Hematopoiesis Flashcards
Where does blood cell development occur in an embryo?
In the yolk sac
Where does blood cell development occur in a fetus?
From 6 weeks to 7 months it is predominantly in the liver and spleen; from 7 to 9 months, it is predominantly in the bone marrow.
In which bones is marrow most active in hematopoiesis in an adult?
The ribs, vertebrae, and sternum; the tibia and femur lose marrow by the mid 30s
How can the normal expected cellular content of the bone marrow be calculated?
100-age of patient is a decent indicator for how much of a patient’s bone marrow should be cellular versus fat
What are the main types of arterial supply to bone marrow?
Nutrient arteries and the periosteal capillary beds provide oxygen and nutrients to the marrow
How do blood cells enter circulation and how are premature cells blocked?
Mature blood cells enter the blood via endothelium lined sinusoids; adventitial reticular cells assure that cells leaving the sinusoids are mature. Cells enter the central vein (or sinus) thereafter
What types of cells exist outside the vascular network of the marrow?
1) Actively replicating hematopoietic cells–generate new cells
2) stroma (fat, macrophages, reticular cells, and fibroblasts)–supports structure
3) lymphoid tissue
4) nerves
5) trabecular bone
What are the roles of T-cells and macrophages in the bone marrow?
They produce growth factors that promote division and differentiation.
What is the first cell type in the morphogenic tree of hematopoietic cells?
The hematopoietic stem cells
How can hematopoietic stem cells be distinguished from other local cells?
They are CD34+ and lack lineage markers that would identify them as differentiated. They also are unlikely to be noticed dividing
What is the first branch of committed differentiation?
Myeloid cells (granulocytes, erythrocytes) and lymphoid cells
What are some properties of hematopoietic growth factors?
- Most are cytokines
- multiple factors can work on multiple cell lines
- produced by extravascular cells
- can act synergistically with other growth factors
What is the main growth factor involved in early differentiation?
c-kit ligand promotes early differentiation
What are two growth factors that promote myeloid development?
- IL-3
- granulocyte/macrophage colony stimulating factor
Which types of receptors are the primary targets of most growth factors?
JAK/STAT tyrosine kinases
What are the first two stages of erythroid development?
BFU-e (burst forming unit-erythroid) and CFU-e (colony forming unit-erythroid)
What hormone is the main trigger to promote differentiation from a BFU to a CFU, where is it produced, and under what conditions?
- Erythropoietin
- the kidney
- hypoxia
What are the six main stages of erythrocyte development?
1) Pronormoblast
2) Basophilic normoblast
3) Polychromatophilic normoblast
4) Orthochromatophilic normoblast
5) Reticulocyte
6) Erythrocyte
What do the stages of erythrocyte development show?
- -the extent to which hemoglobin has been produced
- -the extent to which the nuclear material has been eliminated
What is the different in content between a reticulocyte and an erythrocyte?
Reticulocytes still have some RNA in them that allows them to be stained a bluer color
About how long to red blood cells live?
120 days
What growth factors promote differentiation within the granulocyte tree?
G-CSF (neutrophils, basophils, eosinophils) and M-CSF (monocytes)
What are the stages of differentiation for most myeloid cells?
- Myeloblast
- Promyelocyte
- Myelocyte
- Metamyelocyte
- Band
What are the stages of differentiation for a monocyte?
- Monoblast
- Promonocyte
- Monocyte
