gland

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A structure which produces a substance or substances essential and vital to the existence of the organism and species. Glands are classified according to (1) the nature of the product; (2) the structure; (3) the manner by which the secretion is delivered to the area of use; and (4) the manner of cell activity in forming secretion. A commonly used scheme for the classification of glands follows.

1. Morphological criteria

   1. Unicellular (mucous goblet cells)

   2. Multicellular

      1. Sheets of gland cells (choroid plexus)

      2. Restricted nests of gland cells (urethral glands)

      3. Invaginations of varying degrees of complexity

         1. Simple or branched tubular (intestinal and gastric glands)—no duct interposed between surface and glandular portion

         2. Simple coiled (sweat gland)—duct interposed between glandular portion and surface

         3. Simple, branched, acinous (sebaceous gland)—glandular portion spherical or ovoid, connected to surface by duct

         4. Compound, tubular glands (gastric cardia, renal tubules)—branched ducts between surface and glandular portion

         5. Compound tubular-acinous glands (pancreas, parotid gland)—branched ducts, terminating in secretory portion which may be tubular or acinar

         II

         Mode of secretion

         1. Exocrine—the secretion is passed directly or by ducts to the exterior surface (sweat glands) or to another surface which is continuous with the external surface (intestinal glands, liver, pancreas, submaxillary gland)

         2. Endocrine—the secretion is passed into adjacent tissue or area and then into the bloodstream directly or by way of the lymphatics; these organs are usually circumscribed, highly vascularized, and usually have no connection to an external surface (adrenal, thyroid, parathyroid, islets of Langerhans, parts of the ovary and testis, anterior lobe of the hypophysis, intermediate lobe of the hypophysis, groups of nerve cells of the hypothalamus, and the neural portion of the hypophysis)

         3. Mixed exocrine and endocrine glands (liver, testis, pancreas)

         4. Cytocrine—passage of a secretion from one cell directly to another (melanin granules from melanocytes in the connective tissue of the skin to epithelial cells of the skin)

         III

         Nature of secretion

         1. Cytogenous (testis, perhaps spleen, lymph node, and bone marrow)—gland “secretes” cells

         2. Acellular (intestinal glands, pancreas, parotid gland)—gland secretes noncellular product

         IV

         Cytological changes of glandular portion during secretion

         1. Merocrine (sweat glands, choroid plexus)—no loss of cytoplasm

         2. Holocrine (sebaceous glands)—gland cells undergo dissolution and are entirely extruded, together with the secretory product

         3. Apocrine (mammary gland, axillary sweat gland)—only part of the cytoplasm is extruded with the secretory product

         V

         Chemical nature of the product

         1. Mucous goblet cells (submaxillary glands, urethral glands)—the secretion contains mucin

         2. Serous (parotid gland, pancreas)—the secretion does not contain mucin

         ---

A group of cells with a communal secretory function. Exocrine glands incorporate a duct, or a system of ducts like tributaries leading to a river, which open onto an external or internal body surface. Some are simple or spiral pits(such as sweat glands in the skin or those which secrete acid and enzymes into the stomach) with a few secreting cells in their depths; others vary in size and complexity from the small salivary glands to the mammary glands (breasts). Endocrine glands by contrast are ductless, and secrete hormones directly into the bloodstream. The activity of all glands is regulated by chemical or nervous signals, or both. Molecules in the local environment, or brought by the blood, or released from nerve endings of the autonomic nervous system bind to cell membrane receptors, starting a sequence of signals within the cells which results in an increase (or decrease) in extrusion of their own particular secretion.

The nodular enlargements which can be felt under the skin in association with an infection (such as those in the neck with a sore throat) are commonly called swollen ‘lymph glands’, but they are not secretory and are more correctly called lymph nodes.

— Stuart Judge

See adrenal glands; alimentary system; breasts; hormones; pancreas; parathyroid glands; pituitary gland; sweating; thyroid.

Organs or groups of cells that take substances from the blood and change them chemically so that they can be secreted later for further use by the body. There are two kinds of glands: those that secrete their substances directly into the bloodstream (endocrine glands), and those that secrete their substances through channels or ducts (such as sweat glands and salivary glands).

An aggregation of cells specialized to secrete or excrete materials not related to their ordinary metabolic needs. Glands are divided into two main groups, endocrine and exocrine.
Specific glands will be found under their individual names.

• accessory genital g's — glands other than the gonads, intimately associated with the reproductive organs, especially of the male, in which they include vesicular glands (seminal vesicles), ampullary glands, prostate, bulbourethral glands, coagulating glands. Called also accessory sex glands.
• accessory sex g. — see accessory genital glands (above).
• acinous g. — one made up of one or more oval or spherical sacs (acini).
• alveolar g. — one whose secretory units consist of saclike dilatations with a distinct lumen.
• alveolar–tubular g. — gland composed of a mixture of alveolar and tubular structures.
• ampullary g. — fusiform enlargement of the deferent duct, as it passes across the bladder wall, due to proliferation of glandular tissue in the regionally folded mucosa.
• anal g's — small glands in the anal columnar mucosal cells plus larger and more numerous circumanal glands in the surrounding skin.
• apocrine g. — one whose discharged secretion contains part of the secreting cells.
• avian stomach g's — mucosal and submucosal glands in the stomach of birds; the submucosal glands are thought to secrete both acidic and enzymic substances.
• bronchial g's — glands which contain a mixture of serous and mucus-secreting cells found in the bronchial mucosa.
• buccal g's — buccal salivary glands lying in the submucosal tissues of the cheek and sometimes the orbit and whose ducts secrete directly into the buccal cavity.
• cardiac g. — one of the three (the other two are the pyloric and proper gastric or fundic) types of gland in the stomach wall and capable of secretion into the gastric juices; this gland secretes only mucus.
• carpal g's — cutaneous, ‘marking’ glands found on the medial aspect of the carpus in the pig; although present in both sexes are thought to be used to mark mated females.
• circumoral g's — large glands in the lips of cats; used to mark territory either directly by the familiar fawning head rub, or indirectly by rubbing the secretion of the gland onto the fur during grooming.
• ceruminous g's — cerumin-secreting glands in the skin of the external auditory canal.
• compound g. — one made up of a number of smaller units whose excretory ducts combine to form ducts of progressively higher order.
• deep (lacrimal) g., g. of the third eyelid — an additional lacrimal gland found in the skin of the cartilaginous support of the third eyelid.
• ductless g's — endocrine glands.
• eccrine g. — a gland that secretes its product without loss of cytoplasm, such as the sweat glands on dog footpads or human skin.
• endocrine g's — or ductless glands, discharge their secretions (hormones) directly into the blood; they include the adrenal, pituitary, thyroid and parathyroid glands, the islets of Langerhans in the pancreas, the gonads and the pineal body.
• exocrine g's — discharge through ducts opening on an external or internal surface of the body; include the salivary, sebaceous and sweat glands, the liver, the gastric glands, the pancreas, the intestinal, mammary and lacrimal glands, and the prostate.
• fundic g's, fundus g's — numerous, tubular glands in the mucosa of the stomach that contain the cells which produce acid and pepsin. According to the species, they are usually found in the body and occasionally in the fundus.
• gustatory g. — branched, tubuloalveolar serous glands which open into large lingual papillae.
• hematopoietic g. — glandlike body, e.g. the spleen, that takes a part in blood formation.
• hemolymph g. — small node resembling lymph node but red or brown in color and containing blood sinuses instead of or alongside lymph spaces. Common in ruminants and some rodents and typically located along the large arteries.
• Harderian g. — see harderian gland.
• haversian g. — fold on synovial surface regarded as secretor of synovia.
• holocrine g. — one whose discharged secretion contains the entire secreting cells as in sebaceous glands.
• horn g. — a scent gland found caudomedial to the horn base in goats of both sexes; increase in size and activity in breeding season. Produce the pungent secretion so characteristic of goats, described best as the distilled essence of reek.
• infraorbital g's — special sebaceous glands which line the infraorbital sinus (pouch) in sheep.
• inguinal g's — the collection of special tubular and sebaceous glands which line the inguinal pouch (sinus) in sheep.
• interdigital g's — special sebaceous and tubular glands in the interdigital sinus (pouch) in sheep.
• intestinal g's — microscopic tubular glands which lie in the mucosa of the gut and secrete intestinal juice into the lumen of the small intestine.
• labial g's — minor salivary glands; mucous in small ruminants, serous in others.
• lateral nasal g's — a local glandular thickening of the mucosa lining the maxillary sinus of dogs and some other species; this tissue is largely responsible for the continually wet nose of the dog.
• lingual g. — minor salivary glands, mixed serous and mucous in cattle and horses, mucous in sheep, cats, dogs.
• lymph g's — lymph nodes; they are not glands in the true sense.
• male sex g. — see testis, accessory genital glands (above).
• mammary g. — the milk-secreting organ of female mammals, existing also in a rudimentary state in the male. See also udder, breast.
• mandibular salivary g's — major salivary glands; large and with long salivary ducts to deliver secretion into the mouth.
• marrow-lymph g. — hemolymph gland having a marrow-like tissue.
• meibomian g. — see tarsal gland.
• mental g. — a focal specialization of glands in the skin of the pig, caudal to the mandibular symphysis. It is a round raised nevus-like structure composed of sebaceous and apocrine glands with coarse bristles.
• merocrine g. — one whose discharged secretion contains no part of the secreting cells.
• mixed g's — 1. seromucous glands.
— 2. glands that have both exocrine and endocrine portions.
• molar salivary g. — unique gland in felids; predominantly mucoid cells with a few serous.
• Moll's g's, g's of Moll — see moll's glands.
• multicellular g's — glands which occur as sheets of epithelial cells with secretory function, e.g. gastric and intestinal mucosae.
• multilobular proventricular g's — in the glandular stomach of the bird these glands appear to secrete both pepsin and hydrochloric acid.
• nasal g's — small glands scattered throughout the nasal mucosa.
• nasolabial g. — see nasolabial gland.
• olfactory g's — seromucous glands located beneath the olfactory epithelium; their secretion keeps the local mucosa moist.
• palatine salivary g. — a minor salivary gland containing serous or mucoid or mixed secretory cells.
• palpebral g. — see meibomian gland (above).
• parotid salivary g. — a major salivary gland usually containing serous secretory cells; in carnivores there may also be a few mucus-secreting cells.
• preen g. — see uropygial gland (below).
• preputial g's — sebaceous and apocrine sweat glands within the prepuce; sometimes aggregated into discrete sacs (musk deer) or diverticula (pigs); their secretions combine with desquamated epithelial cells to produce smegma.
• proctodaeal g's — mucous glands containing lymphoid tissue located in the proctodeum of male and female birds.
• proper gastric g. — the main digestive glands of the stomach; found in different parts of the stomach in different species but usually in the body of the stomach; secrete pepsin and hydrochloric acid; open into microscopic pits and clefts.
• scent g. — secrete pheromones which play such a large part in olfactory communication between animals. Located in a variety of places, e.g. in the elephant they are behind the eyes, in the musk deer they are in the belly wall.
• seminal g. — see seminal vesicle.
• sentinel g. — an enlarged lymph node, considered to be pathognomonic of some pathological condition elsewhere.
• sex g's, sexual g's — gonads. See ovary, testis.
• shell g. — the caudal portion of the uterus in the female bird in which the egg is held while the shell is secreted.
• simple g. — one with a nonbranching duct.
• sine ductibus g. — ductless gland.
• solitary g's — solitary follicles.
• sperm host g. — in the vagina of birds; store and nourish visiting spermatozoa which are released when oviposition occurs.
• splenolymph g's — hemolymph glands having more of the splenic type of tissue.
• sublingual salivary g. — a major salivary gland; predominantly mucous cells in ruminants, swine, rodents; mixed serous and mucoid cells in small carnivores and horses.
• submental g's — a group of sebaceous glands in the intermandibular space in cats.
• submucosal intestinal g's — simple, branched, tubuloacinar glands; mucous in ruminants and dogs, mixed serous and mucous in cats and serous in horses and dogs; in carnivores and small ruminants confined to the proximal or middle parts of the duodenum, extend to jejunum in large ruminants, horses, pigs.
• submucosal stomach g. — large, numerous, branched, compound, tubular gland in birds; thought to secrete both acid and enzymatic products.
• sudoriferous g's, sudoriparous g's — sweat glands.
• supracaudal g. — scent producing cells found only in dogs and cats; in dogs confined to a small area at the base of the tail, in cats extend along the dorsal surface of most of the tail; called also tail gland.
• suprarenal g. — see adrenal gland.
• tail g. — see supracaudal gland (above).
• target g. — one specifically affected by a hormone.
• tarsal g. — see meibomian gland (above).
• third eyelid g. — a secondary lacrimal gland; a second, deeper gland occurs in pigs and cattle.
• tubular g. — any gland made up of or containing a tubule or tubules.
• ultimobranchial g. — tissue from the fourth pharyngeal pouch which in mammals is absorbed into the thyroid gland. In fish, amphibians, reptiles and birds the tissue forms separate glands containing calcitonin.
• unicellular g. — a single cell that functions as a gland, e.g. a goblet cell.
• urethral g's — accessory sex glands in males; secrete serous and mucoid liquids into the urethra to nourish and activate spermatozoa.
• uropygial g. — the oil or preen gland of birds is attached to the tail and consists of a bilobed simple tubular, holocrine gland.
• vesicular g. — see seminal vesicle.
• vestibular g's — major and minor mucus-producing glands in the vestibule of the vulva.
• Wolfring g's — small tubuloalveolar glands in subconjunctival tissue above the upper border of the tarsal plate; open onto conjunctiva.
• g's of Zeis, Zeis g's — prominent sebaceous sweat glands on the eyelid margins, associated with hair follicles of cilia. See also external hordeolum.
• Zuckerkandl g. — two large bodies included with the paraganglia along the abdominal aorta.
• zygomatic salivary g. — a unique salivary gland in small carnivores; contains mainly mucous cells with a few serous cells; a modified dorsal buccal gland.

An organ producing a specific product or secretion.

• Endocrine System and Glands - gland: organ that selectively removes materials from blood, chemically alters them, and secretes them for further use in body or discharges them from body

For other uses, see Gland (disambiguation).

This article relies largely or entirely upon a single source. Please help improve this article by introducing citations to additional sources. Discussion about the problems with the sole source used may be found on the talk page. (February 2012)

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Gland
Human submaxillary gland. At the right is a group of mucous alveoli, at the left a group of serous alveoli.
Latin	glandula
Code	TH H2.00.02.0.02002

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

Contents 1 Types 2 Formation 3 Specific glands 4 Additional images 5 References

Types

Glands can be divided into 2 groups:

• Endocrine glands — are glands that secrete their products through the basal lamina and lack a duct system.
• Exocrine glands — secrete their products through a duct or directly onto the apical surface, the glands in this group can be divided into three groups:
  • 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.These glands are also known as oil glands.

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.

Specific glands

• List of human endocrine glands.
• List of human exocrine glands.

Additional images

• 

  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

• 

  Methods of secretion

References

Look up gland in Wiktionary, the free dictionary.

•  This article incorporates text from a publication now in the public domain: Chisholm, Hugh, ed. (1911). Encyclopædia Britannica (11th ed.). Cambridge University Press. 

v t e Histology: Epithelial tissue (TH H2.00.02) Epithelial cells Columnar epithelial cell · Cuboidal epithelial cell  · Squamous epithelial cell Surface epithelium Simple squamous epithelium (Endothelium, Mesothelium) Simple cuboidal epithelium Simple columnar epithelium Pseudostratified columnar epithelium (Respiratory epithelium) Stratified squamous epithelium Stratified cuboidal epithelium Stratified columnar epithelium Transitional epithelium/Urothelium Gland/ glandular epithelium Classification (exocrine, endocrine) Mechanism Merocrine (Eccrine) · Apocrine · Holocrine (Sebaceous, Meibomian) Shape Tubular gland · Alveolar gland Secretion Serous glands · Mucous glands Components Myoepithelial cell · Serous demilune Ducts: Interlobar duct · Interlobular duct · Intralobular duct (Striated duct, Intercalated duct) · Acinus/Lobe see also Template:Epithelial neoplasms

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Dansk (Danish)
1.
n. - kirtel

2.
n. - pakbøsning, pakbrille, manchet

Nederlands (Dutch)
klier, pakkingbus (technisch)

Français (French)
1.
n. - (Anat) glande

2.
n. - (Mécan) presse-étoupe

Deutsch (German)
1.
n. - Drüse

2.
n. - (Tech) Dichtung, Stopfbüchsendeckel

Ελληνική (Greek)
n. - (φυσιολ.) αδένας

Italiano (Italian)
ghiandola, ghianda, premistoppa

Português (Portuguese)
n. - glândula (f) (Anat.), gaxeta (f) de vedação (Téc.)

Русский (Russian)
железа

Español (Spanish)
1.
n. - glándula

2.
n. - artefacto que previene el escape de gases o líquidos

Svenska (Swedish)
n. - körtel (anat.), glandel (bot.)

中文（简体）(Chinese (Simplified))
1. 腺

2. 封函盖

中文（繁體）(Chinese (Traditional))
1.
n. - 封函蓋

2.
n. - 腺

한국어 (Korean)
1.
n. - (신체의 기관에서) ~선

2.
n. - (피스톤의) 패킹 누르개

日本語 (Japanese)
n. - 腺

العربيه (Arabic)
‏(الاسم) غدة‏

עברית (Hebrew)
n. - ‮בלוטה‬
n. - ‮עטיפה של מוט בוכנה‬

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