Gestational sac

The gestational sac is the large pit of fluid surrounding the embryo. During early embryogenesis it consists of the extraembryonic coelom, besides called the chorionic cavity. The gestational theca is normally contained within the uterus. It is the lone available social organization that can be used to determine if an intrauterine pregnancy exists until the embryo can be identified. On obstetric sonography, the gestational sac is a darkness ( “ anechoic ” ) outer space surrounded by a egg white ( “ hyperechoic ” ) rim .

structure [edit ]

The gestational sac is ball-shaped in human body, and is normally located in the upper part ( fundus ) of the uterus. By approximately nine weeks gestational senesce, the amniotic sauk has expanded to occupy the majority of the volume of the gestational pouch, finally expanding to reduce the extraembryonic celom to a thin layer between the amnion membrane and the mesoderm. By then, the gestational theca is normally merely called the “ amniotic sac ” .

Development [edit ]

During embryogenesis, the extraembryonic coelom ( or chorionic cavity ) that constitutes the gestational sauk is a share of the embryo consist of a cavity between Heuser ‘s membrane and the trophoblast.

During formation of the primitive egg yolk pouch, some of the migrate endoderm cells differentiate into mesenchymal cells that fill the space between Heuser ‘s membrane and the trophoblast, forming the extraembryonic mesoderm. As development progresses, belittled lacuna begin to form within the extraembryonic mesoderm which enlarge to become the extraembryonic celom. The extraembryonic celom divides the extraembryonic mesoderm into two layers : extraembryonic splanchnopleuric mesoderm, which lies adjacent to Heuser ‘s membrane around the outside of the crude yolk sac, and extraembryonic somatopleuric mesoderm, which lies adjacent to the cytotrophoblast layer of the embryo. The chorionic cavity is enclosed by the chorionic plate, which is composed of an inner layer of somatopleuric mesoderm and an forbidden level of trophoblast cells .

clinical meaning [edit ]

sonography [edit ]

[1] Mean gestational sac diameter by gestational age. The gloomy agate line is the average, and the green area delimits the 5th and the 95th percentiles

The average pouch diameter [ 2 ] can effectively estimate the gestational old age [ 3 ] between 5 and 6 weeks, with an accuracy of about +/- 5 days. [ 4 ] The egg yolk sauk and embryo should be promptly identifiable when the gestational pouch reaches a certain size — a yolk pouch should be seen when the gestational sac is 20mm and a fetal pole should be seen when the gestational sac reaches 25mm. gestational sac can be identified via ultrasound and are broadly identified by the pursue four characteristics :

1. The sac has a round or elliptical shape in longitudinal and transverse views
2. The sac is surrounded by a white echogenic rim (choriodecidual reaction) [5]
3. The sac is located in the uterine fundus
4. The sac is not implanted on the midline, but eccentrically (to one side of the uterine cavity line).

References [edit ]

• Media related to Gestational sac at Wikimedia Commons

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