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Topic: Allantois

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Developmental biology

Gastrulation

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Embryogenesis

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	Extraembryonic tissue: Allantois (Site not responding. Last check: 2007-10-24)
		As the caudal flexure develops and the yolk sac stalk moves cephalad, the cloacal membrane and the diverticulum become separated by a layer of mesoderm, the allantois being situated cephalad to the cloacal membrane.
		The cephalic portion of the future urogenital sinus (the mouth of the allantois) is known as the urachal region and the allantois slowly begins to solidify over the next few stages forming the urachus.
		The lumen of the allantois at it's junction with the urogenital sinus is obliterated by cells and the allantois forms the urachus or median umbilical ligament.
	www.ana.ed.ac.uk /anatomy/humat/notes/extraemb/allanto.htm (346 words)

	I. Embryology. 11. Development of the Fetal Membranes and Placenta. Gray, Henry. 1918. Anatomy of the Human Body. (Site not responding. Last check: 2007-10-24)
		The diverticulum is lined by entoderm and covered by mesoderm, and in the latter are carried the allantoic or umbilical vessels.
		If its further development be traced in the bird, it is seen to project to the right side of the embryo, and, gradually expanding, it spreads over its dorsal surface as a flattened sac between the amnion and the serosa, and extending in all directions, ultimately surrounds the yolk.
		The lateral leaves of somatopleure then grow round on each side, and, meeting on the ventral aspect of the allantois, enclose the vitelline duct and vessels, together with a part of the extra-embryonic celom; the latter is ultimately obliterated.
	www.bartleby.com /107/12.html (3196 words)

	Chickscope 1.5: Explore: Embryology: Day 4 - Setting Up Camp: Extra-embryonic Membranes
		The allantois is the embryo's connection to the chorion.
		The allantois grows larger as the chick grows, wraps around above the chick, and fuses with the chorion.
		When the chick hatches, the chorio- allantoic membrane remains attached to the egg shell and is therefore discarded with it.
	chickscope.beckman.uiuc.edu /explore/embryology/day04/4Focuson_1.html (424 words)

	Comparative Placentation
		Diplokaryocytes were again noted and the tall epithelium of the villus-free chorion was likened to the focal scars of horse placentas that are believed to overlie the uterine glands and may absorb "uterine milk".
		The reflected allantois, in turn, is fused with the chorionic membrane on whose outside reside the trophoblastic epithelium and villi.
		Amnion and allantois are densely adherent in the thin sac that encloses the fetus (Fig.
	medicine.ucsd.edu /cpa/rhino.html (4860 words)

	Patent 6,828,144
		During its early development, the murine allantois consists of an inner core of mesoderm and an outer layer of squamous epithelium referred to as a mesothelium.
		In the allantois, the transplanted cells appeared as various cell types, including endothelial cells which would be expected to line the vasculature of the umbilical cord.
		Once appropriate allantois cells have been produced, the cells will be injected into the exocelomic cavity of the defective embryo or transplanted directly onto a particular region of the fetus.
	www.pharmcast.com /Patents100/Yr2004/Dec2004/120704/6828144_Allantois120704.htm (4925 words)

	TheFetus.net - Completely patent urachus -William Meyer, MD, Daniel Gauthier, MD, Andre Bieniarz, MD, Steven Warsof, MD (Site not responding. Last check: 2007-10-24)*
		Embryologically, the urachus is a derivative of the allantois.
		The allantois appears on day 16 post-conception as an outpouching of the caudal wall of the yolk sac.
		Occasionally, trace remnants of the allantois remain in the proximal umbilicus and may be seen between the umbilical arteries on pathologic examination of fetuses at this gestational age.
	www.thefetus.net /page.php?id=166 (1191 words)

	Blood-borne seeding by hematopoietic and endothelial precursors from the allantois -- Caprioli et al. 95 (4): 1641 -- ...
		Blood-borne seeding by hematopoietic and endothelial precursors from the allantois
		The allantois retrieved as a presumptive territory (i.e., a fragment of the splanchnopleura) or as a bud produced HSC, thus
		implication is that the allantois, an emanation of the grafted
	www.pnas.org /cgi/content/full/95/4/1641 (3822 words)

	[No title]
		In birds and reptiles, the allantois becomes a large sac, which is filled with stored toxic metabolic by-products from the developing embryo.
		The outer mesodermal layer of the allantois often reaches and fuses with the (inner) mesodermal layer of the chorion.
		In humans, for instance, it functions in early blood formation and in the formation of the urinary bladder (although the sac itself is said to be vestigal).
	www.csc.edu /mathsci/akrejci/BIOL432-532/ck72hr.htm (812 words)

	Development and Preservation of Embryos (Site not responding. Last check: 2007-10-24)
		The extraembryonic membranes are the yolk sac, amnion, allantois, and chorion.
		The allantois also stores excretions, absorbs albumen used as food by the embryo, and absorbs calcium from the shell for the structural needs of the embryo.
		The allantois ceases to function when the chick punctures the air cell and starts to breathe on its own.
	il-traill.outreach.uiuc.edu /poultrynet/development.htm (1189 words)

	UROGENITAL SYSTEM
		It is induced by the mesenchyme of the nephrotome to form branches as it grows back along the rest of the mesenchyme of the nephrotome and these branches induce the mesonephric kidney nephrons, forming a separate organ.
		There is a complex development of cloaca and then separation into two parts- hindgut and UG sinus, then urethra (the connection between the allantois and the UG sinus) and vagina form separately from an opening-up of the base of the UG sinus so that now both open independently to the outside.
		The oviduct bases fuse with the uterus and cervex and that fuses with the vagina which forms partly by an evagination from the UG sinus and has a dual endodermal and mesodermal origin.
	www.csun.edu /~vcbio001/ugsys.html (1102 words)

	Loss of Tbx4 blocks hindlimb development and affects vascularization and fusion of the allantois -- Naiche and ...
		The allantois of the wild-type embryo has formed a vascular umbilicus connecting it to the placenta (p), whereas the mutant embryo is loose in the yolk sac and the allantois has formed only a small, amorphous stump.
		The differentiative capacity of the allantois in the absence
		Extension of the allantois from the posterior axis of the embryo
	dev.biologists.org /cgi/content/full/130/12/2681 (8614 words)

	Developmental Biology Online: Alternative Sources Of Angioblasts
		In the chick, somitic mesoderm may play a role in producing angioblasts, and in the mouse, the allantois has the potency to contribute angioblasts.
		Caprioli and colleagues (1998) have shown the emergence of both hematopoietic and endothelial precursors in the avian allantoic bud.
		The most likely explanation is that the allantois was providing hemangioblasts to the host embryo.
	www.devbio.com /printer.php?ch=15&id=156 (454 words)

	Amniote Egg
		Inside the egg are a series of fluid-filled membranes which permit the embryo to survive: the amnion, allantois, yolk sac, and chorion.
		The allantois and yolk are attached to the reptile embryo.
		The allantois and yolk sac become the umbilical cord, providing a connection through which food reaches the fetus, and wastes are removed.
	www.biologycorner.com /worksheets/amniote-egg.html (487 words)

	Tiger: Raggin' & Rantin': Making Kang A Roo
		Both the yolk sac and the allantois can become partly vascularised and involved in the exchange of respiratory gases.
		In viviparous mammals the yolk sac and/or the allantois become placentae and involved in exchange of nutrients between the foetus and the mother.
		The eggs of kangaroos and other marsupials have a full set of shell membranes, as found in reptiles and birds, but they are much reduced.
	tig.mu.nu /archives/008976.html (302 words)

	Abnormal adherence junctions in the heart and reduced angiogenesis in transgenic mice overexpressing mutant type XIII ...
		The mutant fetus (D) is also well into the turning process, but still has an unfused allantois (a in insert of D), despite being beyond the 7−10 somite stage when fusion normally takes place.
		Strong type XIII collagen staining is seen in the ectoplacental cone (arrowheads and e in insert), which is formed after fusion of the chorion and allantois.
		The insert shows the same area stained by hematoxylin−eosin where the distinct structures of the ectoplacental cone (e) and the labyrinth layer of the placenta (l) can be appreciated.
	www.nature.com /emboj/journal/v20/n18/fig_tab/7594009f3.html (355 words)

	American Zoologist: Stress responses in avian embryos
		The avian allantois is a depot for important metabolites and messenger substances which seems to be controlled by as yet unidentified hormones.
		Probably, a major reason for the dearth of data has been the wide-spread belief that the allantois is merely a respiratory organ and a dumping ground for metabolic wastes.
		During the past five years, we have analyzed the presence of messenger substances and metabolites in blood and amniotic fluid, and in particular in the allantoic fluid of the chicken embryo (Epple et al., 1992; Gill et al., 1994; Ten Busch et al., 1997 a, b; Piechotta et al., 1998).
	www.findarticles.com /p/articles/mi_qa3746/is_199712/ai_n8780937 (1155 words)

	Teaching File Case#29: Watery Navel Discharge (Site not responding. Last check: 2007-10-24)
		The urachus develops from the allantois and the ventral portion of the cloaca, the latter eventually forming the bladder.
		The allantois, a portion of the yolk sac that extnds into the body sac, involutes by the third month of gestation.
		The remainder of the urachus persists as an epithelial lined tubular structure that elongates as the fetal bladder descends from the abdomen in the true pelvis.
	www.uab.edu /pedradpath/case29.html (256 words)

	chorion -- Encyclopædia Britannica
		The allantois, a tube of endoderm (the innermost germ layer), grows out of the early yolk sac in a region that soon becomes the hindgut.
		As the ventral body wall closes in, the yolk stalk and allantois are brought together, along with their mesodermal sheaths and blood vessels (,).
		From the end of the embryo's digestive tract the allantois, an endodermal sac, grows between the amnion and the chorion.
	www.britannica.com /eb/article-9082354?tocId=9082354 (573 words)

	Abstracts / Vasculogenesis in the Murine Allantois / MRDDRC / Waisman Center (Site not responding. Last check: 2007-10-24)
		Despite such long overdue recognition, study of the placenta remains a critically neglected area of embryological study, all the more serious as improper formation of the placenta may be a major contributor to birth defects.
		Although correct formation and differentiation of the allantois is essential for fetal health and survival, a total of only three papers on allantoic development are available in the current literature.
		Further, in the rat, morphological differentiation in the allantois appears to occur first in the distal region before spreading to the base.
	www.waisman.wisc.edu /www/mrddrc/proj011.html (365 words)

	[No title] (Site not responding. Last check: 2007-10-24)
		This brings the capillaries of the allantois into direct contact with the shell membrane, allowing calcium reabsorption from the shell.
		The allantois differs from the amnion and chorion in that it arises within the body of the embryo.
		The allantois serves as a respiratory organ and as a reservoir for the excreta.
	ulisse.cas.psu.edu /4hembryo/physiology.html (641 words)

	WiSSPers, Spring 93, page 2
		It is derived from early embryonic structures -- the yolk sac and the allantois -- which otherwise are, for the most part, vestigial structures in placentated mammals.
		Initially two arteries and two veins arise from the primitive allantois, but by around the 6th week of gestation the right umbilical vein is obliterated.
		The allantois gives rise to the cloaca and part of the bladder; in addition it extends into the body stalk eventually giving rise to a portion of the cord.
	www.wisc.edu /wissp/wisspers/wisspex3.htm (1838 words)

	Bone morphogenetic protein 4 in the extraembryonic mesoderm is required for allantois development and the localization ...
		Bone morphogenetic protein 4 in the extraembryonic mesoderm is required for allantois development and the localization and survival of primordial germ cells in the mouse -- Fujiwara et al.
		periphery of the incipient allantois bud, abutting the exocoelom
		as allantois in the absence of Bmp4 expression in the ExM (Fig.
	www.pnas.org /cgi/content/full/98/24/13739 (4612 words)

	UrologyHealth.org - Adult Conditions - Bladder - Urachal Anomalies (Site not responding. Last check: 2007-10-24)
		The bladder, located in the lower abdomen, is formed from structures located in the lower half of the developing fetus that are directly connected to the umbilical cord.
		The internal part of the allantois is connected to the top of the developing bladder, and in ordinary circumstances, collapses and becomes a cord-like structure called the urachus.
		The formation and regression of this connection from the top of the bladder to the bellybutton are completed by the middle of the second trimester of pregnancy (approximately 20 weeks).
	www.urologyhealth.org /adult/index.cfm?cat=03&topic=141 (2425 words)

	[No title]
		The outer fetal membrane is the allantochorion, which is formed by fusion of the chorion and allantois.
		The chorion opposes the endometrium, while the allantois borders the allantoic space with its allantoic fluid.
		The second fetal membrane is the allantoamnion formed by the fusion of amnion and allantois.
	www.afip.org /CLDavis/GrossCourse99/Placenta.doc (2030 words)

	Untitled Document (Site not responding. Last check: 2007-10-24)
		The allantois is now visible, the somites are completely to the tail and the tail has now completely formed to curved.
		The allantois is visible and the eyes are pigmented and bigger.
		It does not seem effect the development of the head, eye, limb bud, ear, allantois, and ear during the stages that I experimented the embroys.
	www.math.lsa.umich.edu /mmss/archive-2003/Embryology-Tosney/nblake/html (1303 words)

	Development of Urinary Bladder (Site not responding. Last check: 2007-10-24)
		The first of these is the cranial portion which is continuous with the allantois and forms the bladder proper.
		The bladder is initially continuous with the allantois.
		The urachus goes from the umbilicus to the apex of the bladder and forms the median umbilical ligament which can be seen in adults.
	sprojects.mmi.mcgill.ca /embryology/ug/Kidney_Stuff/Normal_Development/Bladderdev.html (307 words)

	Investigation into a role for the primitive streak in development of the murine allantois -- Downs et al. 131 (1): 37 ...
		the distal region of the allantois, farthest from the streak.
		(C) The allantois has been microsurgically removed and, in the subsequent hypothetical scenario, BMP4-positive mesoderm from the yolk sac and amnion crawls onto the exposed primitive streak, thereby re-establishing the BMP4 expression pattern of the normal 0B stage in A, and subsequently that of B in the regenerates.
		That most of the label is in the allantois and not the chorion was revealed by cutting the allantois away from the chorion and re-examining it (not shown).
	dev.biologists.org /cgi/content/full/131/1/37 (9161 words)

	Karen M. Downs, Ph.D. / Faculty / Waisman Center (Site not responding. Last check: 2007-10-24)
		Morphogenesis of the chorio-allantoic placenta involves union between the allantois and the chorion, two tissues initially separated in the conceptus.
		Using a combination of embryo microsurgery and transplantation, histology, immunohistochemistry, genetics and molecular biology, we are elucidating t he genetic and molecular mechanisms by which allantoic mesoderm is converted into the umbilical vasculature, and the mechanisms by which the allantois unites with the chorion to form the placenta.
		It is anticipated that results of this research program will lead to a unified understanding of the relationship between placentation and fetal development, resulting in amelioration and management of birth defects.
	www.waisman.wisc.edu /faculty/downs.html (390 words)

	UW Anatomy Department (Site not responding. Last check: 2007-10-24)
		The allantois will become the umbilical cord whilst the chorion, together with the ectoplacental cone in the mouse, will become the mature chorionic disk.
		Current projects are designed to discover the genetic pathways, environmental cues, and cell-cell and molecular interactions that orchestrate differentiation of allantoic mesoderm into the umbilical vasculature, as well as the major events that regulate union between the allantois, chorion and ectoplacental cone.
		Methods of transplantation, whole embryo culture, explants, genetics, molecular biology and gene discovery by microarray analysis are being used in all aspects of this research program.
	www.anatomy.wisc.edu /faculty_downs.html (278 words)

	Reptiles
		Reptiles have three extraembryonic membranes the chorion, amnion and allantois.
		The chorion and allantois are vascularized membranes that lie against the shell.
		The allantois develops as an outgrowth of the hindgut.
	cas.bellarmine.edu /tietjen/images/reptiles.htm (720 words)

	When does life begin?
		"The chorion, the amnion, the yolk sac, and the allantois constitute the fetal membranes.
		They develop from the zygote but do not participate in the formation of the embryo or fetus — except for parts of the yolk sac and allantois.
		The allantois forms a fibrous cord that is known as the urachus in the fetus and the median umbilical ligament in the adult.
	www.lotusbirth.com /doc/FEB2003Lotusbirth-650.htm (208 words)

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