Exocrine Glands: Unicellular and Multicellular Glands

Exocrine glands produce and discharge secretions onto their exterior surfaces. For example, sweat glands release sweat on the skin to maintain body temperature, while salivary glands secrete saliva inside the mouth for lubrication.

Exocrine glands are unicellular or multicellular.

Unicellular glands are individual secretory cells like the goblet cells of the intestinal epithelia.  Goblet cells secrete a complex glycoprotein called mucin onto the epithelial surface, forming a slimy protective mucus coat.

Multicellular exocrine glands consist of a group of cells which form the secretory units and produce secretions that are delivered by ducts onto the surface.

Multicellular glands are further classified based on the morphology of the ducts and the secretory units.

Based on morphology of ducts, multicellular glands are simple with unbranched ducts or compound with branched ducts.

Based on the morphology of the secretory units, they may form straight or coiled tubes and are called tubular glands, as seen in intestinal glands, or sweat glands.

In contrast, alveolar or acinar glands such as sebaceous and mammary glands, contain flask-shaped hollow secretory sacs.