A lysosome is a membranous bag containing hydrolytic enzymes that the cell uses to digest macromolecules. Lysosomes bud off from the Golgi apparatus. Some of the granules of the granulocytic white blood cells are lysosomes.
Phagocytic vacuoles fuse with the lysosome, whose enzymes digest the phagocytosed matter. The lysosomes also engulf worn-out components of the cell in which they are located, forming autophagic vacuoles, and returns the digested products for reuse by the cell. When a cell dies, lysosomal enzymes cause autolysis of the remnants. Programmed cell destruction by lysosomal enzymes is often important in the process of development.
For example, in the embryonic stage, the hands are webbed till lysosomes digest the tissues between the fingers. Small amounts of enzymes that leak out of lysosomes into the cytosol normally get inactivated due to the absence of acidic pH. However, large leakages cause tissue destruction. In gout, phagocytes ingest uric acid crystals and such ingestion triggers the extracellular release of lysosomal enzymes, which contribute to the inflammatory response in the joints.