Annulate lamellae

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                                                          ANNULATE LAMELLAE
Annulate lamellae were discovered by McCulloch in 1952. He observed in many germ cells and also in somatic cells of invertebrates and vertebrates.These are usually observed in cytoplasm and also seen in nucleus.These are found in foetal cells where high metabolic activity takes place.It consist of double membraned sheets.They are structurally similar to nuclear envelope by having pores with annular masses. Annulate lamellae is also formed from nuclear envelope . The outer membrane of nuclear envelope forms finger like projections which are pinched off into the cytoplasm in forms of blebs. Since there is formation of blebs this process is called blebbing. Rows of such vesicles migrate towards the periphery of the cell and fuses to form cisternae. Matrix material becomes associated with the pores of each cisternae to form annuli, resulting in the formation of an annulate lamellae. Annulate lamellae represent intermediate stage in the formation of the endoplasmic reticulum. This occurs by losing of pores annulate lamellae by deposition of ribosomes on their surfaces.