Exocrine Glands: These are glands that secrete substances through ducts directly to the target area, such as sweat glands or salivary glands.
Endocrine Glands: Endocrine glands secrete hormones directly into the bloodstream, allowing them to reach various target organs throughout the body.
Neurotransmitters: While not produced by glands, neurotransmitters can be seen as similar to secreted hormones since they are chemical messengers that transmit signals between nerve cells in the brain and body.