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Diagram of stages of embryo development to a larval and adult stage. In developmental biology, animal embryonic development, also known as animal embryogenesis, is the developmental stage of an animal embryo. Embryonic development starts with the fertilization of an egg cell (ovum) by a sperm cell (spermatozoon). [1]
A homonculus inside a sperm cell, as drawn by Nicolaas Hartsoeker in 1695 Jan Swammerdam, Miraculum naturae sive uteri muliebris fabrica, 1729. In the history of biology, preformationism (or preformism) is a formerly popular theory that organisms develop from miniature versions of themselves.
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 36 weeks. The germinal stage refers to the time from fertilization through the development of the early embryo until implantation is completed in the uterus .
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 ]
Diagram showing the process by which the intestine rotates and herniates during normal development. From panel A to B (left-sided views), the midgut loop rotates 90° in a counterclockwise direction (caudal-to-rostral view), so that its position changes from midsagittal (A) to transverse (B1). The small intestine forms loops (B2) and slides ...
1. Add to Grains. Turn yesterday’s soup into today’s healthy bowl. Start with a base of grains like rice, farro, or quinoa. Add roasted veggies and a protein.
The NHTSA's Office of Defects Investigation said it had received one complaint alleging a crash when the feature was being used and had reviewed at least three media reports of similar crashes ...
1. Dyker Heights: Brooklyn, New York, U.S. OlegAlbinsky/Getty Images. Renowned for its lavish holiday decorations, homeowners in this affluent Brooklyn neighborhood have been known to spend ...