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Prenatal development (from Latin natalis 'relating to birth') involves the development of the embryo and of the fetus during a viviparous animal's gestation. Prenatal development starts with fertilization , in the germinal stage of embryonic development, and continues in fetal development until birth .
Pregnancy is the period of time during which the fetus develops, dividing via mitosis inside the uterus. During this time, the fetus receives all of its nutrition and oxygenated blood from the mother, filtered through the placenta , which is attached to the fetus' abdomen via an umbilical cord .
Gestational age is the time that has passed since the onset of the last menstruation, which generally or as standard occurs 2 weeks before the actual fertilization. Embryonic age, in contrast measures the actual age of the embryo or fetus from the time of fertilization. Nevertheless, menstruation has historically been the only means of ...
Development at birth varies considerably among animals, and even among mammals. Altricial species are relatively helpless at birth and require considerable parental care and protection. In contrast, precocial animals are born with open eyes, have hair or down, have large brains, and are immediately mobile and somewhat able to flee from, or ...
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.
Mammals during pregnancy can have one or more gestations at the same time, for example in a multiple birth. [2] The time interval of a gestation is called the gestation period. In obstetrics, gestational age refers to the time since the onset of the last menses, which on average is fertilization age plus two weeks. [3]
Major secondary sexual characteristics include a larger, more muscular stature, deepened voice, facial and body hair, broad shoulders, and the development of an Adam's apple. [5] An important sexual hormone of males is androgen, particularly testosterone. [6] The testes release a hormone that controls the development of sperm.
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 ...