Changes Occurs in the Shape of Cells during Morphogenesis | Embryology

In this article we will discuss about the mechanism of changes occurs in the shape of cells during morphogenesis.

Electron microscopic studies of cells undergoing changes in shape have shown that a peculiar group of cytoplasmic structures are involved in these processes. They are the microtubules and microfilaments. The microtubules are seen as long, straight, un-branched rods, 200 to 250 Å in diameter, which appear hollow in cross sections.

In cells not undergoing changes in shape the microtubules may be observed to traverse the cytoplasm at random. In cells which are elongating in a certain direction, however, the microtubules are arranged in parallel bundles running in the direction in which the cell is elongating.

Bundles of such microtubules are prominent in the narrowed “necks” of the bottle-shaped cells of the amphibian blastopore, in the cells immigrating from the primitive streak in birds, and in the cells of the neural plate. Bunches of microtubules may be seen along the length of outgrowing processes of nerve cells, and they are also involved in mitosis, as the fibers of the achromatic spindle.

It was originally with the spindle fibers of mitosis that the microtubules were found to be very sensitive to certain poisons, namely, colchicine (an alkaloid extracted from plants of the lily family) and also vinblastine sulfate. In cells treated with these poisons the microt