Why are the pulmonary arteries and umbilical called instead of blood vessels?

Pulmonary artery:

The name "pulmonary artery" specifically refers to the blood vessel that carries deoxygenated blood from the heart to the lungs for oxygenation. Unlike systemic arteries, pulmonary arteries do not supply oxygenated blood to other organs or tissues. Their primary function is to transport blood to the lungs, from where oxygenated blood is then carried back to the heart.

Umbilical cord and vessels:

The term "umbilical" refers to the connection between a developing fetus and its mother during pregnancy. The umbilical cord, which connects the fetus to the placenta, contains three blood vessels: two umbilical arteries and one umbilical vein. These blood vessels play crucial roles in the exchange of substances between the fetus and the maternal circulation.

- Umbilical arteries: The umbilical arteries carry deoxygenated blood and waste products from the fetus to the placenta. The waste products are then passed to the maternal circulation for elimination.

- Umbilical vein: The umbilical vein carries oxygenated blood and essential nutrients from the placenta to the fetus. This oxygen-rich blood supplies nourishment to the developing fetus.

Therefore, the pulmonary arteries and umbilical cord are referred to by these names to emphasize their specific functions in the circulatory system, highlighting the unique roles they play in transporting blood to and from the lungs in the case of pulmonary arteries and facilitating nutrient exchange between the mother and the fetus in the case of umbilical blood vessels.