noun, plural: endocrine glands
Any of the ductless glands secreting hormones that are released directly into the circulation and influence metabolism and other bodily functions
The endocrine system is one of the biological systems of humans and other vertebrates. It is comprised of the endocrine glands.
The endocrine glands are ductless glands that release secretions (hormones). They do not require ducts to reach and influence target cells. The endocrine glands release hormones into the blood or lymph to reach and act on specific cells of organs. These glands aid in controlling the bodily metabolic activity, as well as serve as chemical messengers that allow cells to communicate with one another. Nevertheless, the endocrine glands are not the only tissues that secrete hormones. Autocrines (tissues that secrete chemical messengers that act on the cell that secretes them) and paracrines (tissues that secrete chemical messengers that act on nearby cells) are not considered endocrine glands. Hormones released by endocrine glands into the circulation and act on distant cells employ a form of chemical signaling referred to as endocrine signaling.
The major human endocrine glands include:
• pituitary gland
• thyroid gland
• adrenal glands
• pineal gland
• parathyroid gland
The endocrine glands may be contrasted to the exocrine glands that also secrete hormones. However, the exocrine glands (e.g. salivary gland, sweat, gland, etc.) make use of ducts. The liver and the pancreas are considered both an endocrine gland and an exocrine gland. Some of the substances are released through ducts and others are released into the bloodstream.