Hematopoiesis and Immune System Development

Haematopoiesis is the fusion and development of blood cells that occurs during embryonic development and continues into maturity to generate and replenish the blood system. Cellular blood components are produced by hematopoietic stem cells, which are found largely in the bone marrow, a key site of adult haematopoiesis. The blood system includes more than ten different blood cell types with numerous functions.

Functions: Leukocytes represent many specialized cell types involved in innate and acquired immunity. Erythrocytes deliver O2 and CO2 transport, whereas megakaryocytes create platelets for blood clotting and wound healing.

• Synthesis and development of blood cell
• Leukocytes and erythrocytes
• Development B-cells and T-cells

Synthesis and development of blood cell:
Blood has been described as the "river of life," as it transports numerous substances to various parts of the body. Red blood cells are an important part of the blood. Their job is to carry oxygen to the body's tissues in exchange for carbon dioxide, which they take to the lungs to exhale. The red bone marrow of bones is where red blood cells are formed. Hemocytoblasts are stem cells found in red bone marrow.They are responsible for the formation of all of the components found in blood.

If a stem cell decides to grow into a proerythroblast, it will develop into a new red blood cell. A red blood cell takes roughly two days to develop. Every second, the body produces around two million red blood cells.Blood has both cellular and liquid components. When a blood sample is spun in a centrifuge, the formed elements and fluid matrix of blood can be separated. Blood is made up of around 45% red blood cells, fewer than 1% white blood cells and platelets, and 55% plasma.

Leukocytes and erythrocytes:
RBCs are red because of the presence of haemoglobin, an iron-rich protein that binds with oxygen to produce the colour. Because of its high concentration in the blood, RBC gives it a red colour. Red blood cells, also known as erythrocytes, are round, tiny, and biconcave in shape, but due to their flexibility, they seem bell-shaped while passing through narrow channels. They transport oxygen to the body's tissues. It is critical to have an iron and vitamin-rich diet in order to maintain a healthy RBC count in the body. Anemia is caused by a low RBC count, and frequent symptoms include irregular heartbeat, pale complexion, feeling chilly, weariness, and joint discomfort.

Red blood cells' major role is to carry oxygen from the lungs to tissue in various sections of the body via the blood circulation system. They also carry carbon dioxide back to the lungs, where it is expelled from the body. Because of its bi-concave form, the RBC aids in the exchange of oxygen at a constant rate and over a large surface.

Because they lack haemoglobin, white blood cells are colourless. White blood cells, also known as leukocytes, protect the body from infections by creating antibodies that strengthen the body's defence system against germs and viruses. The circulatory system utilized by these cells is another essential element that helps us distinguish between RBC and WBC. WBC circulates via the circulatory system and is also found in the lymphatic system. Only the cardiovascular circulatory system is used by red blood cells. These cells attack invading bacteria, viruses, and germs, assisting in the fight against infection.

Development B-cells and T-cells:
T and B lymphocytes (T and B Cells) are involved in the acquired or antigen-specific immune response because they are the only cells in the organism that can recognize and respond specifically to each antigenic epitope. B cells have the ability to transform into plasmacytes and are in charge of generating antibodies (Abs). Thus, humoral immunity is dependent on B cells, whereas cell immunity is dependent on T cells. The ontogeny processes for each kind of lymphocyte are covered, along with their basic features, the many subpopulations reported to date, the signalling pathways used for their activation, and their main functions based on the immunological profile that they present.