Difference between revisions of "Gland" - New World Encyclopedia

From New World Encyclopedia
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Glands can be divided into two groups:
 
Glands can be divided into two groups:
 
* [[Endocrine]] glands- are glands that secrete their product directly onto a surface rather than through a duct.
 
* [[Endocrine]] glands- are glands that secrete their product directly onto a surface rather than through a duct.
−
* [[Exocrine]] glands- secrete their products via a duct, the glands in this group can be divided into three groups:
+
* [[Exocrine]] glands- secrete their products via a duct.
−
** [[Apocrine]] glands - a portion of the secreting [[cell (biology)|cell]]'s body is lost during secretion.  ''Apocrine gland'' is often used to refer to the [[sweating|apocrine sweat glands]], however it is thought that apocrine sweat glands may not be true apocrine glands as they may not use the apocrine method of secretion.
+
 
−
** [[Holocrine]] glands - the entire cell disintegrates to secrete its substances (e.g., sebaceous glands)
+
 
−
** [[Merocrine]] glands - cells secrete their substances by [[exocytosis]] (e.g., mucous and serous glands). Also called "eccrine."
+
Endocrine glands are glands that secrete their product directly into the blood rather than through a duct. This group contains the glands of the Endocrine system
 +
 
 +
'''Exocrine glands''' are [[gland]]s that secrete their products into [[duct (anatomy)|duct]]s (duct glands). They are the counterparts to [[endocrine gland]]s, which secrete their products directly into the [[blood]]stream (ductless glands). Typical exocrine glands include [[sweat gland]]s, [[salivary gland]]s, [[mammary gland]]s, and many glands of the [[digestive system]].
 +
 
 +
 
 +
 
 +
 
 +
 
 +
There are multiple ways of classifying exocrine glands:
 +
 
 +
*'''Structure'''. Exocrine glands contain a glandular portion and a duct portion, the structures of which can be used to classify the gland.
 +
** The duct portion may be branched (called ''compound'') or unbranched (called ''simple'').
 +
** The glandular portion may be tubular, [[acinus|acinar]], or may be a mix of the two (called tubuloacinar). If the glandular portion branches, then the gland is called a branched gland.
 +
*'''Method of secretion'''. Exocrine glands are named [[apocrine]], [[holocrine gland]], or [[merocrine gland]] based on how their product is secreted.
 +
**'''[[Apocrine]] glands''' - a portion of the plasma membrane buds off the cell, containing the secretion.  ''Apocrine gland'' is often used to refer to the [[apocrine sweat glands]].
 +
**'''[[Holocrine]] glands''' - the entire cell disintegrates to secrete its substance.
 +
**'''[[Merocrine]] glands''' - cells secrete their substances by [[exocytosis]]. Also called "eccrine."
 +
*Product secreted
 +
** Serous cells secrete [[protein]]s, often [[enzyme]]s. Examples include [[chief cells]] and [[Paneth cells]]
 +
** Mucous cells secrete [[mucus]]. Examples include [[Brunner's glands]], [[esophageal glands]], and [[pyloric glands]]
 +
** Mixed glands secrete both protein and mucus. Examples include the [[salivary glands]], although [[parotid gland]] is predominantly serous, and [[sublingual gland]] is predominantly mucous.
 +
 
 +
 
 +
 
 +
 
 +
* [[Apocrine]] glands - a portion of the secreting [[cell (biology)|cell]]'s body is lost during secretion.  ''Apocrine gland'' is often used to refer to the [[sweating|apocrine sweat glands]], however it is thought that apocrine sweat glands may not be true apocrine glands as they may not use the apocrine method of secretion.
 +
* [[Holocrine]] glands - the entire cell disintegrates to secrete its substances (e.g., sebaceous glands)
 +
* [[Merocrine]] glands - cells secrete their substances by [[exocytosis]] (e.g., mucous and serous glands). Also called "eccrine."
 +
 
 
The type of secretory product of an [[Exocrine]] gland may also be one of three categories:
 
The type of secretory product of an [[Exocrine]] gland may also be one of three categories:
 
* [[Serous]] glands- secrete a watery, often protein-rich product
 
* [[Serous]] glands- secrete a watery, often protein-rich product
 
* [[Mucous]] glands- secrete a viscous product, rich in carbohydrates (e.g., glycoproteins)
 
* [[Mucous]] glands- secrete a viscous product, rich in carbohydrates (e.g., glycoproteins)
 
* [[Sebaceous]] glands- secrete a lipid product
 
* [[Sebaceous]] glands- secrete a lipid product
 +
 +
 +
 +
  
 
==Formation==
 
==Formation==
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* In the second main variety of gland the secretory portion is enlarged and the [[lumen]] variously increased in size. These are termed [[alveolar gland|alveolar]] or saccular glands.
 
* In the second main variety of gland the secretory portion is enlarged and the [[lumen]] variously increased in size. These are termed [[alveolar gland|alveolar]] or saccular glands.
  
−
==Specific glands==
+
==List of glands==
−
A list of ''exocrine glands'' is available [[Exocrine_gland#List_of_exocrine_glands|here]].
+
 
 +
===Endocrine glands===
 +
 
 +
 
 +
A list of ''endocrine glands'' is available [[Endocrine_system#Major endocrine glands in human body|here]].
 +
 
 +
===Exocrine glands===
 +
 
 +
Glands typically may be referred to by two or more means, though some terms are rarely seen.  The names of the [[anatomist]]s who first described them are often employed, as:
 +
 
 +
{| class="sortable wikitable"
 +
| '''name(s)''' || '''location'''  || '''product'''  || '''structure'''
 +
|-
 +
|  [[apocrine sweat glands]]  || [[skin]]  || -  || coiled tubular
 +
|-
 +
| [[Bartholin's glands]], Tiedmann's glands, vulvovaginal glands  || [[vulva]], [[vagina]]  || -  || -
 +
|-
 +
| [[Baughin's glands]], anterior lingual glands  ||  [[tongue]], near tip  || nonserious or mixed  || -
 +
|-
 +
| [[Brunner's glands]], duodenal glands || [[duodenum]]  || mucous  || compound tubular
 +
|-
 +
| [[bulbourethral glands]], Cowper's glands, Mery's glands || [[penis]], base  || -  || -
 +
|-
 +
| [[Ciaccio's glands]], accessory [[lacrimal glands]]  || [[eye]]  || -  || -
 +
|-
 +
| [[Cobelli's glands]] || [[esophagus]], just above the [[cardia]], in the [[mucosa]]  || mucous  || -
 +
|-
 +
| [[Duverney's gland]]  || [[vagina]], on either side  || -  || -
 +
|-
 +
| [[Ebner's glands]]  || [[tongue]]  || mucous  || -
 +
|-
 +
| [[eccrine sweat glands]]  || [[skin]]  || -  || coiled tubular
 +
|-
 +
| [[esophageal glands]]  || [[esophagus]]  || mucous  || racemose
 +
|-
 +
| [[exocrine pancreas]]  || [[pancreas]]  || serous  || tubulo-acinar
 +
|-
 +
| [[Fränkel's glands]]  || [[vocal cords]], below the edge  || -  || -
 +
|-
 +
| [[gastric chief cell]], Wasmann's glands || [[stomach]]  || serous  || -
 +
|-
 +
| [[glomus coccygeum]], coccygeal gland, Luschka's gland or ganglion  || [[coccyx]], near the tip  || -  || -
 +
|-
 +
| [[goblet cells]]  || [[digestive tract]], [[respiratory tract]]  || mucous  || simple unicellular
 +
|-
 +
| [[Henle's glands]]  ||  [[eyelids]], in the [[conjuctiva]]  || -  || tubular
 +
|-
 +
| [[Huguier's glands]]  || [[vagina]] || -  || -
 +
|-
 +
| [[Krause's glands]]  || [[conjunctiva]], middle portion  || mucous  || -
 +
|-
 +
| [[Lieberkuhn's gland]]s  || [[intestines]], surface of [[mucous membrane]]  || -  || simple tubular
 +
|-
 +
| [[Littré's glands]], Morgagni's glands || [[spongy portion of the urethra]]  || -  || [[racemose]]
 +
|-
 +
| [[mammary gland]]  || [[breast]]  || - || compound tubulo-acinar
 +
|-
 +
| [[Meibomian gland]]  || [[eyelids]]  || sebaceous  || -
 +
|-
 +
| [[Moll's glands]]  || [[eyelids]]  || -  || -
 +
|-
 +
| [[Montgomery's glands]]  || mammary [[areola]]  || sebaceous  || -
 +
|-
 +
| [[Naboth's glands]]  || [[cervix]] and [[os uteri]]  || mucous  || -
 +
|-
 +
| [[olfactory glands]], Bowman's glands ||    [[nose]], [[olfactory]] region  || -  || -
 +
|-
 +
| [[Paneth cells]]  || [[small intestine]]  || serous  || -
 +
|-
 +
| [[parathyroid glands]], Gley's glands, Sandstroem's glands  || [[thyroid]], on surface  || -  || -
 +
|-
 +
| [[parotid gland]]  || [[mouth]]  || serous  || tubulo-alveolar
 +
|-
 +
| [[Peyer's patches]] (or glands) ||  [[ileum]], [[lymphatic]] glands  || -  || -
 +
|-
 +
| [[pyloric glands]]  || [[stomach]]  || mucous  || simple branched tubular
 +
|-
 +
| [[sebaceous gland]]  || [[skin]]  || sebum  || acinar - branched
 +
|-
 +
| [[Skene's glands]], Guérin's glands || [[vagina]]  || -  || -
 +
|-
 +
| [[sublingual gland]], Rivini's gland ||  [[mouth]]  || mucus (primarily) || tubulo-alveolar
 +
|-
 +
| [[submandibular gland]]  || [[mouth]]  || mixed (M+S) || tubulo-alveolar
 +
|-
 +
| [[sudoriparous glands]], Boerhaave's glands || [[skin]]  || -  || -
 +
|-
 +
| [[Sigmund's glands]]  || [[epitrochlear]] [[lymph node]]s  || -  || -
 +
|-
 +
| [[Suzanne's gland]]  || mouth, beneath the [[alveolingual]] groove  || mucous  || -
 +
|-
 +
| [[Weber's glands]]  || [[tongue]]  || mucous  || tubular
 +
|-
 +
| [[Glands of Zeis]]  || [[eyelids]], free edges  || sebaceous  || -
 +
|}
  
−
A list of ''endocrine glands'' is available [[Endocrine_system#Endocrine_glands_and_the_hormones_secreted|here]].
 
  
 
==Additional images==
 
==Additional images==
 
<gallery>
 
<gallery>
 +
Image:Gray1033.png|Section of the human esophagus. Moderately magnified.
 +
Image:Gray1172.png|Dissection of a lactating breast.
 
  Image:Gray1025.png|Section of [[submaxillary gland]] of kitten. Duct semidiagrammatic.
 
  Image:Gray1025.png|Section of [[submaxillary gland]] of kitten. Duct semidiagrammatic.
 
  Image:Gray1105.png|Section of [[pancreas]] of dog. X 250.  
 
  Image:Gray1105.png|Section of [[pancreas]] of dog. X 250.  
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*{{1911}}
 
*{{1911}}
 
{{Glands}}
 
{{Glands}}
−
[[Category:Endocrine system]]
+
 
−
[[Category:Exocrine system]]
+
{{credit|Gland|136924084|Exocrine_gland|128287538|Endocrine_glands|127535005}}
−
[[Category:Glands|*]]
 
−
{{credit|136924084}}
 
 
[[Category:Living sciences]]
 
[[Category:Living sciences]]

Revision as of 00:19, 18 June 2007

Human submaxillary gland. At the right is a group of mucous alveoli, at the left a group of serous alveoli.
For other uses, see Gland (disambiguation).

A gland is an organ in an animal's body that synthesizes a substance for release such as hormones, often into the bloodstream (endocrine gland) or into cavities inside the body or its outer surface (exocrine gland).

Types

Glands can be divided into two groups:

  • Endocrine glands- are glands that secrete their product directly onto a surface rather than through a duct.
  • Exocrine glands- secrete their products via a duct.


Endocrine glands are glands that secrete their product directly into the blood rather than through a duct. This group contains the glands of the Endocrine system

Exocrine glands are glands that secrete their products into ducts (duct glands). They are the counterparts to endocrine glands, which secrete their products directly into the bloodstream (ductless glands). Typical exocrine glands include sweat glands, salivary glands, mammary glands, and many glands of the digestive system.


There are multiple ways of classifying exocrine glands:

  • Structure. Exocrine glands contain a glandular portion and a duct portion, the structures of which can be used to classify the gland.
    • The duct portion may be branched (called compound) or unbranched (called simple).
    • The glandular portion may be tubular, acinar, or may be a mix of the two (called tubuloacinar). If the glandular portion branches, then the gland is called a branched gland.
  • Method of secretion. Exocrine glands are named apocrine, holocrine gland, or merocrine gland based on how their product is secreted.
    • Apocrine glands - a portion of the plasma membrane buds off the cell, containing the secretion. Apocrine gland is often used to refer to the apocrine sweat glands.
    • Holocrine glands - the entire cell disintegrates to secrete its substance.
    • Merocrine glands - cells secrete their substances by exocytosis. Also called "eccrine."
  • Product secreted
    • Serous cells secrete proteins, often enzymes. Examples include chief cells and Paneth cells
    • Mucous cells secrete mucus. Examples include Brunner's glands, esophageal glands, and pyloric glands
    • Mixed glands secrete both protein and mucus. Examples include the salivary glands, although parotid gland is predominantly serous, and sublingual gland is predominantly mucous.


  • Apocrine glands - a portion of the secreting cell's body is lost during secretion. Apocrine gland is often used to refer to the apocrine sweat glands, however it is thought that apocrine sweat glands may not be true apocrine glands as they may not use the apocrine method of secretion.
  • Holocrine glands - the entire cell disintegrates to secrete its substances (e.g., sebaceous glands)
  • Merocrine glands - cells secrete their substances by exocytosis (e.g., mucous and serous glands). Also called "eccrine."

The type of secretory product of an Exocrine gland may also be one of three categories:

  • Serous glands- secrete a watery, often protein-rich product
  • Mucous glands- secrete a viscous product, rich in carbohydrates (e.g., glycoproteins)
  • Sebaceous glands- secrete a lipid product


Formation

Every gland is formed by an ingrowth from an epithelial surface. This ingrowth may from 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.

  • 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 lumen variously increased in size. These are termed alveolar or saccular glands.

List of glands

Endocrine glands

A list of endocrine glands is available here.

Exocrine glands

Glands typically may be referred to by two or more means, though some terms are rarely seen. The names of the anatomists who first described them are often employed, as:

name(s) location product structure
apocrine sweat glands skin - coiled tubular
Bartholin's glands, Tiedmann's glands, vulvovaginal glands vulva, vagina - -
Baughin's glands, anterior lingual glands tongue, near tip nonserious or mixed -
Brunner's glands, duodenal glands duodenum mucous compound tubular
bulbourethral glands, Cowper's glands, Mery's glands penis, base - -
Ciaccio's glands, accessory lacrimal glands eye - -
Cobelli's glands esophagus, just above the cardia, in the mucosa mucous -
Duverney's gland vagina, on either side - -
Ebner's glands tongue mucous -
eccrine sweat glands skin - coiled tubular
esophageal glands esophagus mucous racemose
exocrine pancreas pancreas serous tubulo-acinar
Fränkel's glands vocal cords, below the edge - -
gastric chief cell, Wasmann's glands stomach serous -
glomus coccygeum, coccygeal gland, Luschka's gland or ganglion coccyx, near the tip - -
goblet cells digestive tract, respiratory tract mucous simple unicellular
Henle's glands eyelids, in the conjuctiva - tubular
Huguier's glands vagina - -
Krause's glands conjunctiva, middle portion mucous -
Lieberkuhn's glands intestines, surface of mucous membrane - simple tubular
Littré's glands, Morgagni's glands spongy portion of the urethra - racemose
mammary gland breast - compound tubulo-acinar
Meibomian gland eyelids sebaceous -
Moll's glands eyelids - -
Montgomery's glands mammary areola sebaceous -
Naboth's glands cervix and os uteri mucous -
olfactory glands, Bowman's glands nose, olfactory region - -
Paneth cells small intestine serous -
parathyroid glands, Gley's glands, Sandstroem's glands thyroid, on surface - -
parotid gland mouth serous tubulo-alveolar
Peyer's patches (or glands) ileum, lymphatic glands - -
pyloric glands stomach mucous simple branched tubular
sebaceous gland skin sebum acinar - branched
Skene's glands, Guérin's glands vagina - -
sublingual gland, Rivini's gland mouth mucus (primarily) tubulo-alveolar
submandibular gland mouth mixed (M+S) tubulo-alveolar
sudoriparous glands, Boerhaave's glands skin - -
Sigmund's glands epitrochlear lymph nodes - -
Suzanne's gland mouth, beneath the alveolingual groove mucous -
Weber's glands tongue mucous tubular
Glands of Zeis eyelids, free edges sebaceous -


Additional images

  • Section of the human esophagus. Moderately magnified.

  • Dissection of a lactating breast.

  • 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.

  • Apocrine

References
ISBN links support NWE through referral fees

  • This article incorporates text from the Encyclopædia Britannica Eleventh Edition, a publication now in the public domain.
Glands (Endocrine, Exocrine)

mechanism (Merocrine, Apocrine, Holocrine) shape (Tubular gland, Alveolar gland) secretion (Serous glands, Mucous glands, Serous demilune)

Ducts: Interlobar duct, Interlobular duct, Intralobular duct (Striated duct, Intercalated duct), Acinus

Credits

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