Placenta PDF

PLACENTA 1. Primary site of nutrient and gas exchange between the mother and fetus 2. Fetomaternal organ that has two components: ▪ A fetal part that develops from the part of the chorionic sac...

PLACENTA 1. Primary site of nutrient and gas exchange between the mother and fetus 2. Fetomaternal organ that has two components: ▪ A fetal part that develops from the part of the chorionic sac ▪ A maternal part that is derived from the endometrium (inner layer of uterine wall) 3. The placenta and umbilical cord function as a transport system for substances passing between the mother and the fetus 4. ▪ Nutrients and oxygen pass from the maternal blood through the placenta to the fetal blood ▪ Waste materials and carbon dioxide pass from the fetal blood through the placenta to the maternal blood Reference: Wheater’s Functional Histology-A Text & Colour Atlas By Young, 6th Edition Reference: Human Embryology and Developmental Biology, By Carlson, 3rd Edition i Circulation of amniotic fluid to and from the fetus Structure of placental villi What is the common thing between the placental membrane layers in early pregnancy, late pregnancy, and full term pregnancy? syncytiotrophoblast ‫قال دوروا على املتشابه في الثالث ساليدات‬ ‫هذي واتوقع ان قصده كذا بس مو متاكده فا‬ ‫ذاكروها كلها‬  TRANSFER ACROSS THE PLACENTAL MEMBRANE MNEMONIC DEVICE (GERMAN MADE) Immunoglobulins (Five types) IgG Reference : BRS Embryology, by Dudek, 6th edition IgM IgA IgD IgE Mercedes-Benz E-Class GAMED “MADE WILL NOT CROSS THE PLACENTAL MEMBRANE”  MULTIPLE PREGNANCY 2. MONOZYGOTIC TWINS (=IDENTICAL TWINS): Result from splitting of the zygote at various stages of development 2E. ▪ 65% of monozygotic twins: - Splitting of the zygote usually occurs at the early blastocyst stage - The inner cell mass splits into two separate groups of cells within the same blastocyst cavity - The two embryos have a common placenta, and a common chorionic cavity but separate amniotic cavities [The fetuses have ONE PLACENTA, ONE CHORION, and TWO AMNIOTIC SACS] Illustrations of how approximately 65% of monozygotic twins develop from one zygote by division of the inner cell mass - These twins always have separate amnions, a single chrionic sac, and a common placenta - If there is anastomosis of the placental vessels, one twin may receive most of the nutrition from the placenta Reference: Before we are Born- Essentials of Embryology and Birth Defects, By Moore, 8th Edition  MULTIPLE PREGNANCY 2. CONJOINT TWINS (=SIAMESE TWINS) Conjoint: Joined together 2I. Seen in monozygotic twins (Siamese: Connecting two or more pipes or hoses so as to permit discharge in a single stream) 2J. Embryonic disc does not completely split or divide ONE amnion; ONE chorion; ONE placenta Reference: Before we are Born- Essentials of Embryology and Birth Defects, By Moore, 8th Edition Diagrams illustrating how some monozygotic twins develop Division of the embryonic disc results in two embryos within one amniotic sac A. Complete division of the embryonic disc gives rise to twins B. Incomplete division of the disc results in various types of conjoined twins  TWIN TRANSFUSION SYNDROME (TWIN-TWIN TRANSFUSION SYNDROME-TTTS) 1. Occurs in 15% to 30% of monochorionic –diamniotic monozygotic twins 2. There is shunting of arterial blood from one twin through arteriovenous anastomoses into the venous circulation of the other twin 3. The donor twin is small, pale, and anemic whereas the recipient twin is large and polycythemic 4. The placenta shows similar abnormalities: [Donor twin: Oligohydramnios; Recipient twin: Polyhydramnios] The part of the placenta supplying the anemic twin is pale, whereas the part supplying the polycythemic twin is dark red 5. In lethal cases, death results from anemia in the donor twin and congestive heart failure in the recipient twin Reference: Medical Embryology By Langman, 13th Edition Illustrations of how approximately 65% of monozygotic twins develop Monozygotic twins with twin transfusion syndrome from one zygote by division of the inner cell mass Placental vascular anastomosis produced unbalanced - If there is anastomosis of the placental vessels, one twin may receive most of the nutrition from the placenta blood flow to the two fetuses Reference: Before we are Born- Essentials of Embryology and Birth Defects, By Moore, 8th Edition THANKS