The secretory pathway is a series of steps a cell uses to move proteins out of the cell, a process known as secretion. The path of a protein destined for secretion has its origins in the rough endoplasmic reticulum, a membrane-bound compartment in the cell. The protein then proceeds through the many compartments of the Golgi apparatus and finally ends up in a vesicle that transiently fuses at the cell plasma membrane via permanent plasma membrane structures called porosomes, depositing the proteins on the outside of the cell.