Embriology

Fetal Development and Placenta

• The placenta is responsible for the exchange of nutrients and gases between the mother and fetus.
• The heart begins to contract and push blood through the blood vessels around 3-4 weeks after fertilization.

Placenta Structure and Function

• The decidua basalis, the part of the placenta that originates from the endometrium, forms the maternal side of the placenta.
• The placenta is a flat, disk-shaped organ.
• The average weight of the placenta is around 500 grams.
• The average thickness of the placenta is around 2-3 cm.
• The placenta occupies around 30-40% of the inner surface of the uterus.
• The placenta plays a crucial role in establishing blood flow in the cardiovascular system by exchanging oxygen and nutrients from the mother's blood with waste products from the fetus.

Blood Flow and Circulation

• The primitive blood vessels in the cardiovascular system are responsible for the exchange of oxygen and nutrients between the mother and fetus.
• The umbilical cord, which is around 50-60 cm in length, connects the fetus to the placenta and allows for the exchange of oxygen and nutrients.

Amniotic Fluid and Membranes

• The amnionic fluid is a clear, pale yellow liquid that surrounds the fetus and is composed of 98-99% water, proteins, and other substances.
• The syncytiotrophoblasts produce human chorionic gonadotropin (hCG).
• The amnion is the innermost membrane that surrounds the fetus and amniotic fluid.
• Amniotic fluid is exchanged between the fetus and mother through the process of diffusion and active transport.
• The fetus swallows amniotic fluid, which is then absorbed into the bloodstream and excreted as urine.
• Oligohydramnios is a condition where there is too little amniotic fluid, while polyhydramnios is a condition where there is too much amniotic fluid.

Placenta Development and Function

• The chorionic villi are responsible for the exchange of oxygen and nutrients between the mother's blood and the fetus.
• The intervillous space is the area that contains the mother's blood in the placenta.
• The syncytiotrophoblast is a layer of cells that forms the outermost layer of the chorionic villi and is responsible for the exchange of oxygen and nutrients.
• The cytotrophoblast coat is a layer of cells that covers the chorionic villi and is responsible for the formation of the placenta.
• The umbilical arteries and veins are responsible for carrying oxygen-poor blood away from the fetus and oxygen-rich blood to the fetus, respectively.