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Placenta

Placenta. By Joshua Bower Peer Support 2013/2014 J.Bower@warwick.ac.uk. Learning Outcomes. Placenta Understand how the placenta forms and grows Know how the structure of the placenta is linked to its functions Know in principle the main functions of the placenta

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Placenta

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  1. Placenta By Joshua Bower Peer Support 2013/2014 J.Bower@warwick.ac.uk

  2. Learning Outcomes • Placenta • Understand how the placenta forms and grows • Know how the structure of the placenta is linked to its functions • Know in principle the main functions of the placenta • Know in principle some of the main problems related to placental dysfunction • Pre-eclampsia • Relate maternal adaptations in pregnancy to some common complications of pregnancy including pre-eclampsia and gestational diabetes

  3. The embryo implants into the uterine endometrium around day 7.

  4. What are the THREE aims of implantation? [3] • Anchor the placenta • Establish the chorionic villus • Establish maternal/foetal blood flow within the placenta

  5. How does the chorionic villus adapt to meet the expanding need of the developing foetus? [3] • Thinning of placental barrier • Margination of foetal vessels • Massive expansion of surface area by arborisation

  6. There are 2 umbilical veins and 1 umbilical artery.

  7. Maternal-foetal blood flow is low pressure with a low flow rate.

  8. What are the THREE functions of the placenta? [3] • Endocrine (produce steroid and peptide hormones) • Transfer (nutrition, waste, gas exchange) • Immunity

  9. Which of the following is measured in a pregnancy test? LH Oestradiol FSH Testosterone hCG hPL

  10. hCG and hPL are peptide hormones

  11. When do (i) hCG and (ii) hPL levels peak? • (i) 10-12 weeks • (ii) Levels rise steadily during pregnancy

  12. What is the function of hCG, and why is this important? • hCG maintains the corpus luteum • The corpus luteum produces progesterone, which maintains a viable endometrium, until the placenta takes over

  13. Which molecule uses each transfer mechanism? H2O Glucose Immunoglobulins Amino acids Alcohol Passive diffusion Receptor-mediated pinocytosis Passive diffusion Facilitated diffusion Active transport

  14. IgM can cross the placental barrier It is IgG which can

  15. What effect does hCG have on maternal IgA, IgG and IgM? Why? Reduces levels Humoral immune depression to prevent rejection of the placenta by the mum, and vice versa Makes mother more susceptible to viruses

  16. Placenta Problems

  17. What term is used to denote a low-lying placenta? Placenta praevia

  18. A pregnant woman of 8 months presents with significant PV bleeding. What may have happened? Placental abruption

  19. What is placenta accreta, increta and percreta? • Uncontrolled invasion of the placenta … • Accreta – …into part of myometrium • Increta – …into whole myometrium • Percreta – …beyond myometrium into uterine serosa, and thus can atttach to the bladder or rectum

  20. What is post-partum haemorrhage, and what is the treatment? • Failure of the placenta and uterus to separate • The placenta maintains uterine blood supply, causing PV bleeding • Treatment – “extraction” of the placental tissue

  21. What is a malignant gestational trophoblastic tumour called? • Choriocarcinoma

  22. What is another name for a molar pregnancy? • Hydatidiform mole • Where a non-viable egg implants in the uterus • It is a gestational trophoblastic disease

  23. How can you differentiate a hydatidiform mole from an ectopic pregnancy? • Hydatidiform moles usually have high levels of hCG • In ectopic pregnancies, hCG levels are low

  24. What term describes when the placenta compensation cannot meet the needs of the foetus? • Intra-uterine growth restriction (IUGR)

  25. To finish…

  26. A pregnant lady presents to A+E with swollen hands and face. Examination reveals she is hypertensive with proteinuria. Diagnosis?

  27. What is pre-eclampsia? • Caused by abnormal placentation (development and arrangement of the placenta) or abnormal placental function • Proposed mechanism: • Reduced uterine-placental blood flow results in placental ischaemia, leading to release of factors causing endothelial dysfunction (e.g. TNF-alpha, IL-6), reduced NO and increased ROS • This in turn leads to altered renal function, increased TPR and ultimately hypertension

  28. What is eclampsia? • Acute and life-threatening tonic-clonic seizures in pregnancy

  29. What is placentophagia*? • * Won’t be examined** • ** …probably

  30. Questions? J.Bower@warwick.ac.uk

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