Germ layers  [Interactive video text]

The mesoderm which is associated with the primitive streak which is also called secondary mesoderm insinuates itself between the ectoderm and the endoderrn mainly around the middle part of the germ disc and and also the areas cranial to the prochordal plate and caudal to the cloaca.

Surrounding the germ disc is the primary mesoderm which fuses with the secondary mesoderm and as development continues, there is a break in the mesoderm to form the intraembryonic celom. There then forms a breakage in the primary mesoderm that separates the extraembryonic coelom from the intraembryonic celom. This leads to communication between the intra and extra embryonic celom The primary mesoderm breaks to form the extraembryonic coelom. Secondary mesoderm is formed from the primitive streak. The mesoderm formed from the primitive streak aggregate itself into paraxial mesoderm, lateral plate mesoderm which is the mesoderm of the body cavity divided into a superior somatopleuric mesoderm (close to ectodermal cavity) and an inferior splanchnopleuric mesoderm (close to endodermal cavity). Between the two is the intraembryonic celom. Also between the lateral plate and the paraxial mesoderm is the intermediate cell mass.

The mesoderm gives rise to the connective tissues of the body, smooth and striated muscles, and cardiac muscles, urogenital system, cartilage and ligaments and the reticuloendothelial system.















Oluwole Ogunranti

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