発生学

関: embryol、embryological

WordNet

the branch of biology that studies the formation and early development of living organisms

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胎生学,発生学

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出典(authority):フリー百科事典『ウィキペディア（Wikipedia）』「2014/07/10 22:36:31」(JST)

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1 - morula, 2 - blastula

1 - blastula, 2 - gastrula with blastopore; orange - ectoderm, red - endoderm.

Dissection of human embryo, 38 mm - 8 weeks

Embryology (from Greek ἔμβρυον, embryon, "the unborn, embryo"; and -λογία, -logia) is the science of the development of an embryo from the fertilization of the ovum to the fetus stage.

Embryonic development of animals

After cleavage, the dividing cells, or morula, becomes a hollow ball, or blastula, which develops a hole or pore at one end.

Bilaterals

In bilateral animals, the blastula develops in one of two ways that divides the whole animal kingdom into two halves (see: Embryological origins of the mouth and anus). If in the blastula the first pore (blastopore) becomes the mouth of the animal, it is a protostome; if the first pore becomes the anus then it is a deuterostome. The protostomes include most invertebrate animals, such as insects, worms and molluscs, while the deuterostomes include the vertebrates. In due course, the blastula changes into a more differentiated structure called the gastrula.

The gastrula with its blastopore soon develops three distinct layers of cells (the germ layers) from which all the bodily organs and tissues then develop:

The innermost layer, or endoderm, gives a rise to the digestive organs, the gills, lungs or swim bladder if present, and kidneys or nephrites.
The middle layer, or mesoderm, gives rise to the muscles, skeleton if any, and blood system.
The outer layer of cells, or ectoderm, gives rise to the nervous system, including the brain, and skin or carapace and hair, bristles, or scales.

Embryos in many species often appear similar to one another in early developmental stages. The reason for this similarity is because species have a shared evolutionary history. These similarities among species are called homologous structures, which are structures that have the same or similar function and mechanism, having evolved from a common ancestor.

Humans

Humans are bilaterals and deuterostomes.

In humans, the term embryo refers to the ball of dividing cells from the moment the zygote implants itself in the uterus wall until the end of the eighth week after conception. Beyond the eighth week after conception (tenth week of pregnancy), the developing human is then called a fetus.

History of embryology

Human embryo at six weeks gestational age

Histological film 10 day mouse embryo

Beetle larvae

As recently as the 18th century, the prevailing notion in human embryology was preformation: the idea that semen contains an embryo — a preformed, miniature infant, or "homunculus" — that simply becomes larger during development. The competing explanation of embryonic development was epigenesis, originally proposed 2,000 years earlier by Aristotle. Much early embryology came from the work of the great Italian anatomists: Aldrovandi, Aranzio, Leonardo da Vinci, Marcello Malpighi, Gabriele Falloppio, Girolamo Cardano, Emilio Parisano, Fortunio Liceti, Stefano Lorenzini, Spallanzani, Enrico Sertoli, Mauro Rusconi, etc.^[1] According to epigenesis, the form of an animal emerges gradually from a relatively formless egg. As microscopy improved during the 19th century, biologists could see that embryos took shape in a series of progressive steps, and epigenesis displaced preformation as the favoured explanation among embryologists.^[2]

After 1827

8-9 weeks human embryo

Karl Ernst von Baer and Heinz Christian Pander proposed the germ layer theory of development; von Baer discovered the mammalian ovum in 1827.^[3]^[4]^[5] Modern embryological pioneers include Charles Darwin, Ernst Haeckel, J.B.S. Haldane, and Joseph Needham. Other important contributors include William Harvey, Kaspar Friedrich Wolff, Heinz Christian Pander, August Weismann, Gavin de Beer, Ernest Everett Just, and Edward B. Lewis.

After 1950

After the 1950s, with the DNA helical structure being unravelled and the increasing knowledge in the field of molecular biology, developmental biology emerged as a field of study which attempts to correlate the genes with morphological change, and so tries to determine which genes are responsible for each morphological change that takes place in an embryo, and how these genes are regulated.

Vertebrate and invertebrate embryology

Many principles of embryology apply to invertebrates as well as to vertebrates.^[6] Therefore, the study of invertebrate embryology has advanced the study of vertebrate embryology. However, there are many differences as well. For example, numerous invertebrate species release a larva before development is complete; at the end of the larval period, an animal for the first time comes to resemble an adult similar to its parent or parents. Although invertebrate embryology is similar in some ways for different invertebrate animals, there are also countless variations. For instance, while spiders proceed directly from egg to adult form, many insects develop through at least one larval stage.

Modern embryology research

Currently, embryology has become an important research area for studying the genetic control of the development process (e.g. morphogens), its link to cell signalling, its importance for the study of certain diseases and mutations and in links to stem cell research.

References

^ Massimo De Felici, Gregorio Siracus, The rise of embryology in Italy: from the Renaissance to the early 20th Century, Int. J. Dev. Biol. 44: 515-521 (2000).
^ Campbell et al. (p. 987)
^ K. J. Betteridge (1981). "An historical look at embryo transfer". Reproduction. the Journal of the Society for Reproduction and Fertility 62 (1): 1–13. doi:10.1530/jrf.0.0620001. "Three years later, the Estonian, Karl Ernst von Baer, finally found the true mammalian egg in a pet dog (von Baer, 1827)."
^ Lois N. Magner (2005). History of the Life Sciences. New York. Basel: Marcel Dekker. p. 166. ISBN 9780824743604.
^ Alex Lopata (2009). "History of the Egg in Embryology". Journal of Mammalian Ova Research 26: 2–9. doi:10.1274/jmor.26.2.
^ Parker, Sybil. "Invertebrate Embryology," McGraw-Hill Encyclopedia of Science & Technology (McGraw-Hill 1997).

Embryology - History of embryology as a science." Science Encyclopedia. Web. 06 Nov. 2009. <http://science.jrank.org/pages/2452/Embryology.html>.
"Germ layer." Encyclopædia Britannica. 2009. Encyclopædia Britannica Online. 06 Nov. 2009 <http://www.britannica.com/EBchecked/topic/230597/germ-layer>.

External links

Wikimedia Commons has media related to Embryology.

Online course in embryology
Indiana University's Human Embryology Animations
UNSW Embryology Large resource of information and media.
What is a human admixed embryo?
Definition of embryo according to Webster
Embryonews _ resource for IVF and embryology articles

UpToDate Contents

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English Journal

c-Flip KO fibroblasts display lipid accumulation associated with endoplasmic reticulum stress.

Giampietri C1, Petrungaro S2, Conti S2, Facchiano A3, Filippini A2, Ziparo E2.
Biochimica et biophysica acta.Biochim Biophys Acta.2015 Jul;1851(7):929-36. doi: 10.1016/j.bbalip.2015.02.018. Epub 2015 Mar 5.
c-Flip proteins are well-known apoptosis modulators. They generally contribute to tissue homeostasis maintenance by inhibiting death-receptor-mediated cell death. In the present manuscript, we show that c-Flip knock-out (KO) mouse embryonic fibroblasts (MEFs) kept in culture under starvation conditi
PMID 25746012
PMID 25845979

Grafted murine induced pluripotent stem cells prevent death of injured rat motoneurons otherwise destined to die.

Pajer K1, Nemes C2, Berzsenyi S2, Kovács KA2, Pirity MK2, Pajenda G3, Nógrádi A4, Dinnyés A5.
Experimental neurology.Exp Neurol.2015 Jul;269:188-201. doi: 10.1016/j.expneurol.2015.03.031. Epub 2015 Apr 16.
Human plexus injuries often include the avulsion of one or more ventral roots, resulting in debilitating conditions. In this study the effects of undifferentiated murine iPSCs on damaged motoneurons were investigated following avulsion of the lumbar 4 (L4) ventral root, an injury known to induce the
PMID 25889458

Japanese Journal

ガードン卿のノーベル賞受賞研究 : そのクローンガエル、分子発生学、およびライフスタイルの魅力

塩川光一郎
帝京大学宇都宮キャンパス研究年報. 人文編 (19), 1-55, 2013-12
NAID 40019944987

生物器官の形跡を残した中国産ジュラ紀初期の恐竜の胚子発生を示す化石(地球科学の窓)

高橋正志
地球科學 67(4), 155, 2013-07-25
NAID 110009624761

分類学に基づいた動物学 : 海綿動物を例に, "海綿動物門第4の綱: 同骨海綿綱"(2012年度日本動物分類学会シンポジウム)

伊勢優史
タクサ : 日本動物分類学会誌 (34), 18-24, 2013-02-28
… Morphology, embryology and developmental property of homoscleromorph sponges are distinct from those of Demospongiae, rather similar to those of eumetazoans in possession of basement membrane. …
NAID 110009595003

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リンク元	「発生学」「embryological」「embryol」

「発生学」

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英: embryology

１．頭頚部の神経堤細胞の分化

２．鰓弓の神経要素、筋要素、骨格要素を表にしてまとめる

　　　　　神経　　　　　　　筋　　　　　骨格
第一鰓弓　三叉神経(CN V  )　咀嚼筋　　　上顎骨、下顎骨、キヌタ骨、ツチ骨
第二鰓弓　顔面神経(CN VII)　顔面表情筋　アブミ骨、茎状突起、茎状舌骨靱帯、舌骨小角と舌骨体の上部
第三鰓弓　舌咽神経(CN IX )　茎突咽頭筋　舌骨大角と舌骨体の下部
第四鰓弓　迷走神経(CN X  )　喉頭内の筋　喉頭軟骨

３．咽頭嚢由来の構造

４．舌の形成と神経支配~

　発生第四週に第一鰓弓の間葉から二つの外側舌隆起と一つの無対舌結節が出現し、これらが舌体を形成する。そして、結合節は第二，三鰓弓と第四鰓弓の一部の間葉から形成され、これが舌根を形成する。これらの神経支配は以下の通りである。

　　　　　　　　　舌体　　　　　　　｜［有郭乳頭］　　舌根
　　　　　　　　　前2/3 　　　　　　｜　▼［分界稜］　後1/3
　　　　　　　　　　　　　　　　　　｜　　　▼
感覚神経（特殊）　顔面神経（CN VII）｜　　　　　　　　舌咽神経（CN IX ）、最後方は迷走神経(CN X)
感覚神経（一般）　三叉神経（CN V  ）｜　　　　　　　　舌咽神経（CN IX ）、最後方は迷走神経(CN X)
運動神経　　　　　舌下神経（CN XII）｜　　　　　　　　舌下神経（CN XII）
発生学的起源　　　第一鰓弓　　　　　　　　　　　　　　第二・三・鰓弓＋四鰓弓の一部

５．顔面・口蓋・鼻腔の形成過程~

　発生第四週に、顔面を形成する三つの隆起である、上顎隆起、下顎隆起、および前頭鼻隆起とが出現する。発生第五週には、鼻窩を取り巻く組織が隆起して、鼻隆起を形成する。鼻隆起の内側が内側鼻隆起であり、鼻隆起の外側が外側鼻隆起となる。発生第六週から第十四週にかけて、上顎隆起が内側に向かって成長する結果、内側鼻隆起と上顎鼻隆起が癒合して上唇を形成する。また、両側の内側鼻隆起が正中で癒合して顎間部と人中を形成する。

６．視覚器の形成と誘導因子の働き~

　視覚器は前脳両側における一対の膨出として発生し始め、発生第四週末に眼胞となる。表層外胚葉の下層に達し、表層外胚葉を誘導して、水晶体板に分化させる。その後、眼胞は陥入し、眼杯を形成する。水晶体板も陥入して水晶体胞となる。眼杯からは網膜が、水晶体胞からは水晶体が形成される。~ 　前脳で眼形成を誘導するのは、PAX6である。眼形成領域は、神経管形成前には頭方の神経ヒダに単一の帯をなして存在している。この領域にPAX6が発現している。脊索前板で発現するShhが眼形成の中央部分に作用し、PAX2の発現を誘導する。PAX2はPAX6の発現を抑制し、この発現パターンは眼形成が始まるまで維持される。このため、PAX2、PAX6を発現する領域はそれぞれ眼茎、眼杯に分化する。

７．聴覚器（内耳・中耳・外耳・耳介）の形成過程）~

　内耳は菱脳の両側にある表層外胚葉が肥厚した耳板から形成される。耳板は陥入して耳窩となり、そして嚢状の耳胞を形成する。耳胞の腹側要素からは蝸牛管と球形嚢が、背側要素からは半規管、卵形嚢、内リンパ管が形成される。~ 　中耳は鼓室、耳管、小耳骨、および筋肉、神経より構成される。第一咽頭嚢は発生の過程で急激に側方に拡張して第一鰓溝に接する。第一咽頭嚢の遠位端が鼓室となり、狭窄したままの近位端が耳管となる。小耳骨のうち、ツチ骨とキヌタ骨は第一鰓弓の軟骨に由来し、アブミ骨は第二鰓弓に由来する。~ 　外耳は第一鰓溝に由来し、鼓膜により鼓室から隔てられている。鼓膜は外胚葉性上皮被覆、中間の間葉層、第一咽頭嚢からの内胚葉性被覆で覆われている。~ 　耳介は第一、第二鰓弓に並んでいる6個の間葉性小丘から発生する。