Question

Where BLood formation occurs in human beings?​

Answer 1

Blood cells do not originate in the bloodstream itself but in specific blood-forming organs, notably the marrow of certain bones. In the human adult, the bone marrow produces all of the red blood cells, 60–70 percent of the white cells (i.e., the granulocytes), and all of the platelets.

Answer 2

All of the blood cells arises from your bone marrow, primarily of the long bones in the arms, legs, back and sternum.
The process of making blood cells is called hematopoiesis.