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Ductless glands are glands in human and some animal anatomy that do not have internal passageways or “ducts” for the transportation of fluids and certain cellular secretions. Most of the time, glands are designed to support larger organs, such as the liver or the brain. They can also be part of a bigger system like the endocrine system, which focuses on hormone production. No matter their specific function, one of their main roles is to shuttle signals and certain fluids from place to place. Glands without ducts usually have a slightly different operating procedure than those with them. Most rely on internal secretions, for instance, and usually also keep a much more fluid internal environment. They may also have the capacity to send their secretions to their external surface for quick absorption into the bloodstream.
Ducts are generally understood to be passageways, much like tunnels or tubes that move from place to place. The term is a familiar one in construction, where air ducts in buildings help facilitate air conditioning and heating, and their role in biology is fairly similar. They are small vessels or tubes that move materials, usually fluids and loose cellular matter, around. Sometimes these fluids go to support the functioning of other organs, but they can also shuttle things outside of the body entirely, as is the case with sweat glands and mammary glands. Ducts occur throughout the body and in many cases are the easiest way to get things moved around, but they are by no means the only way.
Most researchers view glands as organ accessories, though they are sometimes seen as small organs in their own right. Most are concerned with secretions. Glands deposit their secretions into the surroundings, into the bloodstream, or into other specific systems. Ducts are one way to effect this movement, but not all glands have them. Those without usually rely on other complementary systems.
While there are several ductless glands found in the body, the vast majority are included within the endocrine system. The endocrine system generally, and these glands as parts of it, are primarily responsible for the regulation of hormones in both male and female anatomy; the control of metabolic activity lies with them as well. The pituitary gland, located at the base of the brain, is one of the primary examples of a gland without ducts. It considered the “master gland” of the endocrine system. Although it is only the size of a pea, it is responsible for a number of critical functions including: the production of growth hormone, aspects of pregnancy and childbirth, breast milk production, sex organ function, thyroid gland function, conversion of food to energy, and water regulation in the body.
Other glands which are traditionally classified as ductless include the thymus, thyroid, and adrenal glands. The spleen is also typically included. This large gland is used to destroy unnecessary red blood cells and functions as a part of the immune system. There are also instances of ductless glands in the gastric and intestinal mucous membranes as well.
Glands without ducts must usually rely on internal secretions to function properly. In most cases they’re able to form their necessary compounds from the materials that are brought to them via the blood supply, then they form internal passageways or cellular networks, either internally or on their surfaces. These aren’t usually considered true ducts since they aren’t enclosed, but they usually work in about the same way. Cells known as “goblet cells” are in large part responsible for the ability of the glands to secrete directly onto their surface.
Once the gland has created the target product, it is able to send that product back into the bloodstream, usually through the same means as the components entered, for transportation throughout the body. At times, the secretions can be carried by means of the lymphatic system as well.
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