Vessels in umbilical cord:
**Core Concept**
The umbilical cord contains vessels that play a crucial role in fetal development, carrying oxygen and nutrients to the fetus and removing waste products. These vessels are **two umbilical arteries** and **one umbilical vein**. The **umbilical arteries** carry deoxygenated blood from the fetus to the placenta, while the **umbilical vein** carries oxygenated, nutrient-rich blood from the placenta to the fetus.
**Why the Correct Answer is Right**
The correct composition of the umbilical cord is essential for fetal survival. The **two umbilical arteries** are responsible for carrying waste and deoxygenated blood from the fetus to the placenta, where gas exchange occurs. The **one umbilical vein** then transports oxygenated, nutrient-rich blood back to the fetus. This arrangement ensures efficient exchange of gases and nutrients between the mother and the fetus.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it does not accurately represent the number and type of vessels in the umbilical cord.
**Option B:** This option is also incorrect as it misrepresents the composition of the umbilical cord.
**Option D:** Similarly, this option is incorrect and does not reflect the correct arrangement of vessels in the umbilical cord.
**Clinical Pearl / High-Yield Fact**
It's crucial to remember that the umbilical cord typically contains two arteries and one vein, which is essential for fetal development and survival. Any deviation from this normal anatomy can indicate potential fetal complications.
**Correct Answer:** D. Two arteries and one vein.