[Biology Class Notes] on Erythropoiesis Pdf

Every organ in our bodies is designed to function like a finely tuned machinery where everything has to work in sync to stay healthy and survive. However, there are often cases when something goes wrong, and we end up getting diseases or other critical medical conditions.

Similarly, there can be cases when our body is unable to produce the required amount of red blood cells leading to different conditions. This is when doctors take help from the natural mechanism process called erythropoiesis that helps produce more red blood cells to treat different conditions such as anemia, sickle cell disease, and more.

What is Erythropoiesis?

Erythropoiesis is one of our bodies’ most complex natural procedures to produce mature red blood cells from hematopoietic cells. These newly produced mature red blood cells are then used to replace the old red blood cells. One needs different growth factors paired with element iron, used by the erythroid precursor cells to ensure normal erythropoiesis with effective erythroid differentiation.

Further, it is important to note that our body requires a key hormone called erythropoietin or EPO for proper erythropoiesis. Our body also requires essential minerals such as iron because it is the key ingredient needed to produce hemoglobin. Any erythropoiesis without erythropoietin and iron will always be classified as ineffective erythropoiesis or iron-deficient erythropoiesis.

Erythropoietin helps the erythroid precursor cells survive and reproduce by generating different intracellular signals that help prevent apoptosis. During normal erythropoiesis, it is imperative to monitor and even regulate iron availability to maintain the ideal amount of iron for producing the right amount of haemoglobin. Iron as a mineral is competent enough to regulate globin synthesis at both translational and transcriptional levels. Many more studies are being conducted on erythropoiesis to better understand different sites of erythropoiesis, reasons leading to ineffective erythropoiesis, or iron-deficient erythropoiesis.  

Different Sites of Erythropoiesis

The site of erythropoiesis does not remain constant, and as we grow, the site of erythropoiesis also keeps on changing. Therefore, let us dive deeper and get an enhanced understanding of the ever-changing site of erythropoiesis.

 

The Fetal Life 

The very first stage of erythropoiesis takes place when the baby is still a fetus. Erythropoiesis in this primitive stage can further be divided into three different stages that include:  

• Mesoblastic Stage: The initial two months when the unborn child is alive inside the uterus, the red blood cells required are produced from the mesenchyme of the yolk sac through megaloblastic erythropoiesis.

• Hepatic Stage: This stage begins when the fetus enters the third month of being alive inside a uterus. From this stage, the liver takes over the job of producing red blood cells along with other organs such as the lymphoid and spleen. 

• Myeloid Stage: This is the last stage that constitutes the last three months of intrauterine life, and at this stage, the red blood cells are produced by the liver and red bone marrow.

New Born, Children and Adults   

Now that a human is born and this changes the site of erythropoiesis, and even this stage of life is further divided into two different stages that include:

• The First Twenty Years: In the first twenty years of our lives, the red blood cells within the body are produced from the red bone marrow of all the bones in our body. This includes both flat and long bones, so many even call this bone marrow erythropoiesis process.  

• After the Initial Twenty Years: After we have passed the age of twenty, all our red blood cells are produced by different membranous bones that include the ribs, vertebrae, scapula, sternum, skull bones, and iliac bones. Additionally, in normal erythropoiesis, red blood cells are also produced from the end of long bones in this stage.   

Nonetheless, it is worth noting that even though bone marrow is the primary site for producing all blood cells, both red and white, only one-third of bone marrow is used to produce erythrocytes, while the remaining two-thirds is used to produce leukocytes. 

Different Stages of Erythropoiesis

As mentioned earlier, erythropoiesis is a complex process, and the entire process can be divided into many different stages. These stages include: 

• Pre-erythroblast: The stage is also called megaloblast erythropoiesis, where the production or synthesis begins, and the very first cells are derived from CFU-E.

• Early Normoblast: Unlike megaloblast erythropoiesis, in this stage, the nucleoli inside the nucleus disappear, and the condensation of the chromatin network begins.  

• Intermediate Normoblast: Here, the chromatin network condenses further, and the haemoglobin begins to appear.

  

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Did You Know?

• Our body produces about 2.5 billion red blood cells every day by leveraging hematopoiesis and erythropoiesis.

• Chronic kidney diseases can result in severe anemia, further making erythroid differentiation more challenging.

• Our body requires seven days for developing and maturing red blood cells, where five days are needed in the reticulocyte stage and two more days for the RBC to mature in the last stage.