Baby in Sac With Placenta and Umbilical Cord
| Amniotic sac | |
|---|---|
 ten-week-old human fetus surrounded by amniotic fluid inside the amniotic sac | |
| Anatomical terminology [edit on Wikidata] |
The amniotic sac, too called the purse of waters [1] [2] or the membranes,[3] is the sac in which the embryo and later on fetus develops in amniotes. Information technology is a thin but tough transparent pair of membranes that hold a developing embryo (and later fetus) until shortly earlier birth. The inner of these membranes, the amnion, encloses the amniotic cavity, containing the amniotic fluid and the embryo. The outer membrane, the chorion, contains the amnion and is office of the placenta. On the outer side, the amniotic sac is connected to the yolk sac, the allantois, and via the umbilical cord, the placenta.[4]
The yolk sac, amnion, chorion, and allantois are the 4 extraembryonic membranes that lie exterior of the embryo and are involved in providing nutrients and protection to the developing embryo.[5] They form from the inner cell mass; the first to form is the yolk sac followed by the amnion which grows over the developing embryo. The amnion remains an important extraembryonic membrane throughout prenatal development. The 3rd membrane is the allantois, and the fourth is the chorion which surrounds the embryo after well-nigh a calendar month and somewhen fuses with the amnion.[vi]
Amniocentesis is a medical procedure where fluid from the sac is sampled during fetal development, between 15 and 20 weeks of pregnancy, to be used in prenatal diagnosis of chromosomal abnormalities and fetal infections.[7]
Structure [edit]
Amniotic cavity in human being embryo i.iii mm. long
The amniotic cavity is the airtight sac betwixt the embryo and the amnion, containing the amniotic fluid. The amniotic cavity is formed by the fusion of the parts of the amniotic fold, which first makes its appearance at the cephalic extremity and subsequently at the caudal end and sides of the embryo. Equally the amniotic fold rises and fuses over the dorsal aspect of the embryo, the amniotic cavity is formed.[ citation needed ]
Development [edit]
At the commencement of the second week, a cavity appears within the inner prison cell mass, and when it enlarges, information technology becomes the amniotic cavity. The floor of the amniotic cavity is formed by the epiblast. Epiblast migrates betwixt the epiblastic disc and trophoblast. In this mode the epiblastic cells migrate betwixt the embryoblast and trophoblast. The floor is formed past the epiblast which afterwards transforms to ectoderm while the remaining cells which are present betwixt the embryoblast and trophoblast are called amnioblasts (flattened cells). These cells are also derived from epiblast which is transformed into ectoderm.[ commendation needed ]
The amniotic crenel is surrounded past an extraembryonic membrane, called the amnion. As the implantation of the blastocyst progresses, a small space appears in the embryoblast, which is the primordium of the amniotic cavity. Before long, amniogenic (amnion-forming cells) amnioblasts separate from the epiblast and line the amnion, which encloses the amniotic cavity.[ citation needed ]
The epiblast forms the floor of the amniotic cavity and is continuous peripherally with the amnion. The hypoblast forms the roof of the exocoelomic cavity and is continuous with the thin exocoelomic membrane. This membrane along with hypoblast forms the primary yolk sac. The embryonic disc now lies betwixt the amniotic crenel and the main yolk sac. Cells from the yolk sac endoderm form a layer of connective tissue, the extraembryonic mesoderm, which surrounds the amnion and yolk sac.[ commendation needed ]
Birth [edit]
If, after birth, the complete amniotic sac or large parts of the membrane remain coating the newborn, this is called a caul.
When seen in the light, the amniotic sac is shiny and very smooth, but tough.
In one case the baby is pushed out of the mother'due south uterus, the umbilical cord, placenta, and amniotic sac are pushed out in the after nativity.
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The amniotic sac opened during afterbirth test
Function [edit]
The amniotic sac and its filling provide a liquid that surrounds and cushions the fetus. It is a site of exchange of essential substances, such every bit oxygen, between the umbilical cord and the fetus.[8] It allows the fetus to movement freely within the walls of the uterus.[ citation needed ] Buoyancy is as well provided.
Clinical significance [edit]
Chorioamnionitis is inflammation of the amniotic sac (chorio- + amnion + -itis), usually considering of infection. It is a risk factor for neonatal sepsis.
During labor, the amniotic sac must interruption and so that the child can be born. This is known equally rupture of membranes (ROM). Usually, it occurs spontaneously at full term either during or at the offset of labor. A premature rupture of membranes (PROM) is a rupture of the amnion that occurs prior to the onset of labor. An bogus rupture of membranes (AROM), also known equally an amniotomy, may be clinically performed using an amnihook or amnicot in order to induce or to accelerate labour.
The amniotic sac has to be punctured to perform amniocentesis.[9] [10] This is fairly routine procedure, but tin can atomic number 82 to infection of the amniotic sac in a very pocket-sized number of cases.[xi] Infection more commonly arises vaginally.[11] [12]
References [edit]
- ^ Freshwater, Dawn; Masiln-Prothero, Sian (22 May 2013). Blackwell's Nursing Dictionary. ISBN978-one-118-69087-one . Retrieved xi March 2016.
- ^ "Definition of Bag OF WATERS". www.merriam-webster.com . Retrieved six October 2021.
- ^ "Premature rupture of membranes: MedlinePlus Medical Encyclopedia". medlineplus.gov . Retrieved half-dozen October 2021.
- ^ Larsen, WJ (2001). Human being Embryology (3rd ed.). Churchill Livingstone. p. forty. ISBN0-443-06583-seven.
- ^ Wolpert (2015). Principles of development (Fifth ed.). Oxford, United Kingdom. p. 666. ISBN978-0-xix-967814-3.
- ^ Carlson, Bruce M. (2014). "Placenta and Extraembryonic Membranes". Man Embryology and Developmental Biology. pp. 117–135. doi:10.1016/B978-1-4557-2794-0.00007-three. ISBN978-1-4557-2794-0.
- ^ "Amniocentesis". nhs.uk. twenty October 2017. Retrieved 6 October 2021.
- ^ Jarzembowski, J.A. (2014). "Normal Structure and Function of the Placenta". Pathobiology of Human Disease. pp. 2308–2321. doi:x.1016/b978-0-12-386456-7.05001-two. ISBN978-0-12-386457-4.
- ^ Wilde, Colin; Out, Dorothée; Johnson, Sara; Granger, Douglas A. (2013). "Sample Drove, Including Participant Preparation and Sample Handling". The Immunoassay Handbook. pp. 427–440. doi:10.1016/b978-0-08-097037-0.00029-4. ISBN978-0-08-097037-0.
- ^ Carlson, Bruce M. (2014). "Fetal Period and Nativity". Homo Embryology and Developmental Biology. pp. 453–472. doi:ten.1016/b978-1-4557-2794-0.00018-8. ISBN978-1-4557-2794-0.
- ^ a b Jefferson, Kimberly Thou. (2012). "The Bacterial Etiology of Preterm Nativity". Advances in Applied Microbiology Volume 80. Advances in Applied Microbiology. Vol. eighty. pp. i–22. doi:10.1016/b978-0-12-394381-ane.00001-5. ISBN978-0-12-394381-1. PMID 22794142.
- ^ Ariel, I.; Vocalist, D.B. (2014). "Placental Pathologies – Intrauterine Infections". Pathobiology of Human Disease. pp. 2360–2376. doi:x.1016/b978-0-12-386456-7.05007-three. ISBN978-0-12-386457-4.
External links [edit]
- https://world wide web.mun.ca/biology/scarr/Amniotic_egg.html
- http://staff.um.edu.mt/acus1/IMPLANTATION.htm
Source: https://en.wikipedia.org/wiki/Amniotic_sac
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