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Embryonic development in the human, covers the first eight weeks of development; at the beginning of the ninth week the embryo is termed a fetus. The eight weeks have 23 stages. 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 ...
Some degree of weight gain is expected during pregnancy. The enlarging uterus, growing fetus, placenta, amniotic fluid, normal increase in body fat, and increase in water retention all contribute weight gain during pregnancy. The amount of weight gain can vary from 5 pounds (2.3 kg) to over 100 pounds (45 kg).
Head hair becomes coarse and thicker. Birth is imminent and occurs around the 38th week after fertilization. The fetus is considered full-term between weeks 37 and 40 when it is sufficiently developed for life outside the uterus. [ 14][ 15] It may be 48 to 53 cm (19 to 21 in) in length when born.
Amniotic sac. The amniotic sac, also called the bag of waters[ 1][ 2] or the membranes, [ 3] is the sac in which the embryo and later fetus develops in amniotes. It is a thin but tough transparent pair of membranes that hold a developing embryo (and later fetus) until shortly before birth. The inner of these membranes, the amnion, encloses the ...
A lithopedion. This highly unusual specimen remained in the abdomen of a woman for 2 years. A lithopedion ( also spelled lithopaedion or lithopædion; from Ancient Greek: λίθος "stone" and Ancient Greek: παιδίον "small child, infant"), or stone baby, is a rare phenomenon which occurs most commonly when a fetus dies during an ...
The fetal membranes separate maternal tissue from fetal tissue at a basic mechanical level. The fetal membrane is composed of a thick cellular chorion covering a thin amnion composed of dense collagen fibrils. The amnion is in contact with the amniotic fluid and ensures structural integrity of the sac due to its mechanical strength.
e. The fetal endocrine system is one of the first systems to develop during prenatal development of a human individual. The endocrine system arises from all three embryonic germ layers. The endocrine glands that produce the steroid hormones, such as the gonads and adrenal cortex, arise from the mesoderm. In contrast, endocrine glands that arise ...
Fetal Thymus growth. At 8 weeks of gestation when the fetus weighed 1 gram, the thymus could not be detected. In many of the 39 fetuses weighing around 1.3-14.7 grams, the thymus tissues could not be dissected by the group especially in the smaller fetuses due to its non-detection. Fetuses weighing more than or equal to 5 grams could be detected.