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Placental development

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Simple, easy to follow, basic concepts for undergraduates

Simple, easy to follow, basic concepts for undergraduates

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  • 1. Placental Development ( for undergraduates) Sona P.S. Assistant Professor, Govt. College of Nursing , Trivandrum
  • 2. Placental Development • 3 weeks after fertilisation -Small projections appear on the trophoblastic layer of the blastocyst , proliferate to form chorionic villi • Abundant in decidua basalis called chorionic frontosum & develops into placenta • The villi under decidua capsularis are less abundant and atrophy to form chorionic leave which later form chorion
  • 3. Placental Development • Chorionic villi erode the walls of maternal blood vessels and opens up to form a pool of maternal blood(sinuses) • Few villi attach deeply into decidua(anchoring villi) • Placental circulation establishes by 17th day • Placenta completely develops and functions by 10th week after gestation
  • 4. Placenta – Structure
  • 5. Cotyledon of Placenta • Each villus and its branches form the cotyledon • 15-30 lobes(average 20)
  • 6. •Discoid shape •Average weight 500 gm (200 – 800 gm) •1/6 of baby’s weight at term •Average diameter 20 cm and thickness 2.5 cm •Maternal and fetal surfaces •Maternal surface rough and granular •Fetal surface smooth, shiny and transparent •Umbilical cord- attached to fetal surface Mature Placenta
  • 7. Functions of placenta • Respiration • Nutrition • Storage –stores vitamins, iron and glucose • Excretion – CO2, bilirubin from RBC, urea and uric acid • Protection – barrier function, transfer antibodies, shock absorber for the fetus • Endocrine-hCG, progesterone, HPL
  • 8. Mechanism of Transfer • Diffusion – water, oxygen, CO2, urea and simple amines • Active transport –transfer of Iron and ascorbic acid from mother • Phagocytosis by chorionic villi- immunoglobulins