EXAM #1: HEMATOPOESIS Flashcards
What is the definition of hematopoiesis?
Formation of blood cells
Note that hematopoiesis provides the cellular elements of the peripheral blood i.e. leukocytes and RBCs.
Where does hematopoiesis occur?
Bone marrow
What is the lifespan of a lymphocyte?
Years
What is the lifespan of a RBC?
120 days
What is the lifespan of a platelet?
7-10 days
What is the lifespan of a granulocyte?
6-8 hours
Given the lifespan of granulocytes vs. RBCs; there are MORE granulocyte precursors in the bone marrow*
What cells are collectively called “granulocytes?”
- Eosinophils
- Mature segmented neurtorpils
- Basophils
What are hematopoietic stem cells?
Cells that give rise to progenitor cells of ALL lineages
List the characteristics of hematopoietic stem cells.
1) High proliferative potential
2) Capable of self-renewal and differentiation
3) Multipotential
Note that these cells CANNOT be identified morphologically.
What are bone marrow stromal cells?
Cells in the bone marrow that allow hematopoietic stem cells to develop
Describe the interactions between bone marrow stromal cells and hematopoietic stem cells.
These cell types bind together
- Tight binding the more immature the stem cell
- Looser binding the more differentiated
What is the role of cytokines in the bone marrow/ hematopoiesis?
Cytokines drive specific cell differentiation pathways
What is the difference between a progenitor cell cytokine and an end-stage cytokine?
Progenitor= act on immature cells
End-stage= act on more differentiated cell types
What is the role of G-CSF in hematopoiesis?
“Granulocyte Colony Simulating Factor”
- Released by macrophages at inflammatory sites
- Circulates to bone marrow
- Causes the production and release of NEUTROPHILS, basophils, and eosinophils
What is the role of EPO in hematopoiesis? What organ produces EPO? Why?
ERYTHROPOIETIN
- Production and release of RBCs in response to HYPOXIA
- Released by peritubular interstitial cells in the kidneys
What is the role of TGF-B in hematopoiesis?
Transforming Growth Factor- Beta
- DOWNREGULATION of cells in the bone marrow
What is the clinical utility of G-CSF?
1) Given to donors to release bone marrow stem cells into the peripheral blood
2) Stimulation of granulopoiesis following chemotherapy-induced marrow suppression.
Note that flow cytometry can be used to isolate bone marrow stem cells, to isolate them and give them to patients. Second, chemotherapy will commonly have a negative impact of granulocytes in the bone marrow. G-CSF will stimulate the production of these granulocytes to allow for more frequent chemotherapy, and decreased infection in the chemotherapy induced immunosuppressed state.
What is GM-CSF? What is the clinical utility of GM-CSF?
Granulocyte-Macrophage Colony Stimulating Factor
This is given to increase myeloid cell recovery in bone marrow transplant patients
What are the two different forms of bone marrow? Generally, what is the difference between the two?
Yellow= inactive Red= active
What type of marrow is present in the first few years of life?
Red
Where is red marrow located after age 18?
1) Ribs
2) Sternum
3) Pelvis
What is extramedullary hematopoiesis? Where can this take place?
This is hematopoiesis that occurs OUTSIDE of the bone marrow. It takes place in the:
1) Spleen
2) Liver
Generally, what happens to RBCs during erythropoiesis?
As the cell matures:
1) Cell size decreases
2) N:C ratio decreases
3) Nucleoli decrease in # and disappear
4) Cytoplasmic staining goes from darker blue to lighter blue
What is the definition of erythropoiesis?
Formation or production of RBCs
Where does erythropoiesis initially occur?
Embryonic yolk sac
Where does erythropoiesis continue after birth?
Liver and spleen, and then eventually transitions to bone marrow
What is a reticulocyte?
Immature RBC that is one step removed from mature
What is the normal percentage of reticulocytes?
1%
What is an elevated reticulocyte count an indication of?
- Bone marrow stress
- Increased need for new RBCs
What is the definition of granulopoiesis?
Production of granulocytes:
- Neutrophils
- Eosinophils
- Basophils
What is a band? What is a normal band count?
1 Step removed from a mature neutrophil
3-5%
What is an elevated band count an indication of?
Infection: the body is “kicking out” bands that will mature on the way to the site of infection
Specifically, bands are associated with BACTERIAL infection
What is the clinical nomenclature for an increased band count?
“Left shift”
This just refers to a shift the the left in the cell lineage.
What are the two pools of neutrophils?
Marginating= loosely attached
Circulating= circulating in the blood
Note that there is roughly a 50/50 ratio of these.
What organ/ cell is responsible for the removal of dead granulocytes?
Splenic phagocytes
What cell do macrophages develop from?
Monocytes
When does a monocyte become a macrophage?
Once it has migrated from the blood into the tissue
What is lymphopoiesis?
Production of lymphocytes:
- T-cells
- B-cells
- NK-cells
Where do B-cells mature?
Bone marrow
When do you get rid of self-reactive B-cells? What immunoglobulin/s is/are expressed at this time?
- Immature B-cell stage
- IgM
What is a mature B-cell?
B-cell expression IgM and IgD
Where do T-cells mature?
Thymus
Note that nearly 95% or prothymocytes that have come from the bone marrow to to the thymus, die in the thymus.
What is thrombopoiesis?
Production of platelets i.e. “thrombocytes”
What are the functions of platelets?
- Limit bleeding
- Repair endothelium
What are platelets i.e. what cell are platelets derived from?
- Anuclear cytoplasmic remnants of megakaryocytes
- Specifically, platelets come from long cytoplasmic extensions of megakaryocytes
What is the process that megakaryocytes undergo to produce platelets?
Endomitosis
What stimulates thrombopoiesis?
Thrombopoietin
What is the difference between an “absolute cell count” and a “differential count”
Absolute= quantity of each cell type
Differential= % of each cell type i.e. a relative count
Note that you must look at BOTH of these to determine NORMAL count.*
