Innerbody.com explains that all of the body’s glands are part of the endocrine system, but the glands themselves are scattered throughout the body. Certain glands, including the parathyroid, thyroid, pituitary and pineal glands, are concentrated in the head or neck. By contrast, the thymus gland is located in the upper torso, whereas the adrenal glands, ovaries, pancreas and testes are located in the lower abdomen.
While Innerbody.com describes all of the body’s glands as part of the endocrine system, other resources include exocrine glands among the body's true glands. Exocrine glands differ from endocrine glands in that they have a duct through which their secretions exit rather than secreting the product directly into the bloodstream as endocrine glands do. Wikipedia lists sweat glands and saliva glands as examples of exocrine glands. Saliva glands are located in the mouth, whereas sweat glands are found throughout most of the body.
Innerbody.com indicates that the nervous system controls all of the endocrine glands. The glands in turn produce and secrete hormones, which help to maintain constant conditions inside the body. For example, the pancreas produces enzymes that digest food and hormones, such as insulin and glucagon, that keep the body’s blood sugar concentration stable.