All the Circulating Red Blood Cells in an Adult Originate

Question

All the circulating red blood cells in an adult originate in the
A) heart.
B) thymus.
C) spleen.
D) red bone marrow.
E) lymph tissue.

Accepted Answer

Red blood cells, or erythrocytes, are produced in the red bone marrow of bones such as the sternum, ribs, and pelvis.