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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. The germinal stage takes around 10 days. [1] During this stage, the zygote divides in a process called cleavage.
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 ...
The embryo and subsequent early fetus appear to be sexually indifferent, looking neither like a male or a female. Over the next several weeks, hormones are produced that cause undifferentiated tissue to transform into either male or female reproductive organs. This process is called sexual differentiation.
An embryo is the initial stage of development for a multicellular organism.In organisms that reproduce sexually, embryonic development is the part of the life cycle that begins just after fertilization of the female egg cell by the male sperm cell.
In embryology, Carnegie stages are a standardized system of 23 stages used to provide a unified developmental chronology of the vertebrate embryo.. The stages are delineated through the development of structures, not by size or the number of days of development, and so the chronology can vary between species, and to a certain extent between embryos.
Weeks and months are numbered by gestation. Different terms are used to describe prenatal development , meaning development before birth . A term with the same meaning is the "antepartum" (from Latin ante "before" and parere "to give birth") Sometimes "antepartum" is however used to denote the period between the 24th/26th week of gestational ...
The ova, which are the female sex cells, are much larger than the spermatozoon and are normally formed within the ovaries of the female fetus before birth. They are mostly fixed in location within the ovary until their transit to the uterus, and contain nutrients for the later zygote and embryo.
Sexual differentiation is the process of development of the sex differences between males and females from an undifferentiated zygote. [1] [2] Sex determination is often distinct from sex differentiation; sex determination is the designation for the development stage towards either male or female, while sex differentiation is the pathway towards the development of the phenotype.