Elisabet O. Orville
Objectives The placenta which plays such a major role in pregnancy has a rather complicated structure and numerous functions. This lesson plan is a step-by-step approach to understanding this multifaceted organ.
Strategies:
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1. Show your students photos of the placenta from “A Child is Born” by Nilsson (pp 81, 128-9) and Beaconsfield, 1980, (pp 94, 98).
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2. Draw a circle on the board twenty centimeters in diameter with the cord attached to the center to represent a life size placenta. Ask your class to figure how much it weighs if its ratio to an eight pound baby is 1:6.
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3. Make copies of the diagram on the next page called “Gross section of the Placenta” for each student. Discuss how the maternal side is different from the fetal side. Then have them color in the blood vessels (red for oxygenated blood and blue for deoxygenated). There is a transparency at the Teachers Institute which you can use as a guide.
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4. Emphasize that the fetal villi which contain thin-walled capillaries are bathed in maternal blood, and that this is where all exchanges of materials take place.
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5. There are three empty boxes on the diagram of the placenta marked: FETUS SENDS TO MOTHER, MOTHER SENDS TO FETUS, PLACENTA MAKES THESE HORMONES. Use the information below and see a) if students can figure out which box each substance belongs in and b) what effect it could have on either fetus or mother.
For instance,
glucose
, is sent to fetus from mother and it supplies energy. (Don’t be too quick to give answers).
MOTHER SENDS TO FETUS
oxygen
water
glucose
fatty acids
amino acids
vitamins and iron
carbon monoxide
alcohol
heroin
nicotine
viruses (such as rubella & herpes
IgG antibodies which protect against some diseases.
PLACENTA MAKES THESE HORMONES
HCG (human chorionic gonadotropin)
HCS (human chorionic somatomammotropin)
progesterone
estrogen
FETUS SENDS TO MOTHER
carbon dioxide
urea and uric acid
bilirubin
heat
(figure available in print form)
CROSS section of the placenta
