Question

Progenitors formed in bone marrow but differentiating elsewhere are
(a) Pre N-K cells
(b) Pre-erythroblasts
(c) Pre-T Cells
(d) Myeloblasts

Answer 1

Hint: Bone marrow is a type of spongy tissue that mainly consists of stem cells. It also produces RBC, WBC and platelets. The progenitors which form inside the bone marrow get differentiated into the thymus.

Complete answer:
Bone marrow leads to the production of RBC, WBC and platelets. In WBC the lymphocytes form inside the bone marrow but get differentiated into the thymus. T cells determine the immune response to an antigen of the body. In the thymus, the T-cells differentiate into helper T- lymphocytes or cytotoxic T-cells which later form memory T-cells. Cytotoxic T-cells get activated by cytokines that kill and infect the cancer cells.

Additional Information:
Bone marrow is present inside the medullary cavity of the long bone, especially in the thigh bone. Bone marrow is of two types, one which is red bone marrow consisting of blood cells and the other is yellow bone marrow consisting of fat cells. Red Bone marrow consists of hematopoietic stem cells whereas yellow bone marrow consists of mesenchymal stem cells. The blood vessels inside the bone prevent immature blood cells from leaving the bone marrow and allow only mature blood cells to pass through the blood vessels. The difference between mature and immature blood cells is the presence of membrane protein.

So, the correct answer is Pre-T cells.

Note:
In a day bone marrow produces 200 million new blood cells with the addition of WBC and platelets. Each year in the US around more than 5,000 patients go through bone marrow transplantation due to various types of disease.