Gland

Your body has tiny parts called glands.

Glands make things your body needs. They can also get rid of waste.

Some glands send things into your blood. These help your body stay well.

Other glands use small tubes. These tubes carry things to your skin.

Some glands make watery things. Other glands make thick things. Some even make oil.

Your glands are very busy workers!

Your body has special parts called glands.

Glands make things your body needs. They can also remove waste. Glands are made of many parts. Most are made of epithelial tissue. They often have a shell called a capsule.

There are two main kinds of glands. The first kind is endocrine glands. These glands do not have tubes. They let out hormones into the blood. Hormones are things that help your body stay well. The thyroid gland is one example.

The second kind is exocrine glands. These glands use a tube called a duct. The duct carries things to a surface. This could be your skin. It could also be inside your body. Some exocrine glands make watery fluid. Others make thick mucus. Some even make oil. One type is called a sebaceous gland. These make oil. If a gland gets sick, it is called adenosis. This can happen when the tissue grows in a strange way.

A gland is a special part of an animal's body. It can be a single cell or a whole organ. Glands make and release things that living things need to work. They can also help remove waste like urine. Most glands are made of epithelial tissue. They often have a layer of connective tissue for support. They also usually have a protective shell called a capsule.

Glands grow in a very interesting way. They start as a part of a surface growing inward. Sometimes they start as a simple tube shape. Other times they start as a solid column of cells. As they grow, the column might split into branches. These branches make a compound gland. Some glands like the pancreas have many branches. The branches usually do not join back together. The liver is a rare exception to this rule.

There are two main ways a gland works. The first way is through endocrine glands. These glands are ductless, which means they have no tubes. They release products called hormones into the spaces between cells. These hormones then enter the bloodstream to travel. This helps the body maintain homeostasis, or a steady balance. Examples include the pituitary, thyroid, and adrenal glands.

The second way is through exocrine glands. These glands use a tube called a duct. The duct carries substances to a surface. This could be the skin or the inside of the gut. There are three ways these cells release their products. Merocrine glands release things through a process called exocytosis. Apocrine glands lose part of the cell body during release. Holocrine glands release products when the whole cell breaks apart.

Exocrine glands make many different types of substances. Serous glands make a watery fluid that is rich in protein. Mucous glands make a thick, sticky product. Sebaceous glands are also called oil glands. They make a lipid product to help the body. If a gland develops in an abnormal way, it is called adenosis. This can sometimes lead to a tumor. Understanding glands helps us see how our bodies stay healthy.

A gland is a specialized cell or organ within an animal's body. Its primary purpose is to produce and secrete substances required by the organism. These substances can be released into the bloodstream or into a body cavity. Glands may also function to remove unwanted substances, such as urine, from the body. Most glands consist mainly of epithelial tissue. They typically possess a supporting framework made of connective tissue and a protective capsule.

Glands develop through a specific growth process starting from an epithelial surface. This surface grows inward to form the gland. Initially, this ingrowth might possess a simple tubular structure. In other cases, a gland may begin as a solid column of cells. This column then becomes tubulated as it develops. As growth continues, the cell column may split or produce offshoots. This branching process creates what is known as a compound gland.

The complexity of a gland is often defined by its branching and shape. In compound glands, the secretory epithelium forms the terminal portion of each branch. The parts of the gland that unite to form ducts are lined with less modified epithelial cells. Most gland branches do not unite with one another. The liver is a notable exception because it produces a reticulated compound gland. Glands are also classified by their physical shape. Tubular glands maintain a tube shape throughout. Alveolar or saccular glands have an enlarged secretory portion with increased lumen size.

Functionally, glands are divided into two major groups: endocrine and exocrine. The primary difference lies in how they secrete their products. Endocrine glands are ductless systems. They secrete products called hormones through a basal lamina. This basal lamina is a layer surrounding the glands. More than a million tiny blood vessels attach to this layer. These hormones enter the interstitial spaces and are taken up by the bloodstream. This process is vital for maintaining homeostasis, which is the body's steady internal balance.

Specific examples of endocrine glands include the pineal, thymus, pituitary, and thyroid glands. The two adrenal glands are also part of this endocrine group. In contrast, exocrine glands use a structure called a duct. These ducts carry secretions onto an outer surface, like the skin, or an inner surface, like the gastrointestinal tract. In exocrine glands, secretion occurs directly onto the apical surface. This method allows for the targeted delivery of substances to specific areas of the body.

Exocrine glands are further categorized by their method of secretion. Merocrine glands use a process called exocytosis to release substances. Examples include salivary glands, tear glands, and major human sweat glands. Apocrine glands involve the loss of a portion of the cell's body during secretion. While often used to describe certain sweat glands, scientists believe some may not use this exact method. Examples include mammary glands and sweat glands in the armpit or pubic region. Holocrine glands are different because the entire cell disintegrates to release its contents. Sebaceous glands, such as the meibomian glands, are examples of holocrine glands.

Exocrine glands can also be grouped by the type of product they create. Serous glands produce a watery, protein-rich fluid. Sweat glands are a common example of this type. Mucous glands secrete a viscous product that is rich in carbohydrates, such as glycoproteins. Goblet cells function this way. Sebaceous glands, also known as oil glands, secrete a lipid product. Examples include Fordyce spots. If a gland undergoes abnormal formation or development, the condition is called adenosis. This abnormal tissue can sometimes become tumorous.