What is a Gland
A gland is a group of cells or organ that makes and secretes chemicals for your body to use or eliminate. Substances gland secrete included hormones, enzymes and other molecules. The function of gland secretions vary, for instance they may regulate, stimulate, protect, lubricate, catalyze or nourish.
Glands deliver their product in two ways, one is into the bloodstream and the other on an internal or external surface. Glands that secrete their substances directly into the bloodstream are called an endocrine gland and surface depositors are an exocrine gland.
Endocrine glands are ductless glands that mostly secrete hormones. These glands release their secretions into the surrounding interstitial space, which then diffuse into adjacent capillaries. Once inside, they circulate around to reach their target. As such, endocrine gland products can exert their influence body wide. Examples of endocrine glands are the thyroid, parathyroid, adrenals, pituitary and thymus.
Exocrine glands secrete their substances on a surface and their influence is generally local. The surface can be internal or external and the system of deposit is primarily through a duct. Sweat glands, sebaceous glands, salivary glands, lacrimal glands, mammary glands and gastric glands are examples of this type of gland. And the substances they excrete are sweat, sebum, saliva, tears, milk and digestive juices. Most glands in your body are the exocrine type.
Some glands have both endocrine and exocrine capabilities. Take for instance your pancreas, it secretes pancreatic juice through a duct into the small intestines to assist with digestion and it secretes insulin and glucagon into the bloodstream to help regulate blood sugar levels and carbohydrate metabolism. Another is your liver, which secretes bile into the bile ducts and secretes chemicals directly into the bloodstream that have effects on other organs. The ovaries and testes are dual performing glands as well.