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The placenta (pl.: placentas or placentae) is a temporary embryonic and later fetal organ that begins developing from the blastocyst shortly after implantation.It plays critical roles in facilitating nutrient, gas and waste exchange between the physically separate maternal and fetal circulations, and is an important endocrine organ, producing hormones that regulate both maternal and fetal ...
Most mammals first form a temporaty choriovitelline placenta, then the chorioallantoic placenta takes over. (Primates do not form a definite choriovitelline placenta by fusion, but strong expression conservation suggest that the yolk sac remains useful.) [7] Marsupials mostly have choriovitelline placental tissue. Rodents maintain both types ...
If implantation occurs, the corpus luteum will continue to produce progesterone for eight to twelve weeks, after which the placenta takes over this function. [6] In the absence of fertilization, hCG is not produced and the corpus luteum will atrophy in 10–12 days (Luteolysis or luteal regression).
However, in placental animals such as humans, the placenta eventually takes over progesterone production and the corpus luteum degrades into a corpus albicans without embryo/fetus loss. [ citation needed ]
The embryo, the extra-embryonic membranes, and the placenta are collectively referred to as a conceptus, or the "products of conception". Rapid growth occurs and the embryo's main features begin to take form. This process is called differentiation, which produces the varied cell types (such as blood cells, kidney cells, and nerve cells).
The role of the placenta in progestogen production varies by species. In the sheep, horse, and human, the placenta takes over the majority of progestogen production, whereas in other species the corpus luteum remains the primary source of progestogens. In the sheep and human, progesterone is the major placental progestogen.
Now, researchers are finding them in almost every part of the human body, including in breast milk, the placenta, testicles, hearts, livers, and kidneys. ... Over the past century, ...
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).