Syncytium

A syncytium (sɪn'sɪʃiəm; plural syncytia; from Greek: σύν syn "together" and κύτος kytos "box, i.e. cell") or symplasm is a multinucleate cell which can result from multiple cell fusions of uninuclear cells (i.e., cells with a single nucleus), in contrast to a coenocyte, which can result from multiple nuclear divisions without accompanying cytokinesis. The muscle cell that makes up animal skeletal muscle is a classic example of a syncytium cell. The term may also refer to cells interconnected by specialized membranes with gap junctions, as seen in the heart muscle cells and certain smooth muscle cells, which are synchronized electrically in an action potential. The field of embryogenesis uses the word syncytium to refer to the coenocytic blastoderm embryos of invertebrates, such as Drosophila melanogaster. In protists, syncytia can be found in some rhizarians (e.g., chlorarachniophytes, plasmodiophorids, haplosporidians) and acellular slime moulds, dictyostelids (amoebozoans), acrasids (Excavata) and Haplozoon. Some examples of plant syncytia, which result during plant development, include: Developing endosperm The non-articulated laticifers The plasmodial tapetum, and The "nucellar plasmodium" of the family Podostemaceae A syncytium is the normal cell structure for many fungi. Most fungi of Basidiomycota exist as a dikaryon in which thread-like cells of the mycelium are partially partitioned into segments each containing two differing nuclei, called a heterokaryon. The neurons which makes up the subepithelial nerve net in comb jellies (Ctenophora) are fused into a neural syncytium, consisting of a continuous plasma membrane instead of being connected through synapses. A classic example of a syncytium is the formation of skeletal muscle. Large skeletal muscle fibers form by the fusion of thousands of individual muscle cells. The multinucleated arrangement is important in pathologic states such as myopathy, where focal necrosis (death) of a portion of a skeletal muscle fiber does not result in necrosis of the adjacent sections of that same skeletal muscle fiber, because those adjacent sections have their own nuclear material.