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ANAT 1502 Embryo FINAL Review (Dr. Cane) (IMPORTANT!!)

ANAT 1502 Embryo FINAL Review (Dr. Cane) (IMPORTANT!!) -...

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Chapter 8: The placenta and fetal membrane · Introduction o Fetal part of placenta and fetal membranes separate fetus from Endometrium o Interchange of substances between maternal and fetal blood through the placenta o Vessels in umbilical cord connect placental circulation with the fetal circulation o Fetal membranes: chorion, amnion, yolk sac and allantois Develop from the zygote but do not participate in formation of fetus, except for yolk sac and allantois · The Placenta o A fetomaternal organ that has two components Fetal part: develops from part of chorionic sac Maternal part: develops from Endometrium o Placenta ad umbilical cord function as a transport system o Placenta and fetal membranes functions and activities: Protection Nutrition Respiration Excretion Hormone production Expelled afterbirth o Decidua Functional layer of Endometrium in a pregnant woman Has 3 regions · Decidua basalis: deep to conceptus that forms the maternal part of the placenta · Decidua capsularis: superficial part of the deciduas overlying the conceptus · Decidua parietalis: all remaining parts of decidua Decidua cells enlarge as glycogen and lipid accumulate in their cytoplasm Many of these cells degenerate in chorionic sac Provide a rich source of nutrition for the embryo o Development of placenta Characterized by rapid growth of trophoblast and development of chorionic sac and chorionic villi Chorionic villi cover entire chorionic sac until beginning of 8 th week As villi degenerate it produces the Smooth Chorion Villous chorion: bushy part of the chorionic sac, forms fetal part of placenta Maternal part of placenta formed by decidua basalis o Fetomaternal Junction Fetal part of the placenta attached to the maternal part of the placenta by the cytotrophoblastic shell Chorionic villi attached firmly to the decidua basalis anchor the chorionic sac to the decidua basalis Shape of placenta determined by the shape of the persistent area of chorionic villi Decidual tissue is eroded to enlarge the intervillous space The erosion produces several wedge-shaped areas of decidua – placental septa – projects toward the chorionic plate Placental septa divide the fetal part of placenta into irregular convex areas called cotyledons o Intervillous space Contains maternal blood derived from lacunae that developed in syncytiotrophoblast Results from coalescence and enlargement of lacunar networks Divided into compartments by the placental septa Free communication occurs between compartments because the septa do not reach the chorionic plate Maternal blood enters this space from spiral arteries in decidua basalis: drained by endometrial veins o Amniochorionic membrane Form by fusion of amnion and smooth chorion Ruptures during labor
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Preterm rupture of this membrane is the most common event leading to premature labor o Placental circulation
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