The intervillous space of the placenta contains
**Core Concept**
The intervillous space of the placenta is a critical area for maternal-fetal exchange, where oxygen and nutrients are transferred to the fetus from the mother's bloodstream. This space is characterized by a rich network of fetal villi, which increase the surface area for exchange.
**Why the Correct Answer is Right**
The intervillous space contains maternal blood, which flows through this space and comes into close proximity with the fetal villi. This allows for the exchange of oxygen, nutrients, and waste products between the mother and the fetus. The maternal blood in the intervillous space is rich in oxygen and nutrients, which are then transferred to the fetus through the villi.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it does not accurately describe the contents of the intervillous space.
**Option B:** This option is incorrect because it is not a specific component of the intervillous space.
**Option C:** This option is incorrect because it is not a characteristic feature of the intervillous space.
**Clinical Pearl / High-Yield Fact**
The intervillous space is a critical area for maternal-fetal exchange, and any disruption to this space can have significant consequences for fetal development and well-being.
**Correct Answer: D. Maternal blood**