BGDA Practical Placenta - Placental Functions

Term Placenta

Increase in placental weight by birth gestational age GA.

Placenta Vasculature - MRI and CT

Term placenta viewed from the fetal side.

Magnetic Resonance Angiography (MRA)	Computed Tomography Angiography (CTA)
Legend CA - chorionic artery PSA - primary stem artery SSA - secondary stem artery TSA - tertiary stem artery

Exchange

• oxygen, carbon dioxide, carbon monoxide
• nutrients
  • water, glucose, vitamins
  • electrolytes
• waste products
  • urea, uric acid, bilirubin.
• hormones
  • mainly steroid, protein hormones poorly transported.
  • maternal thyroid hormone can slowly cross.
  • fetal insulin can impact on maternal diabetes.
• maternal antibodies
  • maternal IgG antibodies are transferred from about week 13 GA across the placenta
  • from the maternal lacunae syncytiotrophoblast cell endosomes bind IgG through neonatal Fc receptors.
• drugs and their metabolites
  • pre-existing maternal conditions
  • illegal drugs (fetal drug addiction)
• infectious agents
  • cytomegalovirus, rubella, measles, malaria, listeria, microorganisms

Endocrine

Protein and steroid hormones.

• Human chorionic gonadotrophin (hCG) - like leutenizing hormone, supports corpus luteum in ovary, pregnant state rather than menstrual, maternal urine in some pregnancy testing
• Human chorionic somatommotropin (hCS) - or placental lactogen stimulate (maternal) mammary development
  • rise through pregnancy, stimulates maternal metabolic processes, breast growth
• Human chorionic thyrotropin (hCT)
• Human chorionic corticotropin (hCACTH)
• Relaxin
• Steroid Hormones - progesterone (maintains pregnancy), estrogens (fetal adrenal/placenta)

Placental Estrogen

Fetal adrenal cortex produces dehydroepiandrosterone sulfate (DHEA-S) that is converted by the placenta into estrogens Placental estrogen, mainly estriol, suppresses gonadotropin secretion from the maternal pituitary gland. Maternal estrogen levels are often a useful indicator of fetal well being. Uterus - stimulates growth of the myometrium, antagonizes the myometrial-suppressing activity of progesterone. Mammary Gland - stimulates mammary gland ductal and alveolar growth. Fetal Ovary - stimulates development of female fetal ovary. A second role for fetal adrenal DHEA-S is possible regulation of the effects of glucocorticoids on the developing brain.

Placental Metabolism

Synthesises - glycogen, cholesterol, fatty acids

• provides nutrient and energy

Additional Information

Additional Information - Content shown under this heading is not part of the material covered in this class. It is provided for those students who would like to know about some concepts or current research in topics related to the current class page.

Drugs

Abnormal Development - Drugs

The placenta and fetal tissues may deal with drugs differently from adult target tissues. In particular, drugs are "cleared", metabolised and excreted, at a different rate in both the fetus and in newborn infants. In general there is a much lower rate of clearance.

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