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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.
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 age until birth, for example in antepartum ...
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 ...
Tooth buds, which will form the baby teeth, appear. The limbs are long and thin. The fetus can make a fist with its fingers. Genitals appear well differentiated. Red blood cells are produced in the liver. Heartbeat can be detected by ultrasound. [7]
The way to measure a baby's length is to lay the baby down and stretch a measuring tape from the top of the head to the bottom of the heel. Weight In developed countries, the average birth weight of a full-term newborn is approximately 3.4 kg ( 7 + 1 ⁄ 2 lb), and is typically in the range of 2.7–4.6 kg (6.0–10.1 lb).
The third membrane is the allantois, and the fourth is the chorion which surrounds the embryo after about a month and eventually fuses with the amnion. [ 6 ] Amniocentesis is a medical procedure where fluid from the sac is sampled during fetal development , between 15 and 20 weeks of pregnancy, to be used in prenatal diagnosis of chromosomal ...
Fertilization was not understood in antiquity. Hippocrates believed that the embryo was the product of male semen and a female factor. Aristotle held that only male semen gave rise to an embryo, while the female only provided a place for the embryo to develop, [5] a concept he acquired from the preformationist Pythagoras.
The human fetus moves throughout its entire development. Fetal movement refers to motion of a fetus caused by its own muscle activity. Locomotor activity begins during the late embryological stage and changes in nature throughout development. Muscles begin to move as soon as they are innervated.