Gland

A group of specialized cells that manufacture and release chemical substances, such as hormones and enzymes, into the body. There are two main types of glands: endocrine and exocrine. Endocrine glands do not have ducts and release their secretions directly into the bloodstream; examples include the pituitary, thyroid, and adrenal glands. Exocrine glands have ducts and release their secretions either on to the surface of the skin (sebaceous glands) or into a hollow structure such as the mouth or digestive tract (salivary glands). Lymph nodes are sometimes referred to as glands, particularly when they are enlarged (see glands, swollen). Strictly speaking, this is incorrect usage because lymph nodes do not secrete chemical substances.