Read from Dr. Chen Yu Sui’s notes

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Umbilical cord

  • 2 arteries & veins entwined
    • surrounded by mucopolysaccharide substance
      • Wharton’s Jelly

Amnion

  • Fused with chorion at end of 2nd month
  • No blood & nerve supply

Chorion

  • Inner aspect: in contact with amnion
  • Outer ascpect: in contact with maternal decidua
  • No blood & nerve supply
  • Cotyledon (lobule)
    • forms a unit which contains a main chorionic villous tree

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Decidua basalis

  • non glandular, non vascular cells of the endometrial CT
  • produced by steroid-dependent division & differentiation of maternal uterine stromal cells

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Placentral functions

 Maintenance of pregnancy

  • Human Placental hCH
    • acts on corpus luteum
      • prevent luteolysis
      • stimulate progesterone production
    • acts on placenta
      • enhance conversion of maternal LDL cholesterol to pregnenolone & progesterone
    • Regulate development of foetal adrenal & gonad
      • during 1st trimester
    • Suppression of maternal immune system
      • prevent rejection of fetus
    • As tumour marker
  • Plactental Lactogen (hPL)/ chorionic somatomammotropin (hCS)
    • Similar features to GH & prolactin
    • alter maternal glucose metabolism & lipolysis
    • Causes hyperinsulinemia due to glucose load
      • stimulate insulin secretion
      • prolonged hyperinsulinemia
        • peripheral insulin receptor resistance
      • decrease glucose utilisation
        • diverts glucose to fetus
  • Placental progesterone
    • Independent of factors
      • not influenced by pituitary hormones
    • increased when placental hCG drops
    • blockade of myometrial prostaglandins production
      • reduce uterine contractility
    • stimulate endometrial gland secretion
    • Inhibit ovulation
      • prevent FSH secretion
    • Immunosuppressant
      • inhibit fetal rejection
  • Placental oestrodiol
    • DHEA-sulphate from foetal adrenal gland
      • human placenta does not have 17-alpha hydroxylase
      • converted to DHEA by placental sulfatase
    • Growth of myometrial smooth muscles

Nutrient transport

  • Placenta act as surrogate
    • lung
    • gut
    • kidney
  • Nutrients cross interhaemal barrier by 3 mechanisms:
    • Passive/simple diffusion
      • lipid soluble molecules
        • O2, CO2
        • urea
        • fatty acids
        • drugs (aspirin)
    • Facilitated diffusion
      • hydrophilic solutes
        • D-glucose
        • lactate
    • Active transport
      • amino acids
      • Ca
      • Mg
      • Iodide
      • Iron
      • PO4
      • Vit A & C

Factors affecting rate of diffusion:

  • blood flow rates
  • foetal villous exchange total surface area
  • distance of diffusion
    • syncytial trophoblast
    • capillary endothelium
  • concentration gradient

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Placental Insufficiency

May result from

  • Umbilical-placental vascular anomalies
  • Multiple gestation
  • Placental thrombosis, infection, infaction, abruption
  • Placentral previa (at lower segment of uterus, cover cervix)
  • Cigarette smoking
    • inhibit amino acid transport across the placenta

Compromises nutrient transport and may cause intrauterine growth retardation (IUGR)

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Gestational trophoblastic diseases

Constitutes a spectrum of tumours & tumour-like conditions, characterised by proliferation of pregnancy-associated trophoblast tissue of progressive malignant potential.

There are 3 types:

  • Hydatidiform mole (complete mole)
    • normal karyotype (46 XX/XY)
    • all villi oedematous
    • diffuse, circumferential trophoblast proliferation
    • elevated hCG
    • Absent foetal parts
    • 2% choriocarcinoma
    • Rapid uterine enlargement
    • abnormal uterine bleeding in early pregnancy
      • passage of thin, watery fluid & bits of tissue
    • diagnosis by ultrasound
    • treatment:
      • mole removed by curettage
      • hysterectomy
  • Partial mole
    • Karyotype triploid (69 XXY/XXX)
    • Some villi oedematous
    • focal slight trophoblast proliferation
    • less elevated hCG
    • foetal parts present
    • choriocarcinoma rare
  • Invasive mole
    • mole penetrates & perforate the uterine wall
    • invasion of myometrium by hydropic chorionic villi
      • proliferation of cytotrophoblast & syncytiotrophoblast
      • hydropic may embolise to distant sites (but dont grow)
      • benign
      • rupture of uterus –> hemorrhage
  • Choriocarcinoma
    • epithelial malignant neoplasm of trophoblastic cell
      • from pregnancy/abortion
    • No chorionic villi
    • Abnormal proliferation of cytotrophoblast & syncytiotrophoblast
    • Invade myometrium
      • penetrate blood vessels & lymphatics
      • hemorrhage, ischaemic necrosis
    • metastasize
    • Clincal features:
      • irregular spotting of bloody brown
      • foul smelling fluid in the course of pregnancy, abortion or curettage
      • hCG elevated (higher than moles)
      • Gestational choriocarcinoma has better prognosis
        • non gestational choriocarcinoma more resistant to therapy

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