M2 Notes
MODULE TWO
M2L1
Slide 1
The process that generates all of our blood cells is called hematopoesis. This multistep process takes place mostly in the bone marrow. Hematopoiesis actually starts in embryonic development at a different site called the yolk sac, but at this early stage, only a few types of cells are generated. The process moves to other places, such as the fetal liver, but at birth, most hematopoiesis occurs in the bone marrow.
At any given time, there is a hierarchy of cells in the bone marrow, each stage or level characterized by the potential to differentiate or to expand in large numbers by cell division. The proliferation potential decreases as the cell proceeds from a more primitive or undifferentiated state to a more differentiated state.
Slide 2
For such a complex process, it is amazing that the number of blood cells for each type remains the same under steady-state conditions. Feedback mechanisms are in place to ensure that just the right number of cells for each type is generated to meet the individual’s needs for oxygen delivery, immune defense, and maintenance of vascular integrity.
Under certain conditions, as in hemorrhage or infection, just the right type of blood cell is expanded to compensate for the loss or to meet the demands of the individual. Red blood cell proliferation and differentiation increase with acute blood loss. White blood cells increase in number during acute infection. In the absence of serious pathology, the blood system returns to its basal state once the needs of the individual are met.
Blood system homeostasis is ensured by an adequate supply of bone marrow stem cells, which remain small in number, but are able to meet the demands through the process of self-renewal. Part of the stem cell progeny commits to a specific lineage of blood cells, after which they expand and differentiate on a particular pathway. When cells emerge from the bone marrow and go into circulation and in tissues to carry out
M2L1
Slide 1
The process that generates all of our blood cells is called hematopoesis. This multistep process takes place mostly in the bone marrow. Hematopoiesis actually starts in embryonic development at a different site called the yolk sac, but at this early stage, only a few types of cells are generated. The process moves to other places, such as the fetal liver, but at birth, most hematopoiesis occurs in the bone marrow.
At any given time, there is a hierarchy of cells in the bone marrow, each stage or level characterized by the potential to differentiate or to expand in large numbers by cell division. The proliferation potential decreases as the cell proceeds from a more primitive or undifferentiated state to a more differentiated state.
Slide 2
For such a complex process, it is amazing that the number of blood cells for each type remains the same under steady-state conditions. Feedback mechanisms are in place to ensure that just the right number of cells for each type is generated to meet the individual’s needs for oxygen delivery, immune defense, and maintenance of vascular integrity.
Under certain conditions, as in hemorrhage or infection, just the right type of blood cell is expanded to compensate for the loss or to meet the demands of the individual. Red blood cell proliferation and differentiation increase with acute blood loss. White blood cells increase in number during acute infection. In the absence of serious pathology, the blood system returns to its basal state once the needs of the individual are met.
Blood system homeostasis is ensured by an adequate supply of bone marrow stem cells, which remain small in number, but are able to meet the demands through the process of self-renewal. Part of the stem cell progeny commits to a specific lineage of blood cells, after which they expand and differentiate on a particular pathway. When cells emerge from the bone marrow and go into circulation and in tissues to carry out