WordNet

prepare or position for action or operation; "lay a fire"; "lay the foundation for a new health care plan"
put in a horizontal position; "lay the books on the table"; "lay the patient carefully onto the bed" (同)put down, repose
impose as a duty, burden, or punishment; "lay a responsibility on someone"
lay eggs; "This hen doesnt lay"
not of or from a profession; "a lay opinion as to the cause of the disease"
make or form a layer; "layer the different colored sands"
single thickness of usually some homogeneous substance; "slices of hard-boiled egg on a bed of spinach" (同)bed
a hen that lays eggs
thin structure composed of a single thickness of cells
a relatively thin sheetlike expanse or region lying over or under another
a small apparently simple structure (as a fertilized egg) from which new tissue can develop into a complete organism
with one layer on top of another; "superimposed rocks" (同)superimposed

PrepTutorEJDIC

《場所の副詞[句]を伴って》‘を'『置く』,横たえる / ‘を'『きちんと置く』(並べる),〈土台など〉‘を'すえる,〈鉄道など〉‘を'敷設する / …‘を'『用意する』,準備する / (…に)〈身体の一部〉‘を'置く,つける《+『名』+『on』(『to』)+『名』》 / (…に)〈信頼・愛情〉‘を'置く,寄せる,託す;〈強調・重要性など〉‘を'置く《+『名』+『on』+『名』》 / 〈ほこり・波・風など〉‘を'押さえる,〈恐れ亡霊など〉‘を'静める,なだめる / 〈卵〉‘を'産む / 〈かけ〉‘を'する;(…に)〈金〉‘を'かける《+『名』+『on』+『名』》 / (…に)〈税・罰金・義務など〉‘を'課する,〈重荷・責任など〉‘を'負わせる《+『名』+『on』(『upon』)+『名』》 / 〈悪事など〉‘を'(…の)せいにする《+『名』+『against』(『to』)+『名』》 / 《状態を表す副詩[句]を伴って》(特によくない状態に)…‘を'『置く』,する / (…に)〈権利の主張・報告など〉‘を'提出する,申し出る《+『名』+『before』(『to』)+『名』》 / (…で)…‘の'表面をおおう《+『名』+『with』+『名』》;(…に)…‘を'広げる《+『名』+『on』+『名』》 / 卵を産む / 位置,配置,地形,地勢
lieの過去形
(歌うために書かれた)短い物語詩 / 《詩》(一般に)歌,調べ
(僧職にある人に対して)俗人の / (専門家に対して)しろうとの,門外漢の
《複合語を作って》(物を)積む人(物),置く人(物) / 卵を産む鶏・層;(ペンキなどの)一塗り;一皮 / (園芸で)取り木 / …‘を'層にする / 〈植物〉‘を'取り木する
細菌,ばい菌 / (植物の)胚(はい),幼芽;(動物の)卵子 / 原因;(発達の)初期

Wikipedia preview

出典(authority):フリー百科事典『ウィキペディア（Wikipedia）』「2013/05/14 21:55:13」(JST)

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A germ layer, occasionally referred to as a germinal epithelium, is a group of cells, formed during animal embryogenesis.^[1] Germ layers are particularly pronounced in the vertebrates; however, all animals more complex than sponges (eumetazoans and agnotozoans) produce two or three primary tissue layers (sometimes called primary germ layers). Animals with radial symmetry, like cnidarians, produce two germ layers (the ectoderm and endoderm) making them diploblastic. Animals with bilateral symmetry produce a third layer between these two layers (appropriately called the mesoderm) making them triploblastic. Germ layers eventually give rise to all of an animal’s tissues and organs through the process of organogenesis.

Germ layers [edit]

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).

Micrograph of a teratoma, a tumour that characteristically has tissue from all three germ layers. The image shows tissue derived from the mesoderm (immature cartilage - left-upper corner of image), endoderm (gastrointestinal glands - center-bottom of image) and ectoderm (epidermis - right of image). H&E stain.

Caspar Friedrich Wolff observed organization of the early embryo in leaf-like layers. In 1817, Heinz Christian Pander discovered three primordial germ layers while studying chick embryos. Between 1850 and 1855, Robert Remak had further refined the germ cell layer concept, and introduced into English were the terms "mesoderm" by Huxley in 1871 and "ectoderm" and "endoderm" by Lankester in 1873.

Among animals, sponges show the simplest organization, having a single germ layer. Although they have differentiated cells (e.g. collar cells), they lack true tissue coordination. Diploblastic animals, Cnidaria and Ctenophora, show an increase in complexity, having two germ layers, the endoderm and ectoderm. Diploblastic animals are organized into recognisable tissues. All higher animals (from flatworms to humans) are triploblastic, possessing a mesoderm in addition to the germ layers found in Diploblasts. Triploblastic animals develop recognisable organs.

Development [edit]

Fertilization leads to the formation of a zygote. During the next stage, cleavage, mitotic cell divisions transform the zygote into a tiny ball of cells, a blastula. This early embryonic form undergoes gastrulation, forming a gastrula with either two or three layers (the germ layers). In all vertebrates, these are the forerunners of all adult tissues and organs.^[2]

In humans, after about three days, the zygote forms a solid mass of cells by mitotic division, called a morula. This then changes to a blastocyst, consisting of an outer layer called a trophoblast, and an inner cell mass called the embryoblast. Filled with uterine fluid, the blastocyst breaks out of the zona pellucida and undergoes implantation. The inner cell mass initially has two layers: the hypoblast and epiblast. At the end of the second week, a primitive streak appears. The epiblast in this region moves towards the primitive streak, dives down into it, and forms a new layer, called the endoderm, pushing the hypoblast out of the way (this goes on to form the amnion.) The epiblast keeps moving and forms a second layer, the mesoderm. The top layer is now called the ectoderm.^[3]

Endoderm [edit]

The endoderm produces tissue within the lungs, thyroid, and pancreas.

Main article: Endoderm

The endoderm is one of the germ layers formed during animal embryogenesis. Cells migrating inward along the archenteron form the inner layer of the gastrula, which develops into the endoderm.

The endoderm consists at first of flattened cells, which subsequently become columnar. It forms the epithelial lining of the whole of the digestive tube except part of the mouth and pharynx and the terminal part of the rectum (which are lined by involutions of the ectoderm). It also forms the lining cells of all the glands which open into the digestive tube, including those of the liver and pancreas; the epithelium of the auditory tube and tympanic cavity; the trachea, bronchi, and air cells of the lungs; the urinary bladder and part of the urethra; and the follicle lining of the thyroid gland and thymus.

The endoderm forms: the stomach, the colon, the liver, the pancreas, the urinary bladder, the epithelial parts of trachea, the lungs, the pharynx, the thyroid, the parathyroid, and the intestines^{[citation needed]}.

Mesoderm [edit]

The mesoderm aids in the production of cardiac muscle, skeletal muscle, smooth muscle, tissues within the kidneys, and red blood cells.

Main article: Mesoderm

The mesoderm germ layer forms in the embryos of triploblastic animals. During gastrulation, some of the cells migrating inward contribute to the mesoderm, an additional layer between the endoderm and the ectoderm^{[citation needed]}. The formation of a mesoderm led to the development of a coelom. Organs formed inside a coelom can freely move, grow, and develop independently of the body wall while fluid cushions and protects them from shocks^{[citation needed]}.

The mesoderm has several components which develop into tissues: intermediate mesoderm, paraxial mesoderm, lateral plate mesoderm, and chorda-mesoderm. The chorda-mesoderm develops into the notochord. The intermediate mesoderm develops into kidneys and gonads. The paraxial mesoderm develops into cartilage, skeletal muscle, and dermis. The lateral plate mesoderm develops into the circulatory system (including the heart and spleen), the wall of the gut, and wall of the human body .^[4]

Through cell signaling cascades and interactions with the ectodermal and endodermal cells, the mesodermal cells begin the process of differentiation.^[5]

Ectoderm [edit]

The ectoderm produces tissues within the epidermis, aids in the formation of neurons within the brain, and constructs melanocytes.

Main article: Ectoderm

The ectoderm generates the outer layer of the embryo, and it forms from the embryo's epiblast.^[6] The ectoderm develops into the surface ectoderm, neural crest, and the neural tube.^[7]

The surface ectoderm develops into: epidermis, hair, nails, lens of the eye, sebaceous glands, cornea, tooth enamel, the epithelium of the mouth and nose.

The neural crest of the ectoderm develops into: peripheral nervous system, adrenal medulla, melanocytes, facial cartilage, dentin of teeth.

The neural tube of the ectoderm develops into: brain, spinal cord, posterior pituitary, motor neurons, retina.

Note: The anterior pituitary develops from the ectodermal tissue of Rathke's pouch.

Neural crest [edit]

Because of its great importance, the neural crest is sometimes considered a fourth germ layer.^[8] It is, however, derived from the ectoderm.

References [edit]

^ Gilbert, Scott F (2003). "The Epidermis and the Origin of Cutaneous Structures". Developmental Biology. Sinauer Associates.
^ Gilbert, Scott F (2000). "Comparative Embryology". Developmental Biology. Sinauer Associates.
^ Gilbert, Scott F (2000). "Early Mammalian Development". Developmental Biology. Sinauer Associates.
^ Gilbert, Scott F (2003). "Paraxial and Intermediate Mesoderm". Developmental Biology. Sinauer Associates.
^ Brand, Thomas (1 June 2003). "Heart development: molecular insights into cardiac specification and early morphogenesis". Developmental Biology 258 (1): 1–19. doi:10.1016/S0012-1606(03)00112-X.
^ Gilbert, Scott F (2003). "Early Mammalian Development". Developmental Biology. Sinauer Associates.
^ Gilbert, Scott F (2003). "The Central Nervous System and The Epidermis". Developmental Biology. Sinauer Associates.
^ Hall BK (2000) The neural crest as a fourth germ layer and vertebrates as quadroblastic not triploblastic. Evolution & Development 2, 3-5 pmid=11256415 url=http://onlinelibrary.wiley.com/resolve/openurl?genre=article&sid=nlm:pubmed&issn=1520-541X&date=2000&volume=2&issue=1&spage=3

UpToDate Contents

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English Journal

Generation of induced pluripotent stem cells without genetic defects by small molecules.

Park HS1, Hwang I1, Choi KA1, Jeong H1, Lee JY2, Hong S3.
Biomaterials.Biomaterials.2015 Jan;39:47-58. doi: 10.1016/j.biomaterials.2014.10.055. Epub 2014 Nov 15.
The generation of induced pluripotent stem cells (iPSCs) often causes genetic and epigenetic defects, which may limit their clinical applications. Here, we show that reprogramming in the presence of small molecules preserved the genomic stability of iPSCs by inhibiting DNA double-strand breaks (DSBs
PMID 25477171

Pericytes at the intersection between tissue regeneration and pathology.

Birbrair A, Zhang T1, Wang ZM1, Messi ML1, Mintz A2, Delbono O.
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Perivascular multipotent cells, pericytes, contribute to the generation and repair of various tissues in response to injury. They are heterogeneous in their morphology, distribution, origin and markers, and elucidating their molecular and cellular differences may inform novel treatments for disorder
PMID 25236972

On human development: lessons from stem cell systems.

Medvinsky A1, Livesey FJ2.
Development (Cambridge, England).Development.2015 Jan 1;142(1):17-20.
In September 2014, over 100 scientists from around the globe gathered at Wotton House near London for the Company of Biologists' workshop 'From Stem Cells to Human Development'. The workshop covered diverse aspects of human development, from the earliest stages of embryogenesis to differentiation of
PMID 25516966

Japanese Journal

Sub-Bandgap External Quantum Efficiency in Ti Implanted Si Heterojunction with Intrinsic Thin Layer Cells

Silvestre Santiago,Boronat Alfredo,Colina Mónica,Castañer Luis,Olea Javier,Pastor David,Prado Alvaro del,Mártil Ignacio,González-Díaz Germán,Luque Antonio,Antolín Elisa,Hernández Estela,Ramiro Iñigo,Artacho Irene,López Esther,Martí Antonio
Jpn J Appl Phys 52(12), 122302-122302-5, 2013-12-25
… In this work we present the manufacturing processes and results obtained from the characterization of heterojunction with intrinsic thin layer solar cells that include a heavily Ti ion implanted Si absorbing layer. … We discuss the origin of this below-bandgap photocurrent and the modifications in the hydrogenated amorphous intrinsic Si layer thickness to increase the open-circuit voltage. …
NAID 150000107837