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Diagrams to show the development of male and female generative organs from a common type. A.—Diagram of the primitive urogenital organs in the embryo previous to sexual distinction. 3. Ureter. 4. Urinary bladder. 5. Urachus. cl. Cloaca. cp. Elevation which becomes clitoris or penis. i. Lower part of the intestine. ls.
Human embryology is the study of this development during the first eight weeks after fertilization. The normal period of gestation (pregnancy) is about nine months or 40 weeks. The germinal stage refers to the time from fertilization through the development of the early embryo until implantation is completed in the uterus .
The yolk sac is the first element seen within the gestational sac during pregnancy, [1] usually at three days gestation. The yolk sac is situated on the front ( ventral ) part of the embryo ; it is lined by extra-embryonic endoderm , [ 3 ] outside of which is a layer of extra-embryonic mesenchyme , derived from the epiblast.
The theory of recapitulation, also called the biogenetic law or embryological parallelism—often expressed using Ernst Haeckel's phrase "ontogeny recapitulates phylogeny"—is a historical hypothesis that the development of the embryo of an animal, from fertilization to gestation or hatching (), goes through stages resembling or representing successive adult stages in the evolution of the ...
According to the recapitulation theory, such structures should invariably be present in frogs because they were assumed to be at a lower level in the evolutionary tree. Von Baer concluded that while structures like the notochord are recapitulated during embryogenesis, whole organisms are not. [ 7 ]
"I was like, 'Oh my god I'm gonna smell like diapers and cheddar bunnies.' So I was like, I'll get a new perfume," Gilpin said. "And Seth, when I tell you I doused myself with this perfume ...
(Reuters) -U.S. stock futures rose ahead of an interest-rate decision by the Federal Reserve on Thursday, building on a sharp rally set off by Donald Trump's stunning comeback as U.S. president ...
The lateral plate mesoderm is the mesoderm that is found at the periphery of the embryo.It is to the side of the paraxial mesoderm, and further to the axial mesoderm.The lateral plate mesoderm is separated from the paraxial mesoderm by a narrow region of intermediate mesoderm.