Gland

Human submaxillary gland. On the right is shown a group of mucous alveolos, on the left side of the serous alveolos.

A gland is a specialization of epithelial tissue, made up of one or more epithelial cells whose function is to secrete chemical substances, such as hormones, to release them, often into the bloodstream and in the body. interior of a body cavity or its exterior surface. These substances can be chemical messengers that are incorporated into the organism to reach the cell to which it is destined, according to its special characteristic, or directly produce a specific effect in the environment to which they are secreted.

Etymology

The word gland comes from the diminutive Latin glandulae (fem. pl., cf. Celsus 4.1) meaning "tonsils" or "glands of the throat". In turn, this term is a diminutive of glans (fem. sg., genitive glandis) which means "nut". glandulae (a plurale tantum) would literally mean "little nuts".

Classification

Site of discharge

According to their place of secretion, the glands are divided into:

• Endocrines - They are also called closed glands. They lack duct and pour their secretion into the capillaries surrounding the glands.

• Exocrines - Also called open glands. They secrete their products to an excretor tube that secretes their product on both the surface and the light of a hollow organ. This type of glands are divided into three groups according to their different mechanisms to download their secreted products:

• Apocrines - when you release your secretion product a small part of the cytoplasm of the body cells are lost. The term apocrine gland is often used to refer to sweat glands. Even so, the apocrine sweat glands, whose name comes from the old belief of their type of secretion, have a merocrine secretion that was verified by studies with the MET.
• Holocrines - the entire cell disintegrates to excrete its content, as in the sebaceous glands found in the skin's corion.
• Merocrines - cells secrete their substances by exocytosis, as in mucous and serous glands.

• Mixed - They are glands that in their structure produce, both products that are secreted to the outside and the bloodstream.

Number of cells

They can also be divided into unicellular and multicellular according to their number of cells:

• Unicellular - Individual cells that are distributed between non-secretary cells. An example is caliciform cells.
• Pluricelures - Composed of more than one cell, you can differentiate between the arrangement of secret cells and if there is or does not branch the secret ducts. Multicellular glands have a secret portion, adenum, and may have or may not have a conduit that carries the substance out.

Shape of canals

• Simple: if the gland has a single duct.
• Ramified: if the gland has several ducts.
• Budget: if the ducts are divided successively.
• Rolled: when the duct rolls over itself forming a loop.

Shape of Adenomeres

• Tubular: if the adenummer has tube shape
• Alveolar or acinar: if the adenummer is shaped like a nuance

There can also be combinations, if the adenomere has a dilated shape, the gland is tubuloalveolar or tubuloacinar.

Type of discharge

The type of secretory product of an exocrine gland can also be divided into three classes:

• Seri - aqueous product often rich in proteins.
• Mucoso - viscous product rich in carbohydrates, such as glucoproteins.
• Sebaceous - lipid product.