1. Placental Development
Definition:
The placenta is a temporary organ that develops during pregnancy to exchange nutrients, gases, and waste between the mother and fetus.
Formation of the Placenta:
- Develops from trophoblast cells of the blastocyst.
- Fully functional by 12 weeks of gestation.
Anatomy of the Placenta:
- Fetal Side: Covered by the amnion, contains umbilical cord.
- Maternal Side: Adheres to the uterus, composed of cotyledons (15–20 lobes).
2. Placental Circulation
Fetal Circulation (Umbilical Cord)
- Umbilical Arteries (2): Carry deoxygenated blood from fetus to placenta.
- Umbilical Vein (1): Carries oxygenated blood from placenta to fetus.
Maternal Circulation
- Uterine Arteries: Supply oxygenated blood to intervillous spaces of placenta.
- Uterine Veins: Drain deoxygenated blood back to the maternal circulation.
Mechanism of Exchange
- Oxygen, nutrients, and hormones diffuse from maternal blood to fetal blood.
- CO₂, urea, and waste products move from fetal blood to maternal blood for elimination.
3. Functions of the Placenta
1. Exchange of Gases & Nutrients
- Oxygen & Glucose → Transferred to fetus for growth.
- CO₂ & Waste Products → Removed via maternal circulation.
2. Hormone Production
- Human Chorionic Gonadotropin (hCG) → Maintains corpus luteum.
- Estrogen & Progesterone → Maintains pregnancy.
- Human Placental Lactogen (hPL) → Promotes fetal growth & maternal glucose metabolism.
3. Immune Protection
- Transfers maternal IgG antibodies → Provides passive immunity.
- Acts as a barrier against infections (Limited protection).
4. Waste Elimination
- Excretes fetal waste products (Urea, Bilirubin) into maternal circulation.
5. Protection Against Toxins
- Prevents some harmful substances from reaching fetus (But some drugs, alcohol, and viruses can cross).
4. Clinical Conditions Related to Placental Circulation
1. Placental Insufficiency
Causes:
- Preeclampsia, Hypertension, Diabetes, Smoking.
Effects: - Intrauterine Growth Restriction (IUGR), Fetal Hypoxia, Oligohydramnios.
2. Placenta Previa
Definition:
- Placenta implants over the cervical os, causing painless vaginal bleeding.
Management: - Avoid vaginal exams, C-section for delivery.
3. Placental Abruption
Definition:
- Premature separation of placenta from uterus, causing painful
vaginal bleeding.
Management: - Emergency C-section if fetal distress.
Summary Table: Placental Circulation & Functions
|
Feature |
Details |
|
Umbilical Arteries |
Carry deoxygenated blood from fetus to placenta |
|
Umbilical Vein |
Carries oxygenated blood to fetus |
|
Hormones Produced |
hCG, Estrogen, Progesterone, hPL |
|
Major Functions |
Gas exchange, Nutrient transfer, Immune protection,
Waste elimination |
|
Placental Abnormalities |
Placenta previa, Placental abruption, Insufficiency |
Key Takeaways
- Placenta develops by 12 weeks and supports the fetus until birth.
- Oxygen & nutrients flow from mother to fetus; CO₂ & waste return to the mother.
- Placental hormones regulate pregnancy (hCG, Estrogen, Progesterone).
- Placental insufficiency leads to IUGR & fetal distress.
