A gland is an organ in an animal's body that synthesizes a substance for release such as hormones, often into the bloodstream (endocrine gland) or into cavities inside the body or its outer surface (exocrine gland).
Humans have a large variety of glands, from the pituitary gland in the brain, to sweat glands over the body's skin that release perspiration to regulate the body's temperature. Other well known glands include the adrenal glands, the prostate gland, the thyroid gland, the pineal gland, the thymus and mammary gland. Two other paired glands are the parotid glands and submandibular glands, both involved in saliva production.