Haematopoiesis Flashcards
What is produced in haemopoietic tissue?
Leucocytes, erythrocytes and platelets
What are the lifespans of the following:
- RBC
- PLT
- WBC
- 1 - > 5months depending on species
- 10 days
- Hours to years depending on cell type
What is the lifespan of RBCs in a. dogs and b.cats
110 days
70 days
What is the lifespan of neutrophils?
<10 hours in blood and 24-48 once in tissues
Which WBC is long lived compared to the others?
Lymphocytes
Why is the lifespan of cells important in haematpoiesis?
If there is a sudden arrest of this process a reduction in neutrophils is the first thing we would notice - these play a vital role in innate immunity
What is the major site of haematopoiesis from birth?
Bone marrow
Name the stem cell category found in early embryos
Totipotent stem cells
Describe pluripotent stem cells
Found in the inner cell mass of the blastocyst
They are able to differentiate into almost all cells of the 3 germ layers, but not into an embryo
Describe multipotent stem cells
Found in most tissues
Can differentiate into a limited number of cell lineages
Limited in what the cells can become
Which stem cells give rise to all mature blood cell types?
Haematopoietic stem cells
What are the 2 sub-divisions of haematopoietic stem cells?
Common myeloid progenitor
Common lymphoid progenitor
Where do most stages of working lymphocytes form?
Thymus
What acts as a stimulant for lymphocyte division?
Contact with foreign material or antigen
Granulopoiesis and monocytopoiesis lead to the formation of?
Neutrophils, eosinophils, basophils and monocytes
Differentiation of neutrophils, eosinophils, basophils and monocytes is stimulated/controlled by what?
Cytokines (IL-3)
Colony stimulating factors
What is the role of inflammatory mediators (ILs and TNF) on granulopoiesis and monocytopoiesis?
They stimulate macrophages, fibroblasts and endothelial cell to produce cytokines such as G-CSF and GM-CSF which increase granulopoiesis and monocytopoiesis
Which cells make up the storage pool in granulocytopoiesis?
Segmented neutrophils
How can inflammation affect neutrophil numbers?
- Inflammation may cause increased neutrophils in blood (neutrophilia) due to release from the storage pool
But if inflammation is very acute and severe inflammation can also cause neutropenia due to consumption of circulating and stored neutrophils
Which cytokine is responsible for the growth and differentiation of eosinophils and the activation of mature eosinophils to kill helminth parasites?
IL-5
Why are erythrocytes unable to undergo mitosis?
No nucleus
Erythropoiesis is mainly controlled by … ?
Erythropoietin
What acts as a stimulus for erythropoiesis?
Hypoxia due to decreased RBC count
Decreased availability of oxygen to blood or increased tissue demands for oxygen
Causes the kidney to release erythropoietin
What are the 3 outcomes of iron ions broken down and left in blood?
- Used for the production of erythrocytes
- Stored as ferratin
- Excreted in bile (bilirubin)
What are the different cell stages in the production of an erythrocyte?
- Hemocytoblast (stem cell)
- Early and late stage erythroblasts
- Normoblast
- Reticulocyte
- Erythrocyte
When does cell division of the large RBC blast stem cell stop?
When optimal intracellular Hb concentration is reached
What colour do juvenile RBCs stain?
Blueish
What characteristic morphological changes take place during maturation from the rubriblast to the mature erythrocyte?
- cells become smaller
- nuclei become smaller and chromatin is more aggregated
- Nucleus is extruded
- cytoplasmic colour changes from blue to orange as haemoglobin is formed and RNA is lost
Describe endomitosis
Nuclear division but no cellular division which produces a megakaryoblast and then a megakaryocyte
How are platelets formed from a megakaryocyte?
Fragmentation of the megakaryocyte cytoplasm and shedding into blood produces platelets
What is the mediator of thrombopoiesis?
Thrombopoietin - produced by the liver
How does IL-6 affect thrombopoiesis?
It can increased thrombopoietin synthesis independently of PLT numbers
- able to increase PLT numbers even when they are lost/being destroyed
