What are the cis, medial, and trans compartments of the Golgi apparatus?

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Diagram of the Golgi apparatus showing its stacked, curved membranes with labeled parts including cisternae, cis face, trans face, lumen, and various vesicles involved in cellular transport and secretion. — Golgi apparatus A membrane-bound organelle of eukaryotic cells, the Golgi apparatus is made up of a series of flattened, stacked pouches called cisternae that function as a series of compartments that progressively refine and direct cellular products to their proper destinations. .

The Golgi apparatus is a polarized organelle consisting of three primary, biochemically distinct compartments that facilitate the modification and sorting of proteins and lipids. These compartments are organized as follows:1

Cis compartment: Located nearest to the endoplasmic reticulum, this region receives proteins and lipids via fused vesicles. It contains the cis Golgi network, which is responsible for the initial sorting of incoming molecules.1
Medial compartment: These represent the central layers of cisternae within the stack, where specific enzymatic modifications—such as the removal of mannose moieties—continue to occur as molecules progress through the organelle.1
Trans compartment: Situated farthest from the endoplasmic reticulum, this region includes the trans Golgi network. It is the final processing site where additions like galactose or sulfate occur, and where molecules are sorted and packaged into vesicles for delivery to their final destinations.1