?How blood cells are produced

How blood cells are produced

　　Blood cell analyzer, blood cells are derived from bone marrow hematopoietic stem cells. In addition to their ability to proliferate, stem cells can migrate out of bone marrow hematopoietic tissues under certain circumstances. As blood flows to extramedullary tissues, hematopoietic cell nodules are formed, called colony forming units. Each nodule is composed of many differentiated cells of the same type. These cells are derived from the division and differentiation of a stem cell. Although stem cells have the ability to replicate and differentiate into various blood cells themselves, under normal circumstances, they are not in a proliferating state, but in the resting G0 phase.

The original stem cells of the hematology analyzer can be differentiated into two major branches: one is the colony forming unit cell (CFU-C), also known as bone marrow stem cells, which is a pluripotent system of red blood cells, neutrophils, eosinophils and platelets. stem cell. The colony-forming unit cells are mainly derived from bone marrow. Before developing into erythrocytes, granulocytes and megakaryocytes, they go through the directional stem cell stage of each line. The other is lymphoid stem cells, also known as lymphatic stem cells, which is the birthplace of higher animal immune system. The differentiation and development process are closely related to the stimulation of antigen. Lymphatic stem cells are also pluripotent stem cells, which can differentiate into two different types of directional stem cells. One is thymus-derived T lymphocytes or T cells, and the other is bone marrow-dependent B lymphocytes or B cells. These two cells are transformed into prolymphocytes and protoplasms after restimulation of the corresponding antigens, and then gradually Mature, called lymphocytes and plasma cells.

In short, blood cells are derived from the hematopoietic stem cells of the bone marrow. First, the pluripotent stem cells differentiate into colony forming unit cells (marrow stem cells) and lymphoid stem cells, and then the bone marrow stem cells differentiate into directional stem cells of various lines. After primitive and naive At other stages, development, proliferation and finally mature into red blood cells, granulocytes, monocytes and platelets. Lymphoid stem cells go through two stages of primitive and naive development, proliferation and maturation; under the stimulation of antigen, they are transformed into protolymph cells and protoplasm cells, respectively, and proliferate and mature into immunologically active lymphocytes and plasma cells.

　　The proliferation of blood cells is carried out by division, but only naive cells have the ability to divide, once they have matured to a certain stage. The proliferation stops. There are two general forms of cell division: (1) mitosis (indirect division) When cells divide, special filaments appear, so it is called mitosis. Mitosis is the main form of blood cell proliferation. There are no mitotic cells in the circulating blood of normal people. The number of mitotic cells in hematopoietic tissues reflects the degree and state of their proliferation. The Meilun split process can be divided into four phases, mainly manifested in nuclear changes. ① Early stage (also known as monofilament stage): when the cell begins to divide. The cell body becomes spherical, the nucleus is enlarged, the nuclear chromatin is aggregated into a single columnar chromosome, and the nuclear membrane and nucleosome disappear, like a silk ball. Cytoplasmic staining became lighter, organelles and inclusions were temporarily concealed, and centrosomes showed. ②Mid-term (also known as single stellate phase): The central body begins to split, gradually toward the poles, and there is a filamentous body in between, shaped like a spindle, called the spindle body. The nuclear chromosomes are arranged in the middle of the spindle, like a star or a chrysanthemum. ③Late stage (also known as double star stage): each chromosome splits into two evenly, and the filaments contract, so that the split chromosomes follow the centrosome toward the two ends of the cell and are arranged into two star shapes. The cytoplasm begins to contract. ④Late stage (also known as spheroid phase): Chromosomes tending to gather at both ends of the cell begin to gather into a spheroid shape, and then disperse into chromatin, forming small nuclei of two new nuclei. At this time, the cytoplasm can form a dumbbell shape, and finally the cytoplasm separates , The cell divides into two.

(2) Amitosis (direct division) The manifestation of the division process is relatively simple, usually the nucleosome of the cell first begins to separate, then the surface of the nucleus shrinks, and then gradually deepens and decomposes into two, followed by the cytoplasm Separated to form 2 daughter cells directly.