## **Core Concept**
The umbilical cord is a vital structure that connects the fetus to the placenta, playing a crucial role in fetal development by facilitating the exchange of oxygen, nutrients, and waste products. It contains two umbilical arteries and one umbilical vein, which are responsible for this exchange. The umbilical cord is composed of **Wharton's jelly**, a gelatinous substance that protects the blood vessels.

## **Why the Correct Answer is Right**
The correct answer, **D. Contains two umbilical arteries and one umbilical vein**, is accurate because the umbilical cord typically contains two arteries and one vein. The two umbilical arteries carry deoxygenated blood from the fetus to the placenta, while the single umbilical vein carries oxygenated blood and nutrients from the placenta to the fetus. This arrangement is crucial for the proper exchange of substances and for maintaining fetal health.

## **Why Each Wrong Option is Incorrect**
- **Option A:** This option is not provided, but any statement contradicting the known anatomy or function of the umbilical cord would be incorrect.
- **Option B:** Similarly, without the specific content of Option B, we can infer that any statement not aligning with established facts about the umbilical cord (e.g., suggesting it contains more or fewer vessels than correct) would be incorrect.
- **Option C:** Again, without specifics, any claim not supported by accurate anatomical or physiological information regarding the umbilical cord would be incorrect.

## **Clinical Pearl / High-Yield Fact**
A key point to remember is that the presence of **two umbilical arteries** is considered a normal finding, and their absence or presence of only one artery can be associated with fetal anomalies and increased risk of growth restriction. The umbilical cord usually inserts at the center of the placenta but can have **velamentous insertion** (into the membranes) or **marginal insertion** (at the edge of the placenta), which may pose risks.

## **Correct Answer:** D. Contains two umbilical arteries and one umbilical vein.