Acellular matrix products differ mainly in the source of cells and tissue materials and methods used during manufacture. A variety of animal- and human-derived products are available: Products derived from animal sources (xenografts) are developed by harvesting living tissue (eg dermis, small intestine submucosa, pericardium, etc) from various donor animals (eg porcine, equine or bovine) at different stages of development. The tissue materials are subsequently processed to remove the cells (decellularisation), leaving the collagen matrix. Products derived from animal sources may consist of the tissue scaffold only (eg Unite® BioMatrix Collagen Wound Dressing, Synovis) or may be combined with synthetic materials to create a composite product (eg INTEGRA® Bilayer Matrix Wound Dressing, Integra LifeSciences). Products derived from human sources, ie donated human cadaver skin (allografts), undergo various processes to remove the cells and deactivate or destroy pathogens (eg AlloDerm®, Lifecell; GraftJacket®, Wright Medical).