Re: yolk sac
From: udaya kumar (udaya@md2.vsnl.net.in)
Fri May 25 20:19:01 2001
Dear Terry,
The extraamniotic space has a fluid that can been aspirated ( Coelocentesis) .
Using FISH probes it appears that Karyotyping is possible at 6weeks gestation.
Made a powerpoint presentation on Coelocentesis in a recent conference. Will
post it to you if you want it.
..Udayakumar
DuboseTerryJ@uams.edu wrote:
> According to Moore & Persaud, DEVELOPING HUMAN: Clinically Oriented
> Embryology, W. B. Saunders, 1993 p. 40-46 & 70-80; what we see
> sonographically is actually the "secondary yolk sac". The "primary yolk
> sac" develops earlier (during 3rd LMP week, i.e. 9 days after conception)
> and is too small to visualize sonographically. The secondary yolk develops
> around conceptual day 13 (start of 4 LMP week).
>
> You are correct in that the yolk is related to the formation of the fetal
> gut. Moore & Persaud has a great graphic representation of this process on
> page 71. The amnion forms around the embryo and separates or "squeezes" the
> yolk sac from the midgut and intraembryonic coelom at about 26-28 post
> conception.
>
> An interesting bit of trivia... I had always wondered what the "choronic
> cavity" outside the amnionic sac contained... I was sure that it was not a
> vacuuume, but could not find any reference other than "cavity". Finally
> during research for FETAL SONOGRAPHY, I found the answer in: Benirschke K;
> "NORMAL DEVELOPMENT", Chapter 4; in Creasy RK and Resnik R, Editors;
> MATERNAL-FETAL MEDICINE: Principles and Practice, 2nd Edition; W. B.
> Saunders Company, 1989; p. 117.
> "As the pregnancy progresses the thin amniotic membrane enlarges and will
> contain the embryo, the yolk sac will remain outside the amnion. See Figure
> 16-12C. The amniotic sac with it's embryo, and the yolk sac are all found
> within the so called "gestational sac". This gestational sac is actually the
> chorionic cavity. The chorionic space around the amniotic sac is filled
> "...by a gel that liquefies upon touching, the magma reticulare." This magma
> reticulare has a slightly echogenic appearance when compared to the very
> clear amniotic fluid; see Figure 16-12C. The magma reticulare is also called
> the "chorioamniotic accumulation" and is a normal finding before the amnion
> and chorion fuse." See: DuBose, FETAL SONOGRAPHY, W. B. Saunders Co., 1996,
> p. 370.
>
> Terry J. DuBose, M.S., RDMS, Assistant Professor
> Director, Diagnostic Medical Sonography Program
> CHRP, University of Arkansas for Medical Sciences
> Little Rock, Arkansas, USA
> 501-686-6510
> http://www.io.com/~dubose/ <http://www.io.com/~dubose/>
> http://www.uams.edu/CHRP/dmshome.htm <http://www.uams.edu/CHRP/dmshome.htm>
>
> http://www.obgyn.net/us/panel/panel.htm
> <http://www.obgyn.net/us/panel/panel.htm>
>
> -----Original Message-----
> From: Dr. N. A. Mohile [mailto:namohile@satyam.net.in]
> Sent: Friday, May 25, 2001 10:42 AM
> To: Multiple recipients of list ULTRASOUND
> Subject: yolk sac
>
> The round structure seen within the gestation sac by 5 weeks and called yolk
> sac is visible even at 12 weeks outside the amniotic sac.Embryologically
> yolk sac forms the gut.Is this structure really yolk sac?
> -Nila.
