Secretory vesicles are small, membrane-bound sacs within cells that transport proteins and other molecules to the cell membrane. They are formed by the Golgi apparatus, which processes and packages proteins synthesized in the endoplasmic reticulum. Once filled, these vesicles move to the cell surface to release their contents outside the cell. When a secretory vesicle reaches the cell membrane, it fuses with it, allowing the contents to be released into the extracellular space. This process is essential for various cellular functions, including hormone secretion and neurotransmitter release, playing a crucial role in communication between cells.