What is the best description of the placenta's function?

The placenta serves as a critical organ during pregnancy, predominantly functioning as a transport system for nutrients and waste products between the mother and the developing fetus. One of its key roles is the transport of lipophilic substances, which are fat-soluble compounds. This is significant because lipophilic substances can cross the placental barrier more easily than hydrophilic ones, allowing for the exchange of essential nutrients and hormones necessary for fetal development.

Furthermore, the placenta not only supports metabolism and gas exchange but also plays a role in the secretion of hormones that are vital for maintaining pregnancy and supporting fetal growth. It is active in several physiological processes, rather than remaining passive, and while it does have some filtering capabilities, it is not designed as a comprehensive filter for toxins. It is essential to recognize that, while the placenta can provide some protection, it cannot completely filter out harmful substances.

In this context, the emphasis on its ability to transport lipophilic substances correctly encapsulates a primary function of the placenta in ensuring that the fetus receives adequate nutrition while also managing waste processes.