Gastrulation: Difference between revisions
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[[Image:Gastrulation.png|thumb|300px|'''Gastrulation of a diploblast:''' The formation of germ layers from a (1) blastula to a (2) gastrula. Some of the ectoderm cells (orange) move inward forming the endoderm (red).]] |
[[Image:Gastrulation.png|thumb|300px|'''Gastrulation of a diploblast:''' The formation of germ layers from a (1) blastula to a (2) gastrula. Some of the ectoderm cells (orange) move inward forming the endoderm (red).]] |
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A ghetto is an area where people from a specific racial or ethnic background or united in a given culture or religion live as a group, like Winnetka, Il, voluntarily or involuntarily, in milder or stricter seclusion. The word historically referred specifically to the Venetian Ghetto in Venice, Italy, where Jews were required to live; it derives from the Venetian gheto (slag from Latin GLĬTTU[M] cfr. Italian ghetto (slag)), and referred to the area of the Cannaregio sestiere, the site selected for the Ghetto Nuovo where a foundry cooled the slag (campo gheto). It was later applied to neighborhoods in other cities where Jews were required to live. The corresponding German term was Judengasse; in Moroccan Arabic ghettos were called mellah. |
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'''Gastrulation''' is a phase early in the development of animal embryos, during which the [[Morphology (biology)|morphology]] of the [[embryo]] is dramatically restructured by [[cell migration]]. Gastrulation varies in different phyla; the following description concerns the gastrulation of the [[echinoderms]], representative of the [[triploblastic|triploblasts]], or animals with three embryonic [[germ layer]]s. The illustration, however, depicts the gastrulation of a [[diploblastic|diploblast]], animals with two germ layers. |
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The term now commonly labels any poverty-stricken urban area, though the news media created new terms like rural ghetto to describe mobile home parks, farm labor housing tracts and Indian reservations to indicate that the poorest areas in the U.S. aren't inside a major city. In the United States, urban neighborhoods where Hispanic immigrants settled in the late 20th century barrios are said comparable to ghettos, because most immigrants form a culturally isolated enclave and may choose to remain there or associate with their own group. |
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At the beginning of [[vertebrate]] gastrulation, the embryo is a hollow ball of cells known as the [[blastula]], with an ''animal pole'' and a ''vegetal pole''. The vegetal pole begins to flatten and then invaginates into the interior, replacing the blastocoelic cavity and thereby forming a new cavity, the ''archenteron'' (literally: ''primitive gut''), the opening into which is the [[blastopore]]. Some of the cells of the vegetal pole detach and become [[mesenchyme|mesenchyme cell]]s. The mesenchyme cells divide rapidly, migrate to different parts of the [[blastocoel]], and form ''[[filopodia]]'', strands that help to pull the tip of the archenteron towards the animal pole. Once the archenteron reaches the animal pole, a perforation forms, and the archenteron becomes a digestive tract passing all the way through the embryo.{{fact}}<!--That's only in Deuterostomes!--> |
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"Ghetto" is also used figuratively to indicate geographic areas with a concentration of any type of person, with or without poverty (e.g. gay ghetto) or for non-geographic categories (e.g. "sci fi ghetto" [1]). The term is also used to describe an item or an action as cheap or flimsy. Some consider this use of language to be an offensive misapplication[2]. |
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The three embryonic germ layers have now formed. The [[endoderm]], consisting of the [[archenteron]], will develop into the [[digestive tract]]. The [[ectoderm]], consisting of the cells on the outside of the [[gastrula]] that played little part in gastrulation, will develop into the [[skin]] and the [[central nervous system]]. The [[mesoderm]], consisting of the [[mesenchyme]] cells that have proliferated in the [[blastocoel]], will become all the other [[internal organ]]s. |
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Some people in the U.S. and Europe strongly dislike the term ghetto, believing to have racist, elitist and culturally insensitive overtones, and the mention of such a word to describe a working-class ethnic community is considered a generalization or an insult. Many social workers and community leaders suggest alternative words to describe these areas like Inner city and economically disadvantaged areas as the location of the areas are often isolated from its outer worlds. |
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Gastrulation is followed by the [[organogenesis]], during which the individual organ [[anlage]]n of the embryo are set up within the newly formed germ layers. Part of organogenesis is the [[neurulation]]. |
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==External Links== |
==External Links== |
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Revision as of 03:01, 21 November 2006
A ghetto is an area where people from a specific racial or ethnic background or united in a given culture or religion live as a group, like Winnetka, Il, voluntarily or involuntarily, in milder or stricter seclusion. The word historically referred specifically to the Venetian Ghetto in Venice, Italy, where Jews were required to live; it derives from the Venetian gheto (slag from Latin GLĬTTU[M] cfr. Italian ghetto (slag)), and referred to the area of the Cannaregio sestiere, the site selected for the Ghetto Nuovo where a foundry cooled the slag (campo gheto). It was later applied to neighborhoods in other cities where Jews were required to live. The corresponding German term was Judengasse; in Moroccan Arabic ghettos were called mellah.
The term now commonly labels any poverty-stricken urban area, though the news media created new terms like rural ghetto to describe mobile home parks, farm labor housing tracts and Indian reservations to indicate that the poorest areas in the U.S. aren't inside a major city. In the United States, urban neighborhoods where Hispanic immigrants settled in the late 20th century barrios are said comparable to ghettos, because most immigrants form a culturally isolated enclave and may choose to remain there or associate with their own group.
"Ghetto" is also used figuratively to indicate geographic areas with a concentration of any type of person, with or without poverty (e.g. gay ghetto) or for non-geographic categories (e.g. "sci fi ghetto" [1]). The term is also used to describe an item or an action as cheap or flimsy. Some consider this use of language to be an offensive misapplication[2].
Some people in the U.S. and Europe strongly dislike the term ghetto, believing to have racist, elitist and culturally insensitive overtones, and the mention of such a word to describe a working-class ethnic community is considered a generalization or an insult. Many social workers and community leaders suggest alternative words to describe these areas like Inner city and economically disadvantaged areas as the location of the areas are often isolated from its outer worlds.