Lecture 1 Hematopoiesis
2. Ontogeny of hematopoiesis
3. Description of the Hematopoietic Stem Cell (HSC)
4. The concept of the stem cell niche
5. Anatomical description of the stem cell niche
6. Functional description of the stem cell niche
7. Role of lineage-specific Growth Factors in hematopoiesis
8. The formation of mature blood elements: 1. Myelopoiesis
1. E rythrocytes
2. G ranulocytes
3. P latelets
9. The formation of mature blood elements: 2. Lymphopoiesis
1. T cells
2. B cells
3. N K cells
10. Bone Marrow Failure
1. I nherited disorders
2. A cquired disorders
The formed elements of the blood, such as red cells, white cells and platelets, play a vital role in the normal functioning of any human being. They are the end product of a highly specialized tissue calle d the bone marrow, which resides in the cavities of all bones of the body. The process through which formed elements of the blood are produced is called Hematopoiesis. Hematopoiesis can be envisioned as a hierarchical progression of multipotential hematopoietic stem cells that gradually lose one or more developmental options. They then become stem or progenitor cells committed to a single lineage.These single lineage progenitor cells then mature into the corresponding types of mature formed elements of the blood, also called peripheral-blood cells.
As we will see in the following chapters, the bone marrow can be divided into two major cellular compartments:
1. One composed with hematopoietic stem cells (HSCs) which have two major physiological properties: A.
Self renewal which is essential for the maintenance of life-long hematopoiesis, and: B Differentiation into committed progenitors. 2. The other composed of multipotent progenitor cells, which cannot renew, but rather divide and differentiate into all mature formed elements of the blood.
At first glance, the fact that the bone marrow tissue resides in the bone cavities of all bone does not imply that the bone itself has any role in the process of hematopoiesis. As a matter of fact, the mechanisms of bone and blood formation have traditionally been viewed as distinct unrelated processes. Compelling evidence now suggests that they are intertwined. It has been observed for a long time that HSCs are not randomly