Difference between revisions of "AY Honors/Shells - Advanced/Answer Key"

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The '''mantle''' is an organ found in [[mollusk]]s. It is the dorsal body wall covering the main body, or visceral mass. The [[Epidermis (skin)|epidermis]] of this organ secretes [[calcium carbonate]] to create a shell.
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{{dablink|Mother of Pearl redirects here.  For the novel, see [[Mother of Pearl (novel)]]}}
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'''Nacre''', also known as '''mother of pearl''', is a naturally-occurring organic-inorganic composite.
== Shell formation ==
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[[Image:NautilusCutawayLogarithmicSpiral.jpg|thumb|right|225px|The iridescent nacre of a [[Nautilus]] ]]
  
[[Nacre]] is secreted by the [[germ layer|ectodermic]] [[cell (biology)|cells]] of the mantle tissue of most mollusks. Mollusk [[blood]] is rich in a liquid form of [[calcium]]. In these mollusks the calcium is concentrated out from the blood where it can crystallize as calcium carbonate (CaCO<sub>3</sub>). The individual crystals of each layer differ in shape and orientation. Nacre is continually deposited onto the inner surface of the animal's [[animal shell|shell]] (the [[iridescent]] ''nacreous layer'', also known as ''[[Nacre|mother of pearl]]''), both as a means to smoothen the shell itself and as a defense against [[parasite|parasitic organisms]] and damaging detritus.
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Also refers to hester the mother if pearl in scarlet letter
  
The calcium carbonate layers are generally of two types: an outer, chalk-like prismatic layer and an inner pearly, lamellar or nacreous layer. The layers may incorporate a substance called [[conchiolin]], often in order to help bind the calcium carbonate crystals together. Conchiolin is composed largely of [[quinone]]-tanned [[protein]]s.
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== Description ==
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Nacre is composed of hexagonal platelets of [[aragonite]] ([[calcium carbonate]] (CaCO<sub>3</sub>) [[crystals]]) that are 10-20 µm wide and 0.5 µm thick, arranged in a continuous parallel lamina. The layers of platelets are separated by sheets of organic matrix that are composed of [[elastic]] [[biopolymers]] (such as [[chitin]], [[lustrin]] and [[silk]]-like proteins). This mixture of brittle platelets and the thin layers of elastic biopolymers makes the material strong and resilient. Strength and resilience are also likely to be due to adhesion by the  "brickwork" arrangement of the platelets, which inhibits transverse crack propagation. This design at multiple-length sizes increases its toughness enormously, making it almost equivalent to that of [[silicon]].
  
Some shells may also contain pigments, which accounts for the fabulous colours of some [[seashell]]s. These shell pigments may include compounds like [[pyrrole]]s and [[porphyrin]]s, which are also proteins.
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The [[iridescent]] appearance of the nacre is due to the fact that the thickness of the aragonite platelets are about 0.5 micrometres, which is comparable to the wavelength of visible light. This results in constructive and destructive [[interference]] of different wavelengths of light, resulting in different colors of light being reflected at different viewing angles.  
  
== The mantle cavity ==
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Nacre is secreted by the [[epithelial]] [[cell (biology)|cells]] of the [[Mantle (mollusc)|mantle tissue]] of certain species of [[mollusk]]. In these mollusks, nacre is continually deposited onto the inner surface of the animal's shell (the [[iridescent]] ''nacreous layer'', commonly known as ''mother of pearl''), both as a means to smooth the shell itself and as a defense against [[parasite|parasitic organisms]] and damaging detritus.  
A mantle skirt is a double fold of mantle that encloses a water space. This space is called the ''mantle cavity'', and it is a central feature of mollusk biology, containing the mollusk's [[gill]]s, [[anus]], [[osphradium]], [[nephridiopore]]s, and [[gonopore]]s. The mantle cavity may function as a [[Respiration (physiology)|respiratory]] chamber (all mollusks), feeding structure ([[bivalve]]s), brood chamber (several forms), or locomotory organ ([[cephalopod]]s and some bivalves).
 
  
The mantle is highly muscular. In cephalopods it is used to force water through a tubular siphon, the [[hyponome]], to propel the animal quickly through the water. In other mollusks, it is used as a kind of "foot" for locomotion.
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The iridescent inner layer is considered highly attractive by many cultures and is often used in making [[jewelery]] or as inlays in wood [[furniture]] and [[guitar]]s.
  
The [[nervous system]] of cephalopods is the most complex of the [[invertebrate]]s. The giant [[nerve]] fibers of the cephalopod mantle have been a favorite experimental material of [[Neurophysiology|neurophysiologists]] for many years.
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When a mollusk is invaded by a [[parasite]] or is irritated by a foreign object that the animal cannot eject, a process known as ''[[encystation]]'' entombs the offending entity in successive, concentric layers of nacre. This process eventually forms what we call [[pearl]]s and continues for as long as the mollusk lives.
  
== See also ==
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Chief sources are the pearl [[oyster]], found in warm and tropical seas, primarily in [[Asia]]; freshwater pearl mussels, which live in many rivers of the [[United States]], [[Europe]], and [[Asia]]; and the [[abalone]] of [[California]], [[Japan]], and other [[Pacific Ocean|Pacific]] regions.
* [[Aperture (mollusc)|Aperture]]
 
* [[Columnella]]
 
* [[Operculum (gastropod)|Operculum]]
 
  
[[Category:Animal anatomy]]
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==Decorative uses==
[[Category:Molluscs]]
 
  
[[pt:Manto (molusco)]]
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Both black and white mother of pearl are used for architectural purposes. The natural mother of pearl may be artificially tinted to almost any color.
[[ru:Мантия моллюсков]]
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Mother of pearl is also used to clad porcelain sinks. Mother of pearl tesserae may be cut into artistic shapes and be laminated to ceramic tile and surrounded by numerous coats of colored lacquer to create an artistic design. The lacquer and the mother of pearl are polished at the same time, creating a durable, glossy hard surface.
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It is also available in thin laminated sheet form, allowing easy inlay and cladding work, and modern ceramic tiles.
 +
 
 +
Shirt buttons were once often made of mother of pearl, though plastic has largely replaced its use.  Some of the finer-quality clothing companies (e.g., [[Lacoste (company)|Lacoste]] and [[Turnbull & Asser (company)|Turnbull & Asser]]) still use it, however.
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 +
Mother of pearl is a popular style watch dial also found in [[Rolex]] watches.
 +
 
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Key touches and various decorations on musical instruments such as [[saxophone]]s, [[trumpet]]s, [[violin]]s and [[guitar]]s are sometimes made of mother of pearl.  Synthetic key touches made of [[Pyralin]] or similar imitation materials have been "affectionately" referred to as ''mother of toilet seat'' by musicians.
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===Tiles===
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Small, hand-cut shapes with straight edges, called 'tesserae', are laminated to either a [[marble]] or a [[ceramic]] base. The tesserae are hand-placed and closely sandwiched together, creating an irregular mosaic or pattern (such as a weave). The laminated material is typically 1/16 of an inch thick.
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===Sheets===
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Instead of using a marble or tile base, the mother of pearl tesserae are glued to a [[fiberglass]] mesh. The result is a lightweight material that offers a seamless installation, and there is no limit to the sheet size. Mother of pearl sheets may be used on interior floors, exterior and interior walls, countertops, doors and ceilings. Insertion into architectural elements, such as columns or furniture is easily accomplished.
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==Gallery==
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<gallery>
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image:nacre.jpg|A piece of nacre
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image:Nacre_microscopic_structure.png|Microscopic structure of nacre—layers of aragonite platelets are separated by protein
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Image:HoloscaphitesAmmonite.jpg|[[Fossilized]] [[Ammonite]] with nacre shell intact
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</gallery>
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==References==
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*Lin, A., and Meyers, M.A. (2005). Growth and structure in abalone shell, ''Materials Science and Engineering A'' '''390'''(Jan. 15):27&ndash;41 ([http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6TXD-4DH2DRS-1&_coverDate=01%2F15%2F2005&_alid=256050522&_rdoc=1&_fmt=&_orig=search&_qd=1&_cdi=5588&_sort=d&view=c&_acct=C000050221&_version=1&_urlVersion=0&_userid=10&md5=f4efd0a3d7cf3b4a0b8f9861cff4514d ])
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*Mayer, G. (2005). [http://www.sciencemag.org/cgi/content/abstract/310/5751/1144 Rigid biological systems as models for synthetic composites]. ''Science'' '''310''':1144&ndash;1147
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*{{cite journal | quotes=no|author = Ortiz C. ''et al.''|year=September 2005|title = Nanoscale morphology and indentation of individual nacre tablets from the gastropod mollusc ''Trochus niloticus''|journal= J. Mater. Res.|volume= 20|issue=9}} [http://web.mit.edu/cortiz/www/Ben/BenPaperRevisedFinal.pdf  pdf file on line]
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==See also==
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{{Wiktionary}}
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* [[Ammolite]]
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[[Category:Mollusc products]]
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[[Category:Pearls]]
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[[de:Perlmutt]]
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[[es:Nácar]]
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[[fr:Nacre]]
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[[nl:Parelmoer]]
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[[pl:Masa perłowa]]
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[[pt:Madrepérola]]
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[[sv:Pärlemor]]
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[[tr:Sedef]]
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[[vi:Xà cừ (vật liệu)]]

Revision as of 04:53, 8 November 2006

Template:Dablink Nacre, also known as mother of pearl, is a naturally-occurring organic-inorganic composite.

The iridescent nacre of a Nautilus

Also refers to hester the mother if pearl in scarlet letter

Description

Nacre is composed of hexagonal platelets of aragonite (calcium carbonate (CaCO3) crystals) that are 10-20 µm wide and 0.5 µm thick, arranged in a continuous parallel lamina. The layers of platelets are separated by sheets of organic matrix that are composed of elastic biopolymers (such as chitin, lustrin and silk-like proteins). This mixture of brittle platelets and the thin layers of elastic biopolymers makes the material strong and resilient. Strength and resilience are also likely to be due to adhesion by the "brickwork" arrangement of the platelets, which inhibits transverse crack propagation. This design at multiple-length sizes increases its toughness enormously, making it almost equivalent to that of silicon.

The iridescent appearance of the nacre is due to the fact that the thickness of the aragonite platelets are about 0.5 micrometres, which is comparable to the wavelength of visible light. This results in constructive and destructive interference of different wavelengths of light, resulting in different colors of light being reflected at different viewing angles.

Nacre is secreted by the epithelial cells of the mantle tissue of certain species of mollusk. In these mollusks, nacre is continually deposited onto the inner surface of the animal's shell (the iridescent nacreous layer, commonly known as mother of pearl), both as a means to smooth the shell itself and as a defense against parasitic organisms and damaging detritus.

The iridescent inner layer is considered highly attractive by many cultures and is often used in making jewelery or as inlays in wood furniture and guitars.

When a mollusk is invaded by a parasite or is irritated by a foreign object that the animal cannot eject, a process known as encystation entombs the offending entity in successive, concentric layers of nacre. This process eventually forms what we call pearls and continues for as long as the mollusk lives.

Chief sources are the pearl oyster, found in warm and tropical seas, primarily in Asia; freshwater pearl mussels, which live in many rivers of the United States, Europe, and Asia; and the abalone of California, Japan, and other Pacific regions.

Decorative uses

Both black and white mother of pearl are used for architectural purposes. The natural mother of pearl may be artificially tinted to almost any color.

Mother of pearl is also used to clad porcelain sinks. Mother of pearl tesserae may be cut into artistic shapes and be laminated to ceramic tile and surrounded by numerous coats of colored lacquer to create an artistic design. The lacquer and the mother of pearl are polished at the same time, creating a durable, glossy hard surface.

It is also available in thin laminated sheet form, allowing easy inlay and cladding work, and modern ceramic tiles.

Shirt buttons were once often made of mother of pearl, though plastic has largely replaced its use. Some of the finer-quality clothing companies (e.g., Lacoste and Turnbull & Asser) still use it, however.

Mother of pearl is a popular style watch dial also found in Rolex watches.

Key touches and various decorations on musical instruments such as saxophones, trumpets, violins and guitars are sometimes made of mother of pearl. Synthetic key touches made of Pyralin or similar imitation materials have been "affectionately" referred to as mother of toilet seat by musicians.

Tiles

Small, hand-cut shapes with straight edges, called 'tesserae', are laminated to either a marble or a ceramic base. The tesserae are hand-placed and closely sandwiched together, creating an irregular mosaic or pattern (such as a weave). The laminated material is typically 1/16 of an inch thick.

Sheets

Instead of using a marble or tile base, the mother of pearl tesserae are glued to a fiberglass mesh. The result is a lightweight material that offers a seamless installation, and there is no limit to the sheet size. Mother of pearl sheets may be used on interior floors, exterior and interior walls, countertops, doors and ceilings. Insertion into architectural elements, such as columns or furniture is easily accomplished.

Gallery

References

See also

Template:Wiktionary

de:Perlmutt es:Nácar fr:Nacre nl:Parelmoer pl:Masa perłowa pt:Madrepérola sv:Pärlemor tr:Sedef vi:Xà cừ (vật liệu)