File:Stage7 bf5.jpg

Human embryo - 3 week

Appearance of section looks to be about a Carnegie stage 7 embryo.

Original Author Legend - Primitive Trilaminar Human Embryo in Tubal Pregnancy (40X)

"I think this is at about the same developmental stage as the Hertig-Rock embryo of 1945, which has been variously estimated at 16.5 or 19 days postovulation (4 to 5 weeks by conventional obstetrical dating, counting from the first day of the last menstrual period)."

Original file name: 3944578509_bd228ca576_o.jpg

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Uploaded to Flickr on September 22, 2009 by Ed Uthman Image (pathologist in Houston, Texas)

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Human Embryo Stage 7 Information

Carnegie stage 7

Features: embryonic disc, primitive node, primative streak, primitive groove, yolk sac

Facts: Week 3, 15 - 17 days, 0.4 mm

View 1: embryonic disc, showing the epiblast viewed from the amniotic (dorsal) side.

Events: Gastrulation is continuing as cells migrate from the epiblast, continuing to form mesoderm.

Mesoderm lies between the ectoderm and endoderm as a continuous sheet except at the buccopharyngeal and cloacal membranes. These membranes have ectoderm and endoderm only and will lie at the rostral (head) and caudal (tail) of the gastrointestinal tract.