Unicellular glands are considered exocrine glands because they release their product onto the surface even though they lack ducts. Which of the following is true?

• A. Exocrine
• B. Endocrine
• C. Both exocrine and endocrine
• D. Paracrine glands

Answer: (A)

The key idea is where the secretion goes. Exocrine glands release their product onto an epithelial surface or into a body cavity, even if there are no ducts. Unicellular glands do this by secreting onto the surface of the tissue—for example, goblet cells release mucus apically onto the mucous membrane. That surface-directed release defines them as exocrine. Endocrine glands, in contrast, dump their products (hormones) into the bloodstream, not onto a surface. Paracrine signaling involves secretions acting on nearby cells in the same tissue, not onto a surface. So, unicellular glands are exocrine because their secretions reach a surface, despite lacking ducts.