In glandular epithelial tissue, which statement best describes the difference between exocrine and endocrine glands?

• A. Exocrine glands are always unicellular, whereas endocrine glands are always multicellular.
• B. Exocrine glands release hormones directly into the bloodstream, whereas endocrine glands secrete their products through ducts onto body surfaces.
• C. Exocrine gland secretions are always lipid-based, whereas endocrine gland secretions are always protein-based.
• D. Exocrine glands secrete their products through ducts onto an epithelial surface, whereas endocrine glands release hormones into the interstitial fluid and then the bloodstream.

Answer: (D)

Verified step by step guidance

1. Step 1: Understand the basic definitions of exocrine and endocrine glands. Exocrine glands secrete their products onto epithelial surfaces, usually through ducts, while endocrine glands release hormones directly into the interstitial fluid and then into the bloodstream.
2. Step 2: Recognize that exocrine glands can be unicellular or multicellular, so the statement about exocrine glands always being unicellular is incorrect.
3. Step 3: Note that endocrine glands do not secrete their products through ducts; instead, they release hormones into the bloodstream, which contradicts the statement that endocrine glands secrete through ducts onto body surfaces.
4. Step 4: Understand that the chemical nature of secretions (lipid-based or protein-based) is not a defining difference between exocrine and endocrine glands, as both types can secrete various substances.
5. Step 5: Conclude that the key difference lies in the mode of secretion: exocrine glands use ducts to deliver their products to epithelial surfaces, whereas endocrine glands release hormones into the interstitial fluid and bloodstream.