attach to the mesoglea. Color code: yellow: mesoglea, blue: epithelium, red: myofilaments, grey, nucleus.

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