関: umbilical vesicle

WordNet

nutritive material of an ovum stored for the nutrition of an embryo (especially the yellow mass of a bird or reptile egg) (同)vitellus
a structure resembling a bag in an animal

PrepTutorEJDIC

(卵の)黄身,卵黄
小袋,のう(動植物の内部にあり,特に液を含んだもの)

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出典(authority):フリー百科事典『ウィキペディア（Wikipedia）』「2014/09/29 05:02:51」(JST)

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The 'yolk sac' is a membranous sac attached to an embryo, providing early nourishment in the form of yolk in bony fishes, sharks, reptiles, birds, and mammals. It functions as the developmental circulatory system of the human embryo, before internal circulation begins.

In humans

Contents in the cavity of the uterus seen at approximately 5 weeks of gestational age by obstetric ultrasonography.

Artificially colored, showing gestational sac, yolk sac and embryo (measuring 3 mm as the distance between the + signs).

It is the first element seen in the gestational sac during pregnancy, usually at 3 days gestation. It is a critical landmark, identifying a true gestation sac. It is reliably seen early in human pregnancy using ultrasound.

The yolk sac is situated on the ventral aspect of the embryo; it is lined by extra-embryonic endoderm, outside of which is a layer of extra-embryonic mesenchyme, derived from the mesoderm.

Blood is conveyed to the wall of the sac by the primitive aorta, and after circulating through a wide-meshed capillary plexus, is returned by the vitelline veins to the tubular heart of the embryo. This constitutes the vitelline circulation, and by means of it nutritive material is absorbed from the yolk sac and conveyed to the embryo.

At the end of the fourth week the yolk sac presents the appearance of a small pear-shaped vesicle (umbilical vesicle) opening into the digestive tube by a long narrow tube, the vitelline duct.

The vesicle can be seen in the afterbirth as a small, somewhat oval-shaped body whose diameter varies from 1 mm. to 5 mm.; it is situated between the amnion and the chorion and may lie on or at a varying distance from the placenta.

As a rule the duct undergoes complete obliteration during the seventh week, but in about two percent of cases its proximal part persists as a diverticulum from the small intestine, Meckel's diverticulum, which is situated about 60 cm proximal to the ileocecal valve, and may be attached by a fibrous cord to the abdominal wall at the umbilicus.

Sometimes a narrowing of the lumen of the ileum is seen opposite the site of attachment of the duct.

In fish

All bony fishes, some sharks and rays have yolk sacs at some stage of development, with all oviparous fishes retaining the sac after hatching. Lamniform sharks are ovoviviparous, in that their eggs hatch in utero, in addition to eating unfertilized eggs, unborn sharks participate in intrauterine-cannibalism: stronger pups consume their weaker womb-mates.^[1]^[2]^[3]

Histogenesis

The yolk sac starts forming itself during the second week of the embryonic development, at the same time of the shaping of the amniotic sac. The hypoblast starts proliferating laterally and descending.

In the meantime Heuser's membrane, located on the opposite pole of the developing vesicle, starts its upward proliferation and meets the hypoblast.

Modifications

Primary yolk sac/primitive yolk sac: it is the vesicle constituted in the second week, its floor is represented by Heuser's membrane and its ceiling by the epiblast. It is also known as the exocoelomic cavity.^[4]

Secondary yolk sac: this first transformation is determined by the modification of its cover, in the connection zone between the hypoblast and the Heuser membrane. We can observe a structure. The two parts detach and the inferior one, which is smaller, forms a cyst destined to be eliminated. The upper one is now covered only by the hypoblast.

The final yolk sac: during the fourth week of development, during which we can see the shaping of the embryonic areas. A little portion of the sac, in the upper part, constitutes the intestinal tube. On the other side, the distal part forms a little vesicle that is what remains of the yolk sac.

Additional images

Surface view of embryo of Hylobates concolor.
Human embryo—length, 2 mm. Dorsal view, with the amnion laid open. X 30.
Dorsum of human embryo, 2.11 mm. in length.
Section through the embryo.
Diagram showing earliest observed stage of human ovum.
Diagram illustrating early formation of allantois and differentiation of body-stalk.
Diagram showing later stage of allantoic development with commencing constriction of the yolk-sac.
Diagram illustrating a later stage in the development of the umbilical cord.
Fetus of about eight weeks, enclosed in the amnion. Magnified a little over two diameters.
Model of human embryo 1.3 mm. long.
Section through ovum imbedded in the uterine decidua
Human embryo about fifteen days old. Brain and heart represented from right side. Digestive tube and yolk sac in median section.

References

^ Meisner, A & Burns, J: Viviparity in the Halfbeak Genera Dermogenys and Nomorhamphus (Teleostei: Hemiramphidae). Journal of Morphology 234, pp. 295–317, 1997
^ Peter Scott: Livebearing Fishes, p. 13. Tetra Press 1997. ISBN 1-56465-193-2
^ Leonard J. V. Compagno (1984). Sharks of the World: An annotated and illustrated catalogue of shark species known to date. Food and Agriculture Organization of the United Nations. ISBN 92-5-104543-7. OCLC 156157504.
^ "Text for first three lectures". Retrieved 2007-10-13.

UpToDate Contents

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1. 妊娠期間および出産予定日の出生前評価 prenatal assessment of gestational age and estimated date of delivery
2. 部位不明妊娠の超音波検査 ultrasonography of pregnancy of unknown location
3. 妊娠早期の臨床症状および診断 clinical manifestations and diagnosis of early pregnancy
4. 卵巣胚細胞腫瘍：病理学、臨床症状、および診断 ovarian germ cell tumors pathology clinical manifestations and diagnosis
5. 一絨毛膜性双胎妊娠 monoamniotic twin pregnancy

English Journal

Maternal nutrition modifies trophoblast giant cell phenotype and fetal growth in mice.

Watkins AJ1, Lucas ES2, Marfy-Smith S2, Bates N2, Kimber SJ2, Fleming TP2.
Reproduction (Cambridge, England).Reproduction.2015 Jun;149(6):563-75. doi: 10.1530/REP-14-0667. Epub 2015 Mar 9.
Mammalian placentation is dependent upon the action of trophoblast cells at the time of implantation. Appropriate fetal growth, regulated by maternal nutrition and nutrient transport across the placenta, is a critical factor for adult offspring long-term health. We have demonstrated that a mouse mat
PMID 25755287

Preparation, cytotoxicity and in vivo bioimaging of highly luminescent water-soluble silicon quantum dots.

Fan JW1, Vankayala R, Chang CL, Chang CH, Chiang CS, Hwang KC.
Nanotechnology.Nanotechnology.2015 May 29;26(21):215703. doi: 10.1088/0957-4484/26/21/215703. Epub 2015 May 6.
Designing various inorganic nanomaterials that are cost effective, water soluble, optically photostable, highly fluorescent and biocompatible for bioimaging applications is a challenging task. Similar to semiconducting quantum dots (QDs), silicon QDs are another alternative and are highly fluorescen
PMID 25943071

Short-term exposure to low doses of rotenone induces developmental, biochemical, behavioral, and histological changes in fish.

Melo KM1, Oliveira R, Grisolia CK, Domingues I, Pieczarka JC, de Souza Filho J, Nagamachi CY.
Environmental science and pollution research international.Environ Sci Pollut Res Int.2015 May 7. [Epub ahead of print]
Rotenone, a natural compound derived from plants of the genera Derris and Lonchocarpus, is used worldwide as a pesticide and piscicide. This study aims to assess short-term toxicity of rotenone to early-life stages of the fish Danio rerio and Poecilia reticulata using a wide and integrative range of
PMID 25948382

Japanese Journal

対照的な手術術式を行ったyolk sac tumorの2症例

明野慶子,土井宏太郎,大塚晃生 [他]
産科と婦人科 82(3), 333-336, 2015-03
NAID 40020371382

Characterization of Avian Encephalomyelitis Outbreaks Occurred in South Korea from 2006 to 2013

, ,
The Journal of Poultry Science 52(2), 151-155, 2015
… In the embryo-inoculation test via the yolk sac, only one field strain and one commercial vaccine were embryo-adapted. …
NAID 130005066314

Erythropoietin Gene Expression: Developmental-Stage Specificity, Cell-Type Specificity, and Hypoxia Inducibility

The Tohoku Journal of Experimental Medicine 235(3), 233-240, 2015
… The first Epo-producing cells emerge in the neural crest and neuroepithelium of mid-stage embryos and support primitive erythropoiesis in the yolk sac. …
NAID 130004822447

Related Pictures

★リンクテーブル★

リンク元	「卵黄嚢」「umbilical vesicle」
拡張検索	「yolk sac endodermal」「yolk sac endoderm」
関連記事	「sac」「yolk」

「卵黄嚢」

Yolk sac
	Human embryo of 2.6 mm.
	Human embryo from thirty-one to thirty-four days
Latin	vesicula umbilicalis; saccus vitellinus
Gray's	p.54
Carnegie stage	5b
Days	9
Precursor	endoderm
Code	TE E5.7.1.0.0.0.4
MeSH	Yolk+Sac