Erythroblast Maturation and Its Role in Blood Cell Formation
Red blood cells (RBCs), also known as red cells, haematocytes, red blood corpuscles, erythrocytes or erythroid cells. The red blood cells are responsible for delivering oxygen to all the tissues of the body with the help of the circulatory system. The oxygen is taken up by RBCs and then discharged to various tissues of the body.
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Introduction to Haemoglobin
Iron is present in the haemoglobin. It can easily bind to oxygen. Haemoglobin helps in providing red colour to the red blood cells. Haemoglobin is responsible for helping the cell maintain deformability. It also helps in providing stability to the red blood cells when they travel through the circulatory system.
Human Red Blood Cells
The red blood cells of human beings are oval and biconcave in shape. No nucleus is present in them as they have to make up space for the haemoglobin. 2.4 million red blood cells are created in adults every second. The life span of red blood cells is around 100-120 days. After they die, they end up in the spleen which is known as the graveyard of RBC.
Life Cycle
Erythropoiesis is the process of the formation of red blood cells. The RBCs are matured in roughly 7 days. After that, they can live up to 120 days. In some chronic illnesses, the life span of RBCs is shortened.
Creation
In adult human beings, the red blood cells are created by the process of erythropoiesis. This process lasts for roughly 7 days. The life span of RBCs is around 120 days after that they are sent to the spleen which is the graveyard of RBCs. The RBCs are created in the bone marrow in adult human beings and in the foetal stage, they are created in the liver.
Senescence
The plasma membrane of an ageing red blood cell changes, rendering it vulnerable to macrophage detection and eventual phagocytosis throughout the mononuclear phagocyte system (liver, spleen, and lymph nodes), eliminating old and faulty cells and purifying the blood. Eryptosis, or the programmed death of red blood cells, is the name given to this process.
Clinical Significance
The following are examples of blood disorders that affect red blood cells:
Anaemias are disorders in which the blood's oxygen transport capacity is reduced due to decreased red cell count or a defect in the red blood cells or haemoglobin.
The anaemia caused by the deficiency of iron is the most prevalent one. It is caused when there is a deficiency of iron in the diet of an individual.
In sickle-cell anaemia disease, abnormally shaped red blood cells are formed. Instead of being an oval shape, the RBCs are sickle in shape. This causes a major problem in the passage of RBCs.
Transfusion
In blood transfusion, red blood cells are administered to the individual. The blood is checked continuously for diseases. Hepatitis B, Hepatitis C, and HIV are examples of all the different types of diseases that are present at the time of blood transfusion.
Conclusion
RBCs are also known as Red blood cells or red blood corpuscles. They are responsible for providing red colour to the blood. They lack a nucleus because their space for a nucleus is taken up by haemoglobin. Haemoglobin is responsible for carrying out the oxygen in the blood. Due to a deficiency of haemoglobin, anaemia can take place in the body. The graveyard of red blood cells is the spleen.
FAQs on Erythroblast: Definition, Stages, and Importance
1. What is an erythroblast and where is it primarily found in the body?
An erythroblast, also known as a normoblast, is an immature, nucleated red blood cell precursor. It is the cell responsible for synthesising haemoglobin. In a healthy individual, erythroblasts are found almost exclusively in the red bone marrow, which is the primary site of red blood cell production (erythropoiesis).
2. What are the key stages in the development of an erythroblast?
The maturation of an erythroblast from a stem cell into a red blood cell occurs in several distinct stages within the bone marrow. These stages are:
Proerythroblast: The earliest recognisable stage, a large cell with a prominent nucleus.
Basophilic Erythroblast: The cell begins actively synthesising haemoglobin, and its cytoplasm stains deep blue.
Polychromatophilic Erythroblast: Haemoglobin concentration increases, giving the cytoplasm a greyish-blue colour.
Orthochromatic Erythroblast: The cell is nearly filled with haemoglobin, and the nucleus becomes small and dense before being expelled.
Reticulocyte: The anucleated cell that leaves the bone marrow and matures into an erythrocyte in the bloodstream.
3. What is the main function of an erythroblast?
The primary function of an erythroblast is the synthesis of haemoglobin. Haemoglobin is the iron-containing protein molecule essential for transporting oxygen from the lungs to the rest of the body's tissues. The entire maturation process of an erythroblast is geared towards maximising haemoglobin production before it loses its nucleus to become a mature red blood cell.
4. How is an erythroblast different from a mature red blood cell (erythrocyte)?
The key differences between an erythroblast and an erythrocyte are:
Nucleus: An erythroblast possesses a nucleus, which is essential for directing haemoglobin synthesis. A mature erythrocyte is anucleated (lacks a nucleus).
Function: The erythroblast's function is production (synthesising haemoglobin). The erythrocyte's function is transportation (carrying oxygen).
Location: Erythroblasts are normally confined to the bone marrow, while erythrocytes circulate in the blood.
Size: Erythroblasts are generally larger than the compact, biconcave erythrocytes.
5. Why is the process of losing the nucleus so important for an erythroblast?
The expulsion of the nucleus (a process called enucleation) from the orthochromatic erythroblast is a critical step for two main reasons. First, it maximises the internal space of the cell for haemoglobin, thereby increasing its oxygen-carrying capacity. Second, the absence of a rigid nucleus allows the cell to adopt a flexible, biconcave disc shape, which enables it to deform and squeeze through the body's narrowest capillaries to deliver oxygen to tissues.
6. What is the importance of erythropoiesis for maintaining health?
Erythropoiesis, the process of producing red blood cells from erythroblasts, is vital for survival. Red blood cells have a limited lifespan of about 120 days. Erythropoiesis ensures a continuous and balanced replacement of old, worn-out RBCs. This constant replenishment maintains the blood's oxygen-carrying capacity, preventing conditions like anaemia and ensuring all body cells receive the oxygen needed for metabolism and function.
7. What does it mean if erythroblasts are found in a peripheral blood test?
The presence of erythroblasts in a peripheral blood smear is an abnormal finding. It indicates that the bone marrow is under extreme stress and is releasing immature red blood cells into circulation prematurely. This can be a sign of severe medical conditions such as massive blood loss, severe haemolytic anaemia (where RBCs are destroyed rapidly), hypoxia (low oxygen), or certain types of leukaemia and bone marrow disorders.
8. What is the role of the hormone erythropoietin (EPO) in relation to erythroblasts?
Erythropoietin (EPO) is a hormone, primarily produced by the kidneys, that acts as the main regulator of red blood cell production. When the body's oxygen levels are low, the kidneys secrete EPO into the bloodstream. EPO travels to the red bone marrow and stimulates the production and maturation of erythroblasts, thereby increasing the rate of erythropoiesis to restore normal oxygen levels.
9. How are erythroblasts connected to the medical condition erythroblastosis fetalis?
Erythroblastosis fetalis is a condition where a mother's antibodies attack the red blood cells of her foetus, causing severe anaemia. To compensate for the rapid destruction of mature RBCs, the foetal bone marrow works overtime and releases a large number of immature red blood cells, including erythroblasts, into the foetal circulation. The condition is named for this characteristic finding of excessive erythroblasts in the foetal blood.
