Hematopoiesis or hemopoiesis is the process of blood cell formation from undifferentiated stem cells committed to produce blood cells. In adults, this process occurs in the hematopoietic bone marrow. Remember that a large part of the adult bone marrow is occupied by white adipose tissue.
Each type of blood cell has its own lineage of differentiation: erythrocytic, granulocytic, monocytic, and lymphocytic lineage. The precursor cells of each lineage undergo mitosis and gradually differentiate into mature cells. These are then released into the bloodstream.
In addition, there is the process of production of platelets, which are fragments of cytoplasm cytoplasm that detach from very large cells called megakaryocytes.
Bone marrow cell smears
One way to study the cells involved in hematopoiesis is to analyze bone marrow smears. Bone marrow can be obtained by puncturing the medullary canal of bones, and the cells are spread on the surface of a histological slide and stained like blood smears. In adults, hematopoiesis is restricted to certain bones, for example, the iliac crest, ribs, and vertebrae.
By studying the smears, it is possible to follow the differentiation of cells in each lineage. In this module, the main stages of formation in the erythrocytic and granulocytic lineages will be analyzed.
Initially, recognizing the different stages of the various lineages may seem difficult, but if we know what happens during the differentiation of the various lineages, the study is greatly facilitated. This will be analyzed on the next page.
Cells in different stages of differentiation to matures cells of the various lineages are present in the smears. Since bone marrow tissue is obtained by puncture, peripheral blood cells are always present in small amounts in the smears.
Remember that with routine staining, basophilic means a structure that stains blue, eosinophilic refers to a cellular component that stains pink or orange, and metachromatic refers to structures stained purple.