Fetal blood cells form hemoglobin-F, which has a higher affinity for oxygen than adult hemoglobin, hemoglobin-A, allowing _____. (Hemoglobin-F may hide defects in hemoglobin-A such as sickle cell anemia until several months after birth.)

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Anatomy refers to the internal and external structures of the body and their physical relationships, whereas physiology refers to the study of the functions of those structures.