BGDA Practical Placenta - Placental Functions

Term Placenta

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 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.

Placenta Measurements

Term Placenta Measurements

Morphometric indices at term of placental composition, villous capillarization and the mean cross-sectional areas of peripheral villi and capillaries.

Variable	Unit	Placenta
Intervillous space	mL	213
Stem villi	mL	71.4
Peripheral villi	mL	326
Trophoblast	mL	95.5
Stroma	mL	184
Fetal capillaries	mL	46.9
Non-parenchyma	mL	41.5
Peripheral villi	km	89.2
Fetal capillaries	km	310
TS area villi	µm2	3700
TS area capillary	µm2	150
Capillaries	mL mL-1	0.147
Length ratio	km km-1	3.6

Data from a study sample of 15 normal placenta, mean placental volume, 652 ml.

Measurement methodology

Microscopical fields on stained sections were selected by systematic uniform random sampling and analysed stereologically to estimate the volumes of placental compartments and total lengths of villi and fetal capillaries. Mean cross-sectional areas of peripheral villi and capillaries, together with measures of villous capillarization (capillary volume densities and capillary : villus length ratios), were derived from global volumes and lengths.

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.

<pubmed>21766440</pubmed> <pubmed>21789231</pubmed> <pubmed>19732616</pubmed>| PMC2767264

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