Simple, easy to follow, basic concepts for undergraduates

1. Placental
Development
( for undergraduates)
Sona P.S.
Assistant Professor,
Govt. College of Nursing , Trivandrum

2. Placental Development
• 3 weeks after fertilisation -Small projections appear on
the trophoblastic layer of the blastocyst , proliferate to
form chorionic villi
• Abundant in decidua basalis called chorionic frontosum &
develops into placenta
• The villi under decidua capsularis are less abundant and
atrophy to form chorionic leave which later form chorion

3. Placental Development
• Chorionic villi erode the walls of maternal blood vessels
and opens up to form a pool of maternal blood(sinuses)
• Few villi attach deeply into decidua(anchoring villi)
• Placental circulation establishes by 17th day
• Placenta completely develops and functions by 10th week
after gestation

4. Placenta – Structure

6. Cotyledon of Placenta
• Each villus and its branches form the
cotyledon
• 15-30 lobes(average 20)

8. •Discoid shape
•Average weight 500 gm (200 – 800 gm)
•1/6 of baby’s weight at term
•Average diameter 20 cm and thickness 2.5 cm
•Maternal and fetal surfaces
•Maternal surface rough and granular
•Fetal surface smooth, shiny and transparent
•Umbilical cord- attached to fetal surface
Mature Placenta

10. Functions of placenta
• Respiration
• Nutrition
• Storage –stores vitamins, iron and glucose
• Excretion – CO2, bilirubin from RBC, urea and uric acid
• Protection – barrier function, transfer antibodies, shock absorber
for the fetus
• Endocrine-hCG, progesterone, HPL

11. Mechanism of Transfer
• Diffusion – water, oxygen, CO2, urea and simple amines
• Active transport –transfer of Iron and ascorbic acid from mother
• Phagocytosis by chorionic villi- immunoglobulins