Glands. Glands of the body are classified as either exocrine or endocrine types. Exocrine glands are glands that retain ducts to body surfaces. During development, endocrine glands lose their contacts to embryological surfaces(ducts) and become isolated as small blocks of tissues.odes of Secretion. Secretory cells of exocrine glands release their products into ducts in three different ways. The mode of secretion can be classified as merocrine, apocrine, or holocrine. Cells that secrete products via the merocrine method form membrane-bound secretory vesicles internal to the cell.