||It has been suggested that Ductless gland be merged into this article. (Discuss) Proposed since January 2014.|
|Human submaxillary gland. At the right is a group of mucous alveoli, at the left a group of serous alveoli.|
A gland is an organ in an animal's body that synthesizes a substance such as hormones or breast milk for release into the bloodstream (endocrine gland) or into cavities inside the body or its outer surface (exocrine gland).
Glands can be divided into 8 groups:
The type of secretory product of an Exocrine gland may also be one of three categories:
Every gland is formed by an ingrowth from an epithelial surface. This ingrowth may in the beginning possess a tubular structure, but in other instances glands may start as a solid column of cells which subsequently becomes tubulated.
As growth proceeds, the column of cells may divide or give off offshoots, in which case a compound gland is formed. In many glands the number of branches is limited, in others (salivary, pancreas) a very large structure is finally formed by repeated growth and sub-division. As a rule, the branches do not unite with one another, but in one instance, the liver, this does occur when a reticulated compound gland is produced. In compound glands the more typical or secretory epithelium is found forming the terminal portion of each branch, and the uniting portions form ducts and are lined with a less modified type of epithelial cell.
Glands are classified according to their shape.
Section of submaxillary gland of kitten. Duct semidiagrammatic.
Section of pancreas of dog. X 250.
Dissection of a lactating breast.
Section of portion of mamma.
Methods of secretion
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