- If the substance is put directly into the bloodstream, the gland is called endocrine gland.
- If the substance is carried by a duct, the gland is called an exocrine gland. Exocrine ducts empty outside the body, or into cavities inside the body.
Examples of glands in humans are:
- Sweat glands that produce sweat for perspiration.
- The pineal gland in the brain, which produces the hormone melatonin at night.