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A fetus or foetus ( / ˈfiːtəs /; pl.: fetuses, foetuses, rarely feti or foeti) is the unborn offspring that develops from a mammal embryo. [ 1] Following embryonic development, the fetal stage of development takes place.
Human embryonic development or human embryogenesis is the development and formation of the human embryo. It is characterised by the processes of cell division and cellular differentiation of the embryo that occurs during the early stages of development. In biological terms, the development of the human body entails growth from a one-celled ...
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 . In human pregnancy, prenatal development ...
A fetus is a stage in the human development considered to begin nine weeks after fertilization. [4] [5] In biological terms, however, prenatal development is a continuum, with many defining features distinguishing an embryo from a fetus. A fetus is also characterized by the presence of all the major body organs, though they will not yet be ...
During continued fetal development, the early body systems, and structures that were established in the embryonic stage continue to develop. Sex organs begin to appear during the third month of gestation. The fetus continues to grow in both weight and length, although the majority of the physical growth occurs in the last weeks of pregnancy.
The fetus reaches a length of about 40–48 cm (16–19 in). The fetus weighs about 2.5 to 3 kg (6 lb 10 oz)to 6 lb 12 oz). Lanugo begins to disappear. Body fat increases. Fingernails reach the end of the fingertips. A baby born at 36 weeks has a high chance of survival, but may require medical interventions. Fetus at 38 weeks after fertilization.
Embryo. 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. The resulting fusion of these two cells produces a single-celled zygote that undergoes ...
Implantation (embryology) Implantation, also known as nidation, [1] is the stage in the mammalian embryonic development in which the blastocyst hatches, attaches, adheres, and invades into the endometrium of the female's uterus. [2] Implantation is the first stage of gestation, and, when successful, the female is considered to be pregnant. [3]