Final answer:
The placenta is a disk-shaped group of tissues where the small blood vessels from the mother and the offspring intertwine. It allows the exchange of substances between the maternal and fetal blood without mixing the blood. It is a temporary organ that forms from the trophoblast layer of cells after implantation.
Step-by-step explanation:
The placenta is a temporary organ that begins to form from the trophoblast layer of cells shortly after implantation. It is a disk-shaped group of tissues in which small blood vessels from the mother and the offspring intertwine but do not join. The maternal and fetal vessels are close together but separated by tiny spaces, allowing the exchange of substances across their capillary walls without the blood actually mixing.
The structure you are referring to is the placenta. The placenta is a disk-shaped organ that develops during pregnancy and provides a connection between the circulatory systems of the mother and the developing fetus. Small blood vessels from both the mother and the fetus intertwine within the placenta, allowing for the exchange of nutrients, oxygen, and waste products between the maternal and fetal bloodstreams. Importantly, the blood vessels do not physically join, ensuring a separation of the blood supplies while enabling the necessary exchange for the well-being and development of the fetus.