Hematopoiesis Flashcards
Hematopoiesis
Continuous replacement of RBCs
Where is the prenatal site for Hematopoiesis?
Yolk sac, liver, spleen, lymph node, bone marrow
Where is the postnatal site for Hematopoiesis?
Bone marrow of all bones in young animals
Sternum, vertebrae, ribs, skull, pelvis and epiphyses of long bones in adult animals
Stem cells involved in hematopoiesis
Pluripotent
Multipotent (lymphoid and myeloid)
Unipotent
Where do all blood cells develop from?
A pluripotent stem cell in the bone marrow
What do pluripotent stem cells gives rise to?
Myeloid multi-potential stem cell and Lymphoid- multi potential stem cell
What do myeloid multi-potential stem cell give rise to?
All blood cells except lymphocytes
What do lymphoid multi-potential stem cells give rise to?
Lymphocytes
What do B lymphocytes do? (Lymphopoiesis)
Differentiate from precursor cells in the bone marrow
Acquire B cell-specific surface makers
(Humoral activity)
What do T cells do? (Lymphopoiesis)
Migrate into the thymus where they acquire T cell-specific surface makers
Cell mediated
Diapedesis
Leukocytes migrating from bone marrow into the sinusoid
Stages in development of RBC
1.Reticulum (CFU-E)
2. Rubriblasts
a. decrease cell size
b. Increase Hb synthesis
3. Prorubicyte
a. Loss of cytoplasmic granules
b. Increase in cytoplasmic eosinophilia
4. Rubicyte (normoblast)
a. Increase in condensation of chromatin nucleus (loss
of nucleus
5. Metarubricyte
—- no mitosis—–
6. Reticulocyte
7. Erythrocyte
What does CFU stand for?
Colony forming unit
Erythropoietin
Hormone secreted by the kidneys that increases RBC production rate, in response to oxygen levels falling in tissues.
Reticulocytes in ruminants
No reticulocytes in healthy animals
In anemic animals
Reticulocytes in dogs and cats
1-2% in blood of healthy animals
Increase in number in anemic animals
What is the increase of reticulocytes during anemia?
Polychromasia
Staining of reticulocytes
Slides with basic dyes because they contain polyribosomes (basophilic strands)
EX: Methylene blue
Stages in the development of granulocytes
Seen in goodnotes
Left shift
The body responding to an inflammatory stimulus
Bone marrow releasing more immature forms of neutrophils (band cells)
Regenerative left shift
Leukocyte count elevated with neutrophilia and high numbers of mature neutrophils than immature
Degenerative Left Shift
Demand for neutrophils increase, bone marrow stores depleted, marrow will release mainly immature neutrophils
What are the affects of degenerative left shift?
Leukocyte count will drop (leukopenia)
Mature neutropenia will develop
Number of immature neutrophils will be greater than the number of mature
Proliferation of hematopoietic stem cells and progenitor cells
Cannot occur spontaneously
Requires the presence of specific hematopoietic growth factors (HGFs, hematopoietic cytokines)
What does erythropoietin do?
Prolongs the survival of erythroid precursors
Shortens time between cell divisions
Increases number of cell produced from individual precursors
Stimulates Hb synthesis in dividing erythroid cells
What is the source of erythropoietin?
Peritubular interstitial cells located in the inner cortex and outer medulla of kidney (85-90%)
Specific hepatocytes and Ito cells in liver (10-15%)
Thrombopoietin
Regulates development of megakaryocytes from hematopoietic stem cells and level of platelets in the blood
Where is thrombopoietin produced?
Liver
Granulocyte Colony-Stimulating
Stimulates growth and differentiation of neutrophils
Produced by monocytes, macrophages, fibroblasts, stromal cells, endothelial cells
Development of monocytes
- CFU-G (granulocytes)
- Monoblast
- Promonocyte
- Monocyte (macrophage in the CT)
Development of Platelets
- CFU-MK
- megakaryocyte
- Platelets
