Vesicular transport is a cellular process that encompasses the engulfment of particles or dissolved substances by cells. It involves endocytosis, transcytosis, and exocytosis.

Endocytosis is a cellular mechanism that involves the inward folding of the cell membrane to create vesicles that capture and transport large drug molecules. This process comprises two distinct methods: pinocytosis (often referred to as "cell drinking") and phagocytosis (often referred to as "cell eating"). Pinocytosis is a special form of endocytosis that enables the cell to absorb small fluid droplets. This process occurs when tiny structures known as caveolae on the cell surface detach and transform into fluid-filled vesicles that move freely within the cytoplasm. On the other hand, phagocytosis is a unique endocytic mechanism that enables cells to ingest large macromolecules, bacteria, or cellular debris, forming phagosomes.

Transcytosis is another key endocytic mechanism that involves the transportation of endocytic vesicles laden with drugs across a cell, eventually merging with the cell's outer membrane. This method is crucial for absorbing large protein molecules and certain vaccines like the Sabin polio vaccine.

Conversely, exocytosis represents the reverse process of endocytosis. During exocytosis, intracellular vesicles fuse with the cell membrane to expel their contents. For example, insulin-producing cells in the pancreas employ exocytosis to package and discharge insulin into the bloodstream.