How do exocrine glands differ from endocrine glands?

• A. Exocrine glands secrete only sebum, whereas endocrine glands secrete only sweat.
• B. Exocrine glands secrete their products through ducts onto an epithelial surface or into a lumen, whereas endocrine glands secrete hormones into the interstitial fluid and then the bloodstream.
• C. Exocrine glands release hormones directly into the bloodstream, whereas endocrine glands secrete through ducts onto body surfaces.
• D. Exocrine glands are always unicellular and produce only mucus, whereas endocrine glands are always multicellular and produce only enzymes.

Answer: (B)

Verified step by step guidance

1. Step 1: Understand the basic definitions of exocrine and endocrine glands. Exocrine glands release their secretions onto epithelial surfaces or into body cavities through ducts, while endocrine glands release hormones directly into the bloodstream without using ducts.
2. Step 2: Identify the type of substances secreted by each gland. Exocrine glands secrete substances such as enzymes, mucus, or sebum, which act locally, whereas endocrine glands secrete hormones that travel through the blood to target distant organs.
3. Step 3: Recognize the structural differences. Exocrine glands typically have ducts that carry their secretions to specific sites, while endocrine glands are ductless and release hormones into the interstitial fluid surrounding the cells.
4. Step 4: Analyze the options given in the problem to determine which correctly describes these differences. Focus on the presence or absence of ducts and the destination of the secretions (epithelial surface vs. bloodstream).
5. Step 5: Conclude that the correct distinction is that exocrine glands secrete their products through ducts onto epithelial surfaces or into lumens, whereas endocrine glands secrete hormones into the interstitial fluid and then the bloodstream.