Question

Both RBC and WBC are formed in the
A. Thymus
B. Adrenal
C. Thyroid
D. Bone marrow

Answer 1

Blood cell formation, is additionally referred to as hematopoiesis or hemopoiesis. It’s the continuous process by which the cellular constituents of blood are replenished. Blood cells are divided into three groups: the red blood cells (erythrocytes), the white blood corpuscles (leukocytes), and also the blood platelets (thrombocytes).

Complete answer:
Blood cells don't originate within the bloodstream itself but in specific blood-forming organs, (the marrow of certain bones). Within the human adult, the bone marrow produces all of the red blood cells, 60–70 percent of the white cells, and platelets. The lymphatic tissues- thymus, spleen, and lymph nodes, produce the lymphocytes. The reticuloendothelial tissues of the spleen, liver, lymph nodes, and other organs produce the monocytes. The platelets, which are small cellular fragments instead of complete cells, are formed from bits of the cytoplasm of the large cells of the bone marrow.
Within the bone marrow, all blood cells originate from one form of unspecialized cell called a somatic cell. When a vegetative cell divides, it first becomes an immature red corpuscle, white vegetative cell, or platelet-producing cell. The immature cell then divides, matures further, and ultimately becomes a mature red somatic cell, white blood cell, or platelet.

In the human embryo, the primary site of blood formation is yolk sac. Later in embryonic life, the liver becomes the foremost important red blood cell-forming organ, but it's soon succeeded by the bone marrow, which in adult life is the only source of both red blood cells and also the granulocytes. Both the red and white blood cells arise through a series of complex, gradual, and successive transformations from primitive stem cells, which have the flexibility to make any of the precursors of a vegetative cell. Precursor cells are stem cells that have developed to the stage where they're committed to forming a specific quite new somatic cell.

Therefore, the correct option is D, bone marrow.

Note: The rate of blood corpuscle production is controlled by the body's needs. Normal blood cells last for a limited time and need to get replaced constantly. Certain conditions may trigger additional production of blood cells. When the oxygen content of body tissues is low or the quantity of red blood cells decreases, the kidneys produce and release erythropoietin, a hormone that stimulates the bone marrow to provide more red blood cells. The bone marrow produces and releases more white blood cells in response to infections. It produces and releases more platelets in response to bleeding.
Effects of aging on the blood: Aging has some effect on bone marrow and blood cells, leading to less cell-producing marrow. While this decrease generally doesn't cause problems, it's going to when the body experiences an increased demand for blood cells: the marrow of an older person is also less able to meet those increased demands.