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organogenesis

organogenesis The formation of organs during embryonic development. In animals this begins following the rearrangement of the cells at gastrulation, when the three germ layers are fully formed in their correct positions. Dividing cells of the gastrula begin to differentiate and the rudimentary organs and organ systems begin to form. See differentiation; ectoderm; endoderm; mesoderm.

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organogenesis

organogenesis A stage of embryogenesis in vertebrate embryos that follows the differentiation of the mesoderm and in which the development of organs occurs. Organs are derived from five basic types of tissues: epithelilial, connective, blood, muscular, and nervous. See also BLASTULA; GASTRULA; PHARANGULA.

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Organogenesis

Organogenesis

Organogensis refers to that period of time during development when the organs are being formed. After an egg has been fertilized, and has been implanted in the uterus, the developing form is known as the embryo. Organogenesis takes place during this embryonic phase. In fact, most organogenesis has begun as early as week five in humans (remember that a normal human pregnancy lasts an average of 40 weeks). Therefore, damage to any of the organ systems of the body which may ultimately result in some type of birth defect usually strikes during this time frame.

By week five, the buds of tissue which will become the limbs are in place. The structures which will become the skeleton, nervous system, and circulatory system of the face, neck, and jaws are in place. A five-week-old embryo has the early developmental structures of the esophagus, stomach, intestine, liver, and pancreas. The heart is already functioning, and continues to develop and change over this period of time. The respiratory system begins developing, as do blood vessels, blood cells, nervous and endocrine organs. Clearly, the most crucial organs of the human form are developing during organogenesis. Essentially, the earlier the injury to these developing buds of tissue, the more severe the ultimate defect. This is because these tiny buds of tissue hold all the primitive cells which should differentiate into the myriad number of cells necessary to create all of the varied organs of the human body.

It is an irony that, during this crucial period of development, when toxins from the outside world can have such devastating effects on the ultimate development of the embryo, many women are not even yet aware that they are pregnant, and are therefore not in the mindframe of protecting the developing embryo from exposure to such harmful substances as cigarette smoke, alcohol, certain drugs or medications, or extremes of heat (as could be experienced in a very hot Jacuzzi).

One of the most infamous agents (teratogens) responsible for widespread deformities during the period of organogenesis is a drug called thalidomide. Thalidomide was administered to women (particularly in Europe in the 1950s) because it was thought to combat the nausea present in early pregnancy. Over time, however, it became evident that babies born of thalidomide-using mothers had very high rates of serious limb deformities. In particular, the long bones of the limbs were either absent or seriously deformed. Furthermore, many of these children had associated defects of the heart and intestine. Thalidomide was ultimately determined to be at fault, causing the most severe defects when given between weeks four and six of pregnancy: the period of organogenesis. Thalidomide was subsequently withdrawn from the market.

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Organogenesis

Organogenesis

Organogensis refers to that period of time during development when the organs are being formed. After an egg has been fertilized, and has been implanted in the uterus, the developing form is known as the embryo. Organogenesis takes place during this embryonic phase. In fact, most organogenesis has begun as early as week five in humans (remember that a normal human pregnancy lasts an average of 40 weeks). Therefore, damage to any of the organ systems of the body which may ultimately result in some type of birth defect usually strikes during this time frame.

By week five, the buds of tissue which will become the limbs are in place. The structures which will become the skeleton, nervous system , and circulatory system of the face, neck, and jaws are in place. A five-week-old embryo has the early developmental structures of the esophagus, stomach, intestine, liver, and pancreas. The heart is already functioning, and continues to develop and change over this period of time. The respiratory system begins developing, as do blood vessels, blood cells, nervous and endocrine organs. Clearly, the most crucial organs of the human form are developing during organogenesis. Essentially, the earlier the injury to these developing buds of tissue, the more severe the ultimate defect. This is because these tiny buds of tissue hold all the primitive cells which should differentiate into the myriad number of cells necessary to create all of the varied organs of the human body.

It is an irony that, during this crucial period of development, when toxins from the outside world can have such devastating effects on the ultimate development of the embryo, many women are not even yet aware that they are pregnant, and are therefore not in the mindframe of protecting the developing embryo from exposure to such harmful substances as cigarette smoke , alcohol , certain drugs or medications, or extremes of heat (as could be experienced in a very hot Jacuzzi).

One of the most infamous agents (teratogens) responsible for widespread deformities during the period of organogenesis is a drug called thalidomide . Thalidomide was administered to women (particularly in Europe in the 1950s) because it was thought to combat the nausea present in early pregnancy. Over time, however, it became evident that babies born of thalidomide-using mothers had very high rates of serious limb deformities. In particular, the long bones of the limbs were either absent or seriously deformed. Furthermore, many of these children had associated defects of the heart and intestine. Thalidomide was ultimately determined to be at fault, causing the most severe defects when given between weeks four and six of pregnancy: the period of organo-genesis. Thalidomide was subsequently withdrawn from the market.

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"Organogenesis." The Gale Encyclopedia of Science. . Encyclopedia.com. 14 Nov. 2018 <https://www.encyclopedia.com>.

"Organogenesis." The Gale Encyclopedia of Science. . Encyclopedia.com. (November 14, 2018). https://www.encyclopedia.com/science/encyclopedias-almanacs-transcripts-and-maps/organogenesis

"Organogenesis." The Gale Encyclopedia of Science. . Retrieved November 14, 2018 from Encyclopedia.com: https://www.encyclopedia.com/science/encyclopedias-almanacs-transcripts-and-maps/organogenesis

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Because each style has its own formatting nuances that evolve over time and not all information is available for every reference entry or article, Encyclopedia.com cannot guarantee each citation it generates. Therefore, it’s best to use Encyclopedia.com citations as a starting point before checking the style against your school or publication’s requirements and the most-recent information available at these sites:

Modern Language Association

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American Psychological Association

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Notes:
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  • In addition to the MLA, Chicago, and APA styles, your school, university, publication, or institution may have its own requirements for citations. Therefore, be sure to refer to those guidelines when editing your bibliography or works cited list.