Which statement best distinguishes endocrine from exocrine glands?

• A. Endocrine glands release secretions onto surfaces; exocrine glands release into the bloodstream.
• B. Endocrine glands have ducts; exocrine glands lack ducts.
• C. Endocrine glands store secretions for later release; exocrine glands release immediately.
• D. Endocrine glands release secretions into the bloodstream; exocrine glands release onto surfaces or through ducts.

Answer: (D)

The main idea here is where the gland’s secretions go. Endocrine glands release hormones into the bloodstream, so the signal can travel to distant targets throughout the body (like thyroid hormones or adrenaline). Exocrine glands, on the other hand, secrete onto body surfaces or into ducts that lead to a surface or hollow organ (such as saliva through ducts or sweat onto the skin). That means the statement describing endocrine glands as releasing into the bloodstream and exocrine glands as releasing onto surfaces or through ducts best captures the distinction. The other descriptions mix up the routes or rely on storage rather than the actual path of secretion. Pancreas is a good example of both types: the endocrine part releases hormones into blood, while the exocrine part sends digestive enzymes through ducts to the intestine.