The blastocyst is an advanced stage of embryo development where the embryo differentiates into two cell lines, the inner cell mass and the trophectoderm, and forms a fluid filled cavity (Blastocoel
In human apical trophoblast cells, mitochondria are elongated, with transverse cristae, and are largely peripherally located , plausibly to facilitate the energetically costly process of blastocoel
expansion and zona hatching .
were observed and developed quickly to the gastrula stage within 2 days.
Blastocyst--The blastocyst consists of a sphere made up of an outer layer of cells (the trophectoderm), a fluid-filled cavity (the blastocoel
), and a cluster of cells on the interior (the inner cell mass).
Although cleavage divisions were affected only at very high DMAE concentrations, embryos treated with lower concentrations at the two-cell stage subsequently developed malformations (Figure 3): overabundance of mesenchyme-like cells that accumulated first in the vegetal half of the blastocoel
, and later occupied all of the blastocoel
, blocking or inhibiting gastrulation; absence of a second pair of arms in mid-pluteus, or sometimes shortening or absence of one arm of the first pair (Figure 3H).
Some features of early embryos (the blastocoel
, the archenteron of the gastrula) could be seen in specimens pressed gently between a glass slide and coverslip.
The newly formed morula itself begins to change, as the cells that comprise its trophoblast secrete a fluid which, because of the tight junctions between the trophoblastic cells on the morula's external wall, remains inside the morula, causing by this "cavitation" a fluid-filled cavity called the "blastocoel
" to exist inside the morula.
Furthermore, the accumulation of hypertonic fluid within the blastocoel
is in part due the action of the Na+/K+ ATPase pump (20).
At 51 h PF, mesenchymal cells can be seen inside the blastocoel
, near the base of the archenteron (Fig.
During embryonic genome activation, mitochondria progressively undergo functional and structural changes, and also generate higher levels of ATP to supply the increasing energy demands of the embryo that result from RNA and protein synthesis and blastocoel
formation (Khurana and Niemann, 2000).
The blastocyst contains three distinct areas: the trophoblast, which is the surrounding outer layer that later becomes the placenta, the blastocoel
, which is a fluid-filled cavity within the blastocyst, and the inner cell mass, which becomes the embryo proper.
During ingression, the motion of cells from the wall of the blastula into the blastocoel
is accompanied by changes in the expression of cell surface receptors.
Ciliated, swimming blastulae with a small blastocoel
were formed about 16 h after fertilization (Fig.
These differences are also shown in Figure 4A to E, where the HP or HA exposed groups exhibited embryo developmental morphology, blastocoel
cavity expansion, and embryo quality that were superior to the control.
was not visible within the blastula, suggesting that J.