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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 .
Oogenesis (/ ˌ oʊ. ə ˈ dʒ ɛ n ɪ s ɪ s /) or ovogenesis is the differentiation of the ovum (egg cell) into a cell competent to further develop when fertilized. [1] It is developed from the primary oocyte by maturation. Oogenesis is initiated before birth during embryonic development.
Interareal differences exhibit a temporal hourglass pattern, dividing human neocortical development into three major phases. During the first phase, in the first six months after conception, general architecture of brain regions is largely formed by a burst of genetic activity, which is distinct for specific regions of the neocortex.
During fetal development, divisions of the neural tube that give rise to the hindbrain (rhombencephalon) and the other primary vesicles (forebrain and midbrain) occur at 28 days after conception. With the exception of the midbrain, these primary vesicles undergo further differentiation at 5 weeks after conception to form the myelencephalon and ...
Flowering plants (angiosperms) create embryos after the fertilization of a haploid ovule by pollen. The DNA from the ovule and pollen combine to form a diploid, single-cell zygote that will develop into an embryo. [21] The zygote, which will divide multiple times as it progresses throughout embryonic development, is one part of a seed.
The term "conception" refers variably to either fertilization or to formation of the conceptus after its implantation in the uterus, and this terminology is controversial. The zygote will develop into a male if the egg is fertilized by a sperm that carries a Y chromosome, or a female if the sperm carries an X chromosome. [5]
Development before birth, or prenatal development (from Latin natalis ' relating to birth ') is the process in which a zygote, and later an embryo, and then a fetus develops during gestation. Prenatal development starts with fertilization and the formation of the zygote , the first stage in embryonic development which continues in fetal ...
These brain vesicles further divide into subregions. The prosencephalon gives rise to the telencephalon and diencephalon, and the rhombencephalon generates the metencephalon and myelencephalon. The hindbrain, which is the evolutionarily most ancient part of the chordate brain, also divides into different segments called rhombomeres.