Question

how the blood form in body

Answer 1

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. The lymphatic tissues, particularly the thymus, the spleen, and the lymph nodes, produce the lymphocytes (comprising 20–30 percent of the white cells).

Answer 2

When the oxygen content of body tissues is low or the number of red blood cells decreases, the kidneys produce and release erythropoietin , a hormone that simulates the bone marrow to produce more red blood cells.The bone marrow produces and releases more white blood cells in responce to infections.