Gastrulation mesoderm

The blastocyst is a hollow, fluid-filled ball of approximately 1000 cells. The cells that form the outer layer are referred to as trophoblasts and will ultimately develop as extraembryonic tissues (e.g., placenta), while the cells of the inner cell mass are omnipotent (i.e., stem cells) and form the embryo. Depending on the species, the blastocyst arrives at the uterus within 5-10 days of fertilization, whereupon it hatches from the zona pellucida and implants into the uterine wall, which has been preconditioned by ovarian-derived steroid hormones (see Chapter 33). Shortly after implantation, the inner cell mass undergoes gastrulation to form a trilaminar embryo composed of three primary germ layers, the ectoderm, mesoderm, and endoderm. 

C. Genes Regulating Mesoderm Invagination concertina, folded gastrulation, Rbo, RhoCEF... 

Tam, P.P.L., Goldman, D., Camus, A., Schoenwolf, G.C. 2000. Early events of somitogenesis in higher vertebrates Allocation of precursor cells during gastrulation and the organization of a meristic pattern in the paraxial mesoderm. Curr. Top. Dev. Biol. 47, 1-32. 

Yamaguchi, T.P., Harpal, K., Henkemeyer, M., Rossant, J. 1994. fgfr-1 is required for embryonic growth and mesodermal patterning during mouse gastrulation. Genes Dev. 8, 3032-3044. 

Ang, S.L., Jin, O., Rhinn, M., Daigle, N., Stevenson, L., Rossant, J. 1996. A targeted mouse Otx2 mutation leads to severe defects in gastrulation and formation of axial mesoderm and to deletion of rostral brain. Development 122, 243-252. 

The blastoderm comprises two layers of cell, the upper layer or epiblast known as the ectoderm, and the lower layer or hypoblast known as the endoderm (Fig. 12.3fl). Gastrulation begins with the formation of the middle layer, known as the mesoderm, and it is from blocks of mesoderm that the somites arise and the segmentation pattern is developed. Segmentation... 

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