There are three pathways involved in the exocytotic process.

This type of exocytosis involves the delivery of membrane proteins and lipids to the cell membrane and to also get rid of substances from the cell into the exterior. This is the most common pathway that is performed by all body cells.

Generally, this mechanism depends on extracellular signaling for the release of its content onto the outer part of the cell.

The secretion of these products must be triggered by extracellular signals to initiate the formation of secretory vesicles, which fuse with the cell membrane for a long time to allow the release of the cell contents out of the cell, into the exterior. After delivery, the vesicles are reformed and returned to the cytoplasm.

This mechanism is common among the secretory cells whose function is to store hormones, digestive enzymes, and neurotransmitters.

This process involves the fusion of cell vesicles with the cell lysosomes. Lysosomes contain digestive enzymes and hydrolase enzymes whose function involves the breakdown of cellular waste materials, microorganisms, and debris. The lysosome carries the elements that have been broken down onto the cell membrane where it fuses with the cell membrane releasing its elements into the extracellular cell matrix.

Of the three discussed pathways, constructive exocytosis is the regular exocytotic mechanism that takes place in four steps while the regulatory exocytosis takes place in five steps. The steps include:

Vesicle trafficking – The cell vesicles are transported to the cell membrane through the microtubules of the cytoskeleton with the help of the motor proteins such as kinesins, dyneins, and myosins.

Tethering – When the cell vesicles reach the cell membrane that is pulled toward the cell membrane and they eventually come into contact with each other.

Docking – This is the attachment of the vesicles with the cell membrane, initiating the merging of the phospholipids of the vesicle membrane with that of the cell membrane.

Priming – This step takes place in the regulated exocytosis and not in the constitutive exocytosis. There are modifications that take place in some of the cell membrane elements for exocytosis to take place, which assist in signaling processes that trigger exocytosis.