1. A layer of hydrophilic polysaccharide that covers the surface of some Gram-positive and Gram-negative bacteria, giving colonies a ‘smooth’ appearance. The hydrophilicity inhibits phagocytosis by leucocytes and thus contributes to pathogenicity.
2. A multicellular layer of cells surrounding a foreign object too large to be phagocytosed. In some cases the cells may fuse to form multinucleate giant cells.
3. A dense connective tissue sheath around an organ.