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Placentation is the formation, type and structure, or modes of arrangement of the placenta. The function of placentation is to transfer nutrients, respiratory gases, and water from maternal tissue to a growing embryo , and in some instances to remove waste from the embryo.
Placentation has also evolved in some reptiles. [9] The mammalian placenta evolved more than 100 million years ago and was a critical factor in the explosive diversification of placental mammals. [10] Although all mammalian placentas have the same functions, there are important differences in structure and function in different groups of mammals.
The cotyledons receive fetal blood from chorionic vessels, which branch off cotyledon vessels into the cotyledons, which, in turn, branch into capillaries. [4] The cotyledons are surrounded by maternal blood, which can exchange oxygen and nutrients with the fetal blood in the capillaries.
Articles relating to the placenta, 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 physiology ...
Eventually, the syncytiotrophoblast comes into contact with maternal blood and forms chorionic villi – the beginning of placentation. Following invasion, the breach in the uterine epithelium made by the blastocyst's entry is sealed by a fibrin plug. The fibrin plug is a coagulation of a blood clot and cellular debris. [11]
Location of ovules inside a Helleborus foetidus flower. In seed plants, the ovule is the structure that gives rise to and contains the female reproductive cells. It consists of three parts: the integument, forming its outer layer, the nucellus (or remnant of the megasporangium), and the female gametophyte (formed from a haploid megaspore) in its center.
An important risk factor for placenta accreta is placenta previa in the presence of a uterine scar. Placenta previa is an independent risk factor for placenta accreta. Additional reported risk factors for placenta accreta include maternal age and multiparity, other prior uterine surgery, prior uterine curettage, uterine irradiation, endometrial ablation, Asherman syndrome, uterine leiomyomata ...
Decidualization is required in some mammalian species where embryo implantation and trophoblast cell invasion of the endometrium occurs, also known as hemochorial placentation. This allows maternal blood to come into direct contact with the fetal chorion, a membrane between the fetal and maternal tissues, and allows for nutrient and gas ...