Various highly complex and sophisticated mechanisms of apoptosis have been identified, but two main pathways include 1) extrinsic (death receptor pathway) and 2) intrinsic (mitochondrial pathway). The extrinsic pathway is initiated when a ligand binds to a receptor in the membrane and sends signals downstream to initiate apoptosis. The intrinsic pathway is initiated when changes are detected within the mitochondria and it signals a cascade effect of caspase activation. While the two apoptotic pathways seem distinct, recent evidence suggest that the two pathways may be linked and can influence one another.