Exocytosis CGI image.  Exocytosis is the process by which a cell actively transports and fuses secretory vesicles with the plasma membrane and the extracellular space.  There are three pathways of exocytosis, each delivering vesicles to the plasma membrane. The constitutive secretory pathway, found in all cells, operates continuously to release freshly synthesized membrane lipids and proteins.  As well as soluble secretory proteins from the Golgi network directly to the plasma membrane. The regulated secretory pathway operates in specialized cells that secrete specific cargo, such as hormones, neurotransmitters, or enzymes.  In these cells, secretory vesicles accumulate and concentrate their cargo through retrograde movement through the Golgi. Once the vesicles are loaded to the correct concentration, they are transported via cytoskeleton tracks near the site of secretion, such as the synapse in neurons, until a signal prompts them to fuse and release their contents. The third sorting pathway, lysosomal exocytosis, involves the fusion of lysosomes with the plasma membrane. This pathway can deliver extra membrane for repair, eject undigested debris from the cell, and secrete cargo such as pigment.