The use of human amniotic membrane based products has also been considered for the prevention of epidural fibrosis. Amniotic membrane, comprised of both amnion and chorion membranes, is metabolically active tissue which continually remodels the extra cellular matrix through processes controlled by paracrine growth factors. Amnion has 5 layers including epithelium, basement membrane, compact layer, fibroblast layer, and spongy layer. Chorion, composed of reticular layer, basement membrane, and trophoblast layer, is 3-4 times thicker than amnion. Human amniotic membrane contains growth factors which are known to stimulate epithelial cell migration and proliferation as well as many metabolic processes, including general protein and collagen synthesis, collagenase activity, and chemotaxis of fibroblasts and of smooth muscle cells. Studies have shown that amniotic membrane has inherent properties which enhance the healing process. These properties include being immune privileged, reducing inflammation, and reducing scar tissue formation. Human amniotic membrane also has antibacterial, hemostatic, and pain reduction properties, is self-signaling, and mediates tissue repair via the contained growth factors. Amniotic membrane is used in a variety of applications such as conjunctival reconstruction, pterygium repair, the treatment of burns, ulcers, chronic wounds, and wound dehiscence. An animal study has shown that amniotic membrane reduces post laminectomy epidural adhesions.