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The Placenta <ul><li>Early gestation (10-12 weeks) is the period of placentiation </li></ul><ul><ul><li>Fetus is nourished...
Placental Architecture <ul><li>Maternal and fetal blood do not mix:  “placental barrier” </li></ul><ul><ul><li>Fetal blood...
Figure 29.6  A Three-Dimensional View of Placental Structure Figure 29.6a
<ul><li>Chorionic villi extend into maternal tissue </li></ul><ul><ul><li>Forms intricate branching network for maternal b...
Placental Capacity Increases During Gestation <ul><li>Expression of transporters increases </li></ul><ul><li>The “brush bo...
Mechanisms of Nutrient Transfer Across the Placenta
Maternal to Infant Nutrient Transportation Across The Placenta
Fetal to Maternal Transport <ul><li>Carbon dioxide </li></ul><ul><li>Water & urea </li></ul><ul><li>Hormones </li></ul>
 
Factors Affecting Placental Transfer <ul><li>Placental size </li></ul><ul><li>Diffusion distance –  </li></ul><ul><ul><li>...
Factors Affecting Placental Transfer (cont) <ul><li>Maternal-placental metabolism of the substance </li></ul><ul><li>Disor...
<ul><li>Trophoblast secretes hormones to maintain pregnancy </li></ul><ul><ul><li>HCG </li></ul></ul><ul><ul><li>Estrogens...
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Placenta

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Transcript of "Placenta"

  1. 1. The Placenta <ul><li>Early gestation (10-12 weeks) is the period of placentiation </li></ul><ul><ul><li>Fetus is nourished by secretions of uterine endometrial glands in early gestation </li></ul></ul><ul><li>Placenta is a metabolically active tissue </li></ul><ul><ul><li>Responsible for exchange of nutrients, gases & metabolic waste products between maternal and fetal circulation </li></ul></ul><ul><ul><li>Glucose is predominant energy source for both placenta and fetus </li></ul></ul>
  2. 2. Placental Architecture <ul><li>Maternal and fetal blood do not mix: “placental barrier” </li></ul><ul><ul><li>Fetal blood flows through capillary networks within highly branched terminal chorionic villi </li></ul></ul><ul><ul><li>Maternal blood flows through intervillous space </li></ul></ul><ul><ul><ul><li>Uterine arteriols bring blood in </li></ul></ul></ul><ul><ul><ul><li>Uterine venules drain blood </li></ul></ul></ul>
  3. 3. Figure 29.6 A Three-Dimensional View of Placental Structure Figure 29.6a
  4. 4. <ul><li>Chorionic villi extend into maternal tissue </li></ul><ul><ul><li>Forms intricate branching network for maternal blood </li></ul></ul><ul><li>Umbilical cord connects fetus to placenta </li></ul>Placentation
  5. 5. Placental Capacity Increases During Gestation <ul><li>Expression of transporters increases </li></ul><ul><li>The “brush border” microvilli develop to: </li></ul><ul><ul><li>increase surface area </li></ul></ul><ul><ul><li>impede maternal blood flow </li></ul></ul><ul><li>Flow through the placenta at term is 500 ml/minute </li></ul>
  6. 6. Mechanisms of Nutrient Transfer Across the Placenta
  7. 7. Maternal to Infant Nutrient Transportation Across The Placenta
  8. 8. Fetal to Maternal Transport <ul><li>Carbon dioxide </li></ul><ul><li>Water & urea </li></ul><ul><li>Hormones </li></ul>
  9. 10. Factors Affecting Placental Transfer <ul><li>Placental size </li></ul><ul><li>Diffusion distance – </li></ul><ul><ul><li>diabetes and infection cause edema of the villi </li></ul></ul><ul><ul><li>distance decreases as pregnancy progresses and fetal needs increase </li></ul></ul><ul><li>Maternal-placental blood flow </li></ul><ul><li>Blood saturation with gases and nutrients </li></ul>
  10. 11. Factors Affecting Placental Transfer (cont) <ul><li>Maternal-placental metabolism of the substance </li></ul><ul><li>Disorders in expression or activity of nutrient transporters </li></ul><ul><li>Maternal use of tobacco, cocaine, alcohol </li></ul>
  11. 12. <ul><li>Trophoblast secretes hormones to maintain pregnancy </li></ul><ul><ul><li>HCG </li></ul></ul><ul><ul><li>Estrogens </li></ul></ul><ul><ul><li>Progesterone </li></ul></ul><ul><ul><li>hPL </li></ul></ul><ul><ul><li>Placental prolactin </li></ul></ul><ul><ul><li>relaxin </li></ul></ul>Hormones of the placenta
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