Syncytium

The field of embryogenesis uses the word syncytium to refer to the coenocytic blastoderm embryos of invertebrates, such as Drosophila melanogaster.

[2] In protists, syncytia can be found in some rhizarians (e.g., chlorarachniophytes, plasmodiophorids, haplosporidians) and acellular slime moulds, dictyostelids (amoebozoans), acrasids (Excavata) and Haplozoon.

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.

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.

Cardiac action potentials propagate along the surface of the muscle fiber from the point of synaptic contact through intercalated discs.

The outer zone of the syncytium, called the "distal cytoplasm," is lined with a plasma membrane.

This plasma membrane is in turn associated with a layer of carbohydrate-containing macromolecules known as the glycocalyx, that varies in thickness from one species to another.

The proximal cytoplasm contains nuclei, endoplasmic reticulum, Golgi complex, mitochondria, ribosomes, glycogen deposits, and numerous vesicles.

[20] Syncytia can allow the virus to spread directly to other cells, shielded from neutralizing antibodies and other immune system components.

[19] "Severe cases of COVID-19 are associated with extensive lung damage and the presence of infected multinucleated syncytial pneumocytes.