## **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 essential blood vessels that support fetal circulation. The composition and contents of the umbilical cord are critical for understanding fetal physiology.

## **Why the Correct Answer is Right**
The umbilical cord 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 vascular arrangement is essential for fetal circulation and gas exchange. The correct composition is therefore two arteries and one vein.

## **Why Each Wrong Option is Incorrect**
- **Option A:** This option is incorrect because it does not accurately represent the correct number and types of vessels found in the umbilical cord.
- **Option B:** This option is incorrect for similar reasons as Option A; it inaccurately describes the vascular composition of the umbilical cord.
- **Option C:** This option might suggest an incorrect arrangement or number of vessels, which does not align with the known anatomy of the umbilical cord.

## **Clinical Pearl / High-Yield Fact**
A key clinical pearl is that the absence of one umbilical artery (single umbilical artery) can be associated with fetal anomalies and increased risk of growth restriction. Therefore, identifying the normal vascular composition of the umbilical cord is crucial during prenatal ultrasound examinations.

## **Correct Answer:** C. Two arteries and one vein.