Compare endocrine and exocrine glands in terms of ducts and product release.

• A. Exocrine glands secrete through ducts onto surfaces; endocrine glands are ductless and release hormones into the bloodstream.
• B. Exocrine glands are ductless and release hormones into the bloodstream; endocrine glands have ducts.
• C. Exocrine glands secrete hormones into bloodstream; endocrine glands secrete enzymes onto surfaces.
• D. Endocrine glands secrete through ducts onto surfaces; exocrine glands release hormones into bloodstream.

Answer: (A)

The key idea is how secretions exit the gland and where they go. Exocrine glands use ducts to carry their products to an external surface or a body cavity—think saliva into the mouth or sweat onto the skin. Endocrine glands lack ducts and release their products, hormones, directly into the bloodstream so they can travel to distant targets. This distinction also explains why some organs have both types of tissue, like the pancreas, where the exocrine portion dumps digestive enzymes into the small intestine via a duct, while the endocrine portion releases hormones like insulin into the blood.