The Eighth Day of Life in a Mammal

For some reason I always seem to miss the fireworks every year. That’s okay though, since I spend a lot of time using fluorescent stains for various cell types.

Above is a bovine embryo (cow) at eight days just before it "hatches." Hatching, for mammalian embryos, is when the cells you see will be extruded from the surrounding zona pellucida. Each glowing blue oval is the nucleus of a cell. Near the 10:00 position, in this photo, is a heavy grouping of these cells and this represents the inner cell mass (ICM). The ICM cells will become the embryo and this ICM is unique to mammalian embryos. The other cells will make up the trophoblast or trophectoderm. The trophectoderm will invade the uterine wall and become the placenta. The ICM and the trophectoderm remain connected by a strand of tissue that will become the umbilical cord.

If you look close to the center of this embryo, you can see a brighter nucleus that is not oval shaped. This is a cell that is undergoing division and the chromosomes have condensed. There are a few more of these if you look around. (Click on the image for a larger picture)

I used a Nikon Coolpix L1 by simply holding it up to one of the eyepieces of a fluorescent microscope and snapped the picture. Cheap and peppy!

Who needs fireworks when you have a fluorescent microscope?

- Just a peasant