Can mucous and serous components mix in glands, and where does this occur?

• A. No; they are always separate glands.
• B. They mix only when secreted into ducts but not within the gland.
• C. They can mix, but only in artificial labs.
• D. Yes; they can mix in complex glands.

Answer: (D)

Secretions from mucous and serous cells can mingle when a gland contains both types of secretory units in a branching, compound structure. In complex glands like certain salivary glands, mucous tubules and serous acini coexist within the same organ. Their products are collected by a common duct system, so the mucous and serous secretions mix as they travel through the ducts. Sometimes the mucous tubules are capped by serous cells (serous demilunes), which brings the two secretions into contact within the gland. This is why the final product is a mixed seromucous secretion. So, mixing can occur in complex glands.