The placenta is an organ that develops during pregnancy and is essential for the growth and development of the fetus. It forms from both maternal and fetal tissues and serves as a connection between the mother and the developing baby. Here's a description of its structure and functions:

Structure:
The placenta is a flat, circular organ that attaches to the uterine wall. It is composed of two main parts:

1. Maternal side: This side of the placenta is formed by the lining of the uterus. It contains maternal blood vessels that supply nutrients and oxygen to the developing fetus.

2. Fetal side: This side of the placenta is formed by the fetal chorion, a membrane that surrounds the developing fetus. It contains fetal blood vessels that bring nutrients and oxygen to the fetus and remove waste products.

Functions:
The placenta performs several important functions that are crucial for the well-being of the developing fetus:

1. Nutrient and gas exchange: The placenta acts as a barrier between the maternal and fetal circulatory systems, allowing for the exchange of nutrients, oxygen, and waste products. Oxygen and nutrients from the mother's bloodstream diffuse into the fetal blood vessels within the placenta, while waste products like carbon dioxide pass from the fetal blood into the maternal blood for elimination.

2. Hormone production: The placenta produces hormones that are necessary for maintaining pregnancy and supporting fetal development. These hormones include human chorionic gonadotropin (hCG), which helps sustain the pregnancy, and progesterone, which maintains the uterine lining and prevents contractions.

3. Immune protection: The placenta acts as a barrier against harmful substances and pathogens, preventing them from reaching the fetus. It also produces antibodies that provide passive immunity to the baby, helping protect against certain infections.

4. Waste elimination: The placenta eliminates waste products produced by the fetus, such as urea and uric acid, by transferring them into the maternal bloodstream for excretion.

5. Endocrine function: In addition to hormone production, the placenta also plays a role in regulating maternal metabolism and adapting the mother's body to support the growing fetus.

Overall, the placenta is a vital organ that ensures the exchange of nutrients, gases, and waste products between the mother and the developing baby. Its functions are critical for fetal growth and development, and any abnormalities or complications with the placenta can have significant implications for both the mother and the fetus.