The Golgi Apparatus is a stack of flattened sacs called cisternae.Vesicles bud off from the rough ER are directed along the cytoskeleton to the Golgi and fuse with the cis face of the Golgi.The Golgi modifies these proteins, for example, by adding carbohydrate chains to form glycoproteins.They are then packaged into Golgi vesicles which bud off the trans face of the Golgi.These vesicles may be secretory vesicles which are transported to the cell membrane by microtubules and fuse with the cell membrane and release their contents to the exterior of the cell by exocytosis.The vesicles could also be lysosomes or contain enzymes used by the cell.