Lecture 33 - Fetal and Placental

Lecture 33 - Fetal and Placental - Lecture 33 Fetal and...

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Lecture 33 – Fetal and Placental Implantation Blastocyst Comes down fallopian tube uterus next to the deciduas and develop there where embryonic core is at Outer layer (trophectoderm) Placenta Chorion Inner cell mass Fetus Amnion Vascular circuit Endometrium Decidua of pregnancy Venous circulation Established day 8 to 10 (villi connect to maternal veins) Trophoblast Differentiation Cytotrophoblast Mononuclear Regenerative Structural, adhesive and invasive Chorionic villi, basal plate, extravillous, invasive, amnion - These cells can break off and those trophoblastic cells can break off and go into the maternal deciduas and they can get to the mother’s circulation/blood supply Syncytiotrophoblast Multinuclear cell mass Endocrine function Lines lacunar blood spaces Exchange barrier of placenta Touches maternal blood exchange barrier Microstructure of Syncytium - It has villous to maximize surface area allow for greater gas and liqid exchange Microvillous membrane Area 90 m 2 Deportation to mother Can break off and can be trapped by the liver and lungs (dangerous!) through the vena cava Transport barrier Oxygen molecule must go out of RBC, diffuse through plasma, and through the five layers above Microvillous membrane Syncytiotrophoblast cell Basal membrane Villous mesenchyme Fetal capillary endothelium Mature Placenta Umbilical cord 2 arteries, 1 vein Chorionic plate Villous trees Stem villi Anchoring villi Septae 15-20 lobes Intervillous space Maternal blood Maternal Vascular Connection Hypoxia of implantation Low P a O 2 before 10 weeks’ Stimulates trophoblast proliferation Vasculogenesis, angiogenesis Protects from oxidative damage **need low oxygen to grow since fetus getting oxygen through diffusion in the beginning (b/c a low oxygen tension is require for proliferation of the trophoblasts, this is protective from oxidative damage) Invasive cytotrophoblast (the ones that leave) Express integrins and proteases Plug maternal capillaries (keeps the oxygenated blood coming into the placenta) Establish arterial connection at 10 weeks Via endovascular invasion and remodeling Where the placenta grows into artery!??!?!... Second wave of invasion at 18-22 weeks Endothelial phenotype “pseudovascularization” of invasive trophoblast - Oxygenated blood can come in and the pO2 rises dramatically! **endocascular remodeling: trophoblasts can travel through the deciduas, replace the mother’s endothelium to force the artery to stay open and not be sensitive to vasopressors spiral arterioles Placental functions Gas exchange Nutrient delivery Waste removal Endocrine organ Immunologic barrier Controls parturition and…
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Placental growth decrease growth but villous volume increases throughout gestation Villous maturation
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