The secretion is an action leading a cell to send in the extracellular Milieu a substance (Hormone, Neurotransmetteur, Glycoprotéine S). The process of Sécrétion implies the fusion of Vésicule S (containing the substance to be secreted) with the cytoplasmic membrane (or plasmic Membrane) of the cell, thus releasing the contents of the blister outside the cell.

The constitutive secretion is the secretion which relates to all the cells whereas the secretion controlled is a specific secretion of certain differentiated cells.

Simple: Secretion