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Early development differences between deuterostomes versus protostomes. In deuterostomes, blastula divisions occur as radial cleavage because they occur parallel or perpendicular to the major polar axis. In protostomes, the cleavage is spiral because division planes are oriented obliquely to the polar major axis.
Protostome and deuterostome embryos differ in several other ways. Secondary body cavities ( coeloms ) generally form by schizocoely , where the coelom forms out of a solid mass of embryonic tissue splitting away from the rest, instead of by enterocoelic pouching , where the coelom would otherwise form out of in-folded gut walls.
In humans (a deuterostome), the development proceeds differently. The buccopharyngeal membrane is created in the foregut and is perforated during the fourth week of human development, creating the primitive mouth, whereas the cloacal membrane is created in the hindgut and is perforated during the eighth week of human development, creating the ...
The distinction between protostomes and deuterostomes is based on the direction in which the mouth (stoma) develops in relation to the blastopore. Protostome derives from the Greek word protostoma meaning "first mouth" (πρῶτος + στόμα) whereas Deuterostome's etymology is "second mouth" from the words second and mouth ...
A cell can only be indeterminate (also called regulative) if it has a complete set of undisturbed animal/vegetal cytoarchitectural features. It is characteristic of deuterostomes—when the original cell in a deuterostome embryo divides, the two resulting cells can be separated, and each one can individually develop into a whole organism.
Early in development, deuterostome embryos undergo radial cleavage during cell division, while many protostomes (the Spiralia) undergo spiral cleavage. [143] Animals from both groups possess a complete digestive tract, but in protostomes the first opening of the embryonic gut develops into the mouth, and the anus forms secondarily.
The lone CFP first-round game on Friday, Dec. 20 is No. 10 seed Indiana at No. 7 seed Notre Dame at 8 p.m. ET inside Notre Dame Stadium — which also happens to be the first meeting between the ...
The traditional view was that lophophorates were a mix of protostome and deuterostome features. Research from the 1970s onwards suggested they were deuterostomes, because of some features that were thought characteristic of deuterostomes: a three-part coelom; radial rather than spiral cleavage in the development of the embryo; [ 54 ] and ...