Have you ever wondered if our bodies are constantly producing new blood? Yes, it is true. In medicine, this is what we call hematopoiesis. Simply put, this is the amazing process by which our bodies produce blood cells, or blood cells. Just like getting rid of an old car and buying a brand new one, our bodies are constantly removing old blood cells and making fresh, new blood cells in their place. This is how our bodies maintain a constant supply of blood. Isn’t it amazing? This process begins before we are even born and continues throughout our lives.
What is hematopoiesis? Simply put...
Okay, let's see what this word Hematopoiesis means. Although it may seem like a strange word, the meaning is very simple. This word comes from the combination of two words that come from the Greek language.
- 'Haîma' (Haima): This means 'blood' or ' blood '.
- Poesis (poesis): This means 'making something' or 'producing'.
Then when these two words are put together, the idea of
'blood formation' or
'blood production' comes up. It's very easy to understand, isn't it? Sometimes this process called
hematopoiesis is also called hemopoiesis, hematogenesis, or hemogenesis. All of these words mean the same thing.
What types of blood cells are produced by hematopoiesis?
Our blood is not made up of the same type of cells. Just like a meal contains different types of food like rice, lentils, and fish, our blood also contains different types of cells. All these types of blood cells are produced through the process of
hematopoiesis . Let's see what they are.
Red blood cells (Erythrocytes)
These are the most abundant type of cells in our blood. Did you know that the main function of red blood cells is
to carry oxygen that enters the lungs when we breathe to all the other organs and tissues throughout the body. These cells work like an oxygen tank. Also, these red blood cells help to bring the unwanted carbon dioxide that is produced in our body back to the lungs and get it out when we exhale. The process of producing red blood cells is called
erythropoiesis .
White blood cells (Leukocytes)
White blood cells are like the security guards in our bodies. Like an army that protects a country, these cells
protect us from diseases by fighting germs, such as bacteria and viruses, that enter our bodies. Not only that, these white blood cells also help destroy abnormal cells that grow inside our bodies, such as cancer cells. The process by which white blood cells are produced is called
Leukopoiesis. There is not just one type of white blood cell, but several main types: Among these, neutrophils, basophils, and eosinophils have very similar functions, so they are collectively called granulocytes . Platelets (or Thrombocytes)
Platelets are like little doctors in our bodies. When you have a small wound and start to bleed, these platelets help to stop the bleeding. These are sticky, small cell fragments. They gather at the site of the wound, form a clot, and seal the wound. It's like putting on a plaster. This is why blood doesn't leak out of our bodies unnecessarily. The process of producing platelets is called thrombopoiesis . A very important question! This amazing process called hematopoiesis mainly occurs in a spongy part inside our bones. We call this bone marrow. Have you seen the red part inside the bone when you eat chicken? That's what this bone marrow is like. The formation of blood in this way inside the bone marrow is called medullary hematopoiesis . The blood cells that are formed in this way then travel throughout our body through our blood vessels. However, sometimes, especially in certain disease conditions, blood can be produced in other parts of our body in addition to the bone marrow, for example, in organs like the liver and spleen . The formation of blood outside the bone marrow in this way is called extramedullary hematopoiesis . There are slight changes in the place where this blood is formed, both before and after we are born. Before birth
This blood begins to form while we are still in our mother's womb, that is, as an embryo.- First, during the first 3 weeks of pregnancy, a type of red blood cell begins to form in a structure around the embryo called the yolk sac . These are slightly less developed than the red blood cells we produce as adults.
- Then, around 2-3 months into pregnancy, red blood cells and platelets begin to form in the liver and spleen. White blood cells are formed in the liver, spleen, and thymus gland.
- By the fifth month of pregnancy, most of the blood production occurs in the bone marrow. However, some types of white blood cells are also produced in the thymus gland, spleen, and other lymph tissues.
After birth
After we are born, from infancy to adulthood, most of our blood production occurs in the bone marrow. However, a special type of white blood cell called lymphocytes also develops in our thymus gland. However, in some disease states, for example, if the bone marrow is unable to make blood cells properly, our body tries to make blood again in the places where blood was made before birth, such as the liver, spleen, or lymph nodes. This is like a strategy used in an emergency. How does the process of hematopoiesis occur?
This is a very complex, yet very orderly process. Just think of how many different types of blood cells can be formed from a single stem cell! All of these blood cell types have a common, starting cell. We call this a hematopoietic stem cell (HSC) . This is like a "master cell." This HSC cell first develops into a precursor cell or "blast" cell . This precursor cell is a cell that is on its way to becoming a specific blood cell, but is not yet fully developed. This precursor cell then undergoes several more cell divisions and changes before it becomes a fully developed, functional blood cell. There are three main parts of hematopoiesis, based on how the three types of blood cells we discussed earlier are formed:- Erythropoiesis: Production of red blood cells.
- Leukopoiesis: Production of white blood cells.
- Thrombopoiesis: Production of platelets.
With all these changes, that original stem cell (HSC) becomes more and more specialized. That is, it loses the characteristics of a stem cell and gains the characteristics of a red blood cell, white blood cell, or platelet. Red blood cells are made in our bone marrow. The primary blood cell (HSC) first becomes a precursor cell called an erythroblast . This erythroblast then becomes an immature red blood cell called a reticulocyte . Finally, this reticulocyte becomes a fully developed, functional red blood cell.Not all white blood cells are created the same way. The granulocytes we discussed earlier - that is, basophils, eosinophils, and neutrophils - are created in a slightly different way than the monocytes and lymphocytes. How granulocytes are formed
All three types of granulocytes are produced in the bone marrow. When a primary blood cell (HSC) goes on to make them, it develops along a pathway called the myeloid cell line . The word "myeloid" means "related to the bone marrow." So, these cells are named because they are produced in the bone marrow. To make a granulocyte, the HSC cell first becomes a precursor cell called a myeloblast . This myeloblast then becomes a myelocyte , which ultimately differentiates into a basophil, eosinophil, or neutrophil. How mononuclear cells are formed
Monocytes are produced in the bone marrow. Lymphocytes - that is, B-cells, T-cells and natural killer cells - are produced in the bone marrow and other lymphoid tissues, such as the thymus gland. For example, lymphocytes are formed in the bone marrow at a very young age, and then migrate to the thymus gland, where they mature into T-cells.- Monocytes develop through the myeloid cell line : Because they are also formed in the bone marrow, they first develop into a precursor cell called a monoblast , and only then do they become fully developed monocytes.
- Lymphocytes develop along the lymphoid cell line: because they are formed in lymphoid tissues, such as the bone marrow and thymus gland. Therefore, the HSC cells that become lymphocytes develop into precursor cells called lymphoblasts . These are the ones that eventually differentiate into T-cells, B-cells, or natural killer cells.
Platelet production also occurs in the bone marrow. Here, a primary blood cell (HSC) first develops into a precursor cell called a megakaryoblast . This megakaryoblast then develops into a large cell called a megakaryocyte . Finally, platelets are formed when parts of this megakaryocyte break down. Isn't it amazing? How long does this process of hematopoiesis take?
In fact, the rate at which blood cells are produced depends on your body's needs. For example, if you get sick, your body increases its production of white blood cells to fight germs. Normally, the process of hematopoiesis occurs continuously, because blood cells also have a certain lifespan. When one blood cell dies, a healthy body makes a new one to replace it. The average lifespan of blood cells is as follows:- Red blood cells: Live about 120 days.
- White blood cells: Live from a few hours to a few days.
- Platelets: Live between 5 and 9 days.
So, our body is constantly getting rid of these old cells and continuing to make new ones.
What if there is a problem with the hematopoiesis process?
Our bodies are very good at controlling the production of these blood cells, meaning we have exactly the right amount of blood cells. However, some medical conditions can disrupt this process of hematopoiesis. This can result in either too few blood cells being produced or too many. If the number of blood cells changes abnormally in this way, various symptoms and medical conditions can occur.- Problems with red blood cells:
- If your red blood cell count decreases, it's called anemia . You may feel tired and weak because your body's tissues don't get enough oxygen.
- An increase in the number of red blood cells is called erythrocytosis . In mild cases, this can cause some uncomfortable symptoms. However, in severe cases, the increase in red blood cells can cause the blood to thicken, increasing the risk of heart attack or stroke.
- Problems related to white blood cells:
- If your white blood cell count decreases, it is called leukopenia . This increases your risk of developing infections.
- An increase in the number of white blood cells is called leukocytosis . This is usually a sign of an infection. However, sometimes a very high white blood cell count can be a sign of a blood disease or cancer.
- Platelet-related problems:
- A low platelet count is called thrombocytopenia . This condition can cause you to bleed more easily and bruise more easily.
- If the platelet count increases, it is called thrombocytosis . This increases the risk of developing serious blood clots.
What are the conditions that interfere with the process of hematopoiesis?
There are a number of factors that can interfere with the process of hematopoiesis. Some of these can have mild effects, while others can be severe. For example, as we age, fat can build up in our bone marrow, which reduces the ability to make blood. Blood-related diseases and blood cancers , such as leukemia, lymphoma, and myeloma, can also interfere with the production of blood cells. These diseases cause an overproduction of abnormal, diseased blood cells. Another thing is that some medications can interfere with the process of hematopoiesis, causing a decrease in the number of blood cells. For example, chemotherapy, which is used to destroy cancer cells, can cause a decrease in the number of white blood cells. This is called neutropenia . So, some medications can also cause a decrease in blood cells as a side effect. The most important thing we want to take home from this story (Take-Home Message)
Okay, so now you understand that this hematopoiesis, the process of blood formation that we talked about today, is something that happens constantly, something that is essential for our healthy existence and survival. This steady blood supply is very important for supplying oxygen to our body's tissues and protecting us from disease. Remember, this process mostly happens inside our bone marrow. Many things that affect our health can also affect this blood-making ability.
Therefore, maintaining our overall health by eating a balanced diet, exercising, and following medical advice will help to keep this amazing process of hematopoiesis running smoothly. If you have any further questions about this, never be afraid to talk to a doctor.
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