Of what is the normal umbilical cord comprised?

Choice A rationale This configuration is known as a single umbilical artery (SUA), an anatomical variation or anomaly, not the normal composition. Normally, deoxygenated blood leaves the fetus via two arteries, and oxygenated blood returns via one vein. SUA is associated with a higher risk of fetal anomalies, including cardiac, renal, and skeletal defects, necessitating further diagnostic evaluation during pregnancy. The normal composition is two arteries and one vein. Choice B rationale The typical human umbilical cord contains only one umbilical vein, not two. This single vein is responsible for carrying oxygenated, nutrient-rich blood from the placenta to the fetal circulation. The presence of two veins is an extremely rare and abnormal variant, and it would deviate significantly from the normal physiological structure necessary for proper feto-placental gas and nutrient exchange. Choice C rationale The normal umbilical cord is comprised of two umbilical arteries and one umbilical vein, all encased in Wharton's jelly for protection. The two arteries carry deoxygenated blood and metabolic waste away from the fetus to the placenta, while the single vein carries oxygenated blood and nutrients to the fetus. This structure ensures efficient bidirectional transport for fetal survival. Choice D rationale The normal complement of vessels is two arteries carrying blood away from the fetus and one vein carrying blood to the fetus. This choice reverses the normal number and directionality of blood flow for the vein. The vein is singular and carries blood to the fetus, while the arteries are paired and carry blood away from the fetus.