HEMATOPOIESIS

We all know that when pathogens enter our body, they get absorbed in the blood vessels. Our body has a well-connected network of blood vessels and these blood vessels contain blood which contains cells and plasma. There are about ten different types of cells in the blood vessels which can be classified into three groups as shown in Red Blood Cells, White blood cells. T and B Lymphocytes, natural killer cells, monocytes, neutrophils, eosinophils, basophils) and platelets. White blood cells are the cells that protect our body from pathogens.

Red blood cells, white blood cells, and platelets are produced in the bone marrow and have a common precursor: a hematopoietic stem cell. Stem cells have a characteristic ability to divide asymmetrically i.e., one daughter cell continues to be a stem cell of the identical type, and at the same time, the other daughter cell acquires a new identity. In the case of hematopoietic stem cells, which are found in the bone marrow, one daughter cell remains a hematopoietic stem cell, while the other goes on to become a different type of stem cell: either a myeloid stem cell or a lymphoid stem cell.

The myeloid stem cells and lymphoid stem cells also divide asymmetrically, with their non-stem cell daughters generating the mature cell types of the blood. Myeloid stem cells give rise to red blood cells, platelets, and some types of white blood cells, while lymphoid stem cells give rise to the types of white blood cells classified as lymphocytes. Hematopoietic, myeloid, and lymphoid stem cells divide throughout a person's lifetime, generating new blood cells to replace old and worn-out ones.