Quick notes on Hematopoiesis and brief into about the types of cells are forming during the process. For UG and PG students. Different colors, themes and video is used to make it more interesting and easy to go through the contents.

1. PRANJAL SHARMA
20-PZO-016
HEMATOPOIESIS

2. Hematopoiesis Definition
Hematopoiesis is the production of all of the cellular components
of blood and blood plasma. It occurs within the hematopoietic
system, which includes organs and tissues such as the bone
marrow, liver, and spleen.
Simply, hematopoiesis is the process through which the body
manufactures blood cells.

4. There are three distinct lineages of blood cells:
1. Erythroid Lineage, which consists of reticulocytes and
erythrocytes (red blood cells).
2. Lymphoid Lineage, which consists of lymphocytes (B and T
cells) as well as natural killer cells.
3. Myeloid Lineage, which consists of macrophages, dendritic cells,
granulocytes, and megakaryocytes, among others.

5. The Process of Hematopoiesis
● The rate of hematopoiesis depends on the body’s needs. The body continually manufactures new
blood cells to replace old ones. About 1 percent of the body’s blood cells must be replaced every
day.
● White blood cells have the shortest life span, sometimes surviving just a few hours to a few days,
while red blood cells can last up to 120 days or so.
● The process of hematopoiesis begins with an unspecialized stem cell. This stem cell multiplies, and
some of these new cells transform into precursor cells. These are cells that are destined to become a
particular type of blood cell but are not yet fully developed. However, these immature cells soon
divide and mature into blood components, such as red and white blood cells, or platelets.
● Although researchers understand the basics of hematopoiesis, there is an-ongoing scientific debate
about how the stem cells that play a role in hematopoiesis are formed.

7. Stages of Hematopoiesis
Mesoblastic stage-first month of embryonic life where cells are
formed outside the embryo in the mesenchyme of the yolk sac.
Hepatic stage-by the 6th week
Medullary stage- by the 5th month blood cell formation occurs in
the bone marrow.
MarrOW primitive stem cells & Committed progenitor cells are
confined
-Spleen & lymph nodes secondary lymphoid tissue for
lymphocyte development and differentiation.

8. Stages of Hematopoiesis
Mesoblastic stage-first month of embryonic life where cells are
formed outside the embryo in the mesenchyme of the yolk sac.
Hepatic stage-by the 6th week
Medullary stage- by the 5th month blood cell formation Occurs in
the bone marrow.
MarrOW primitive stem cells & Committed progenitor cells are
confined
-Spleen & lymph nodes 2ndary lymphoid tissue for lymphocyte
development and differentiationn.

11. Types of cells involved in the process
Each type of blood cell follows a slightly different path of hematopoiesis. All begin as
stem cells called multipotent hematopoietic stem cells (HSC). From there,
hematopoiesis follows two distinct pathways.
Trilineage hematopoiesis refers to the production of three types of blood cells: platelets,
red blood cells, and white blood cells. Each of these cells begins with the
transformation of HSC into cells called common myeloid progenitors (CMP).
After that, the process varies slightly. At each stage of the process, the precursor cells
become more organized:

12. Red blood cells and platelets
● Red blood cells: CMP cells change five times before
finally becoming red blood cells, also known as
erythrocytes.
● Platelets: CMP cells transform into three different cell
types before becoming platelets.

13. White blood cells
There are several types of white blood cells, each following an individual
path during hematopoiesis. All white blood cells initially transform from
CMP cells into to myeoblasts. After that, the process is as follows:
● Before becoming a neutrophil, eosinophil, or basophil, a myeoblast
goes through four further stages of development.
● To become a macrophage, a myeoblast has to transform
three more times.

14. T cells and B cells
To produce lymphocytes, MHCs transform into cells called common
lymphoid progenitors, which then become lymphoblasts. Lymphoblasts
differentiate into infection-fighting T cells and B cells. Some B cells
differentiate into plasma cells after exposure to infection.

16. Factors Regulating Erythropoiesis.
● The major growth factors regulating in vivo erythropoiesis are
granulocyte colony-stimulating factor (G-CSF), granulocyte
macrophage colony-stimulating factor (GM-CSF),
interleukin- (IL-) 3, stem cell factor (SCF), IL-1, IL-6, IL-4,
IL-9, IL-11, insulin growth factor-1 (IGF-1), and
erythropoietin (EPO).
● Also, Vitamin B12 ,Folic Acid, Vitamin C, Iron ,Copper
,Calcium, Bile salt ,Cobalt and Nickel.

17. T cells and B cells
To produce lymphocytes, MHCs transform into cells called common lymphoid
progenitors, which then become lymphoblasts. Lymphoblasts differentiate into
infection-fighting T cells and B cells. Some B cells differentiate into plasma cells
after exposure to infection.

18. Facts of Hematopoiesis
● In a healthy adult person, about 1011–1012 new blood cells are
produced daily to keep steady state levels in the blood circulation.
● There are 150 Billion red blood cells in one ounce of blood.
● There are 2.4 Trillion red blood cells in one pint of blood.
● The human body manufactures 17 million red blood cells per
second. ...
● A red blood cell is around 7 microns in size.
● We can store blood for 42 days if we do not freeze it. Frozen
blood can be stored ten years, but freezing blood is a poor way of
storing it. Generally speaking, we store blood in the refrigerator,
where we can store it for up to 42 days.

19. Significance of Erythropoiesis
Erythropoiesis, the development of red blood cells, is a tightly
regulated process for maintaining sufficient oxygen delivery to
tissue. Oxygen delivery is proportional to the concentration of
oxyhemoglobin (the hemoglobin level x oxygen saturation) and
cardiac output.

21. Conclusion

22. Possible Question from the Chapter
● Explain the process of Hematopoisis.
● What are the different types of blood cell?
● What is the major site of blood production in adults?
● Factors responsible for hemopoisis.
● How many types of blood formation lineages are their?
● Write the Life span of RBC ,WBC and Platelets
Respectively.

23. References
● https://www.medicalnewstoday.com/articles/319544#hematopoiesis-
and-health
● https://en.wikipedia.org/wiki/Haematopoiesis
● https://biologydictionary.net/hematopoiesis/
● https://www.news-medical.net/life-sciences/Hematopoiesis-
Process.aspx
● Principles of Anatomy and Physiology,Book by Bryan H. Derrickson
and Gerard J. Tortora
● Immunology,Textbook by Barbara Anne Osborne and Janis Kuby