Which statement about exocrine glands is true?

• A. They secrete hormones into lymph.
• B. They lack ducts and release secretions into blood.
• C. They are only tied to sweat glands.
• D. They contain ducts and empty their products onto a surface.

Answer: (D)

Exocrine glands deliver their secretions through ducts to a surface. This is what sets them apart: their products exit onto the skin or mucosal surfaces, such as sweat glands releasing sweat onto the skin or salivary glands delivering saliva into the mouth. In contrast, endocrine glands release hormones directly into the bloodstream for distribution, not onto surfaces. The statement describing exocrine glands as lacking ducts or releasing secretions into blood, or being limited only to sweat glands, doesn’t fit the defining feature. The true idea is that exocrine glands have ducts and empty their products onto a surface.