The esophageal glands are glands that are part of the digestive system of various animals, including humans.
In humans
Esophageal glands in humans are a part of a
human digestive system
The human digestive system consists of the gastrointestinal tract plus the accessory organs of digestion (the tongue, salivary glands, pancreas, liver, and gallbladder). Digestion involves the breakdown of food into smaller and smaller compone ...
. They are a small compound
racemose
A raceme ( or ) or racemoid is an unbranched, indeterminate type of inflorescence bearing flowers having short floral stalks along the shoots that bear the flowers. The oldest flowers grow close to the base and new flowers are produced as the s ...
exocrine glands
Exocrine glands are glands that secrete substances on to an epithelial surface by way of a duct. Examples of exocrine glands include sweat, salivary, mammary, ceruminous, lacrimal, sebaceous, prostate and mucous. Exocrine glands are one of two ...
of the
mucous
Mucus ( ) is a slippery aqueous secretion produced by, and covering, mucous membranes. It is typically produced from cells found in mucous glands, although it may also originate from mixed glands, which contain both serous and mucous cells. It is ...
type.
There are two types:
* Esophageal glands proper- mucous glands located in the submucosa. They are compound tubulo-alveolar glands. Some serous cells are present. These glands are more numerous in the upper third of the esophagus.
They secrete acid mucin for lubrication.
* Esophageal cardiac glands- mucous glands located near the cardiac orifice (esophago-gastric junction) in the lamina propria mucosae. They secrete neutral mucin
that protects the esophagus from acidic gastric juices. They are simple tubular or branched tubular glands.
* There are also mucous glands present at the pharyngo-esophageal junction in the lamina propria mucosae. These are simple tubular or branched tubular glands.
Each opens upon the surface by a long excretory
duct.
In monoplacophorans
Oesophageal gland is enlarged in large
monoplacophora
Monoplacophora , meaning "bearing one plate", is a polyphyletic superclass of molluscs with a cap-like shell inhabiting deep sea environments . Extant representatives were not recognized as such until 1952; previously they were known only from ...
n species.
In gastropods
Oesophageal gland or oesophageal pouch is a part of the
digestive system of some gastropods. Oesophageal gland or pouch is a common feature in so-called basal gastropod clades, including
Patelloidea
Patelloidea is a taxonomic superfamily of sea snails or true limpets, marine gastropod molluscs in the subclass PatellogastropodaWoRMS (2020). Patelloidea Rafinesque, 1815. Accessed at: http://www.marinespecies.org/aphia.php?p=taxdetails&id=1 ...
,
Vetigastropoda
Vetigastropoda is a major Taxonomy (biology), taxonomic group of sea snails, marine (ocean), marine gastropod mollusc, mollusks that form a very ancient lineage (evolution), lineage. Taxonomically the Vetigastropoda are sometimes treated as an O ...
,
Cocculiniformia
The Cocculinoidea is a superfamily of deepwater limpets (marine gastropods), the only superfamily in the order Cocculinida , one of the main orders of gastropods according to the taxonomy as set up by ( Bouchet & Rocroi, 2005). The clade Coccil ...
,
Neritimorpha
Neritimorpha is a taxonomic grouping, an unranked major clade of snails, gastropod mollusks. This grouping includes land snails, sea snails, slugs, some deepwater limpets, and also freshwater snails. Neritimorpha contains around 2,000 extant s ...
and
Neomphalina
Neomphaloidea is a superfamily of deep-sea snails or limpets, marine gastropod mollusks. Neomphaloidea is the only superfamily in the order Neomphalida.
The order Neomphalida has the largest ''in situ'' radiation in hydrothermal vent habitats. ...
.
The size of oesophageal gland of
scaly-foot gastropod
''Chrysomallon squamiferum'', commonly known as the scaly-foot gastropod, scaly-foot snail, sea pangolin, or volcano snail is a species of deep-sea hydrothermal-vent snail, a marine gastropod mollusc in the family Peltospiridae. This vent-e ...
''Chrysomallon squamiferum'' (family
Peltospiridae
Peltospiridae is a small family of gastropods that used to belong to the clade Vetigastropoda (according to the taxonomy of the Gastropoda by Bouchet & Rocroi, 2005), but is now included in the clade NeomphalinaBouchet, P.; Gofas, S. (2010). Pel ...
within Neomphalina) is about two orders of magnitude over the usual size.
The scaly-foot gastropod houses endosymbiotic Bacteria in the oesophageal gland.
''Chrysomallon squamiferum'' was thought to be the only species of Peltospiridae, that has enlarged oesophageal gland, but later it was shown that both species ''
Gigantopelta'' has the oesophageal gland also enlarged.
In other peltospirids, the posterior portion of the oesophagus forms a pair of blind mid-oesophageal pouches or gutters extending only to the anterior end of the foot (''
Rhynchopelta
''Rhynchopelta'' is a genus of sea snails, marine gastropod mollusks in the family Peltospiridae.
Species
Species within the genus ''Rhynchopelta'' include:
* ''Rhynchopelta concentrica
''Rhynchopelta concentrica'' is a species of sea snail ...
'', ''
Peltospira'', ''
Nodopelta'', ''
Echinopelta'', ''
Pachydermia'').
The same situation is in ''
Melanodrymia
''Melanodrymia'' is a genus of sea snails, marine gastropod mollusks in the family Melanodrymiidae.
Species
Species within the genus ''Melanodrymia'' include:
* ''Melanodrymia aurantiaca'' Hickman, 1984
* ''Melanodrymia brightae'' Warén & Bouch ...
'' within the family
Melanodrymiidae
Melanodrymiidae is a family of gastropods belonging to the superfamily Neomphaloidea.Bouchet, P. (2011). Melanodrymiidae. Accessed through: World Register of Marine Species at http://www.marinespecies.org/aphia.php?p=taxdetails&id=411613 on 2012- ...
.
and
Lepetellidae
Lepetellidae is a taxonomic family of small deepwater sea snails or limpets, marine gastropod molluscs in the superfamily Lepetelloidea in the clade Vetigastropoda (according to the taxonomy of the Gastropoda by Bouchet & Rocroi, 2005). (It was ...
are also known to have enlarged oesophageal pouches, however, though not to the extent of ''Chrysomallon''.
Both are known to house endosymbiotic bacteria, in the case of bathyphytophilids most likely also in the oesophageal glands but in the lepetellids the endosymbionts are spread in the
haemocoel
The blood circulatory system is a system of organs that includes the heart, blood vessels, and blood which is circulated throughout the entire body of a human or other vertebrate. It includes the cardiovascular system, or vascular system, tha ...
.
References
.
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External links
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Digestive system
Glands