Gland
| Gland | |
|---|---|
 Human submandibular gland. At the right is a group of mucous acini, at the left a group of serous acini. | |
| Details | |
| Identifiers | |
| Latin | glandula |
| TH | H2.00.02.0.02002 |
| Anatomical terminology | |
In animals, a gland is a group of cells[1] in an animal's body (and used by myrmecophyte plants to feed their ant symbiotes) that synthesizes substances (such as hormones) for release into the bloodstream (endocrine gland) or into cavities inside the body or its outer surface (exocrine gland).
Structure
Development
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.[2]
As growth proceeds, the column of cells may split 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.[2]
Glands are classified according to their shape.
- If the gland retains its shape as a tube throughout it is termed a tubular gland.
- In the second main variety of gland the secretory portion is enlarged and the lumens variously increased in size. These are termed alveolar or saccular glands.[2]
Types of glands
Glands are divided based on their function into two groups:
Endocrine glands
Exocrine glands
- apocrine sweat glands, however it is thought that apocrine sweat glandsmay not be true apocrine glands as they may not use the apocrine method of secretion, e.g. mammary gland, sweat gland of arm pit, pubic region, skin around anus, lips and nipples.
- Holocrine glands – the entire cell disintegrates to secrete its substances, e.g. sebaceous glands: meibomian and zeis glands.
- eccrine", e.g. major sweat glands of humans, goblet cells, salivary gland, tear gland and intestinal glands.
The type of secretory product of exocrine glands may also be one of three categories:
- Serousglands secrete a watery, often protein-rich, fluid-like product, e.g. sweat glands.
- carbohydrates (such as glycoproteins), e.g. goblet cells.
- Sebaceous glands secrete a lipid product. These glands are also known as oil glands, e.g. Fordyce spots and meibomian glands.
Clinical significance
![[icon]](/File:Wiki_letter_w_cropped.svg){kind=small} | This section needs expansion. You can help by adding to it. (April 2014) |
Adenosis is any disease of a gland. The diseased gland has abnormal formation or development of glandular tissue which is sometimes tumorous.[3]
References
- ^ "Definition of Gland". medicinenet.com. Archived from the original on 14 December 2017. Retrieved 2 May 2018.
- ^ a b c One or more of the preceding sentences incorporates text from a publication now in the public domain: Chisholm, Hugh, ed. (1911). "Epithelial, Endothelial and Glandular Tissues". Encyclopædia Britannica. Vol. 9 (11th ed.). Cambridge University Press. pp. 705–707.
- ISBN 978-1-4160-6257-8.
External links
