Lecture 16 - Haemopoiesis Flashcards
What is haemopoiesis?
What kind of cells are blood cells derived from?
- The production of blood cells and platelets that occurs in bone marrow
- From haemopoietic stem cells which become common myeloid & lymphoid progenitor cells - these progenitor cells must differentiate into their lineage bound cells driven by multiple hormone and chemical messengers.
What is meant by the term “selection” in terms of haemopoiesis?
Selection means that not all blood cells produced make it out of the bone marrow. 250 mil erythrocytes produced per day - only 40% of progenitor cells survive. Many are killed via apoptosis (particularly if they are not adequately synthesised, as a way of quality control).
What is the process by which erythrocytes are formed from common myeloid progenitors? What growth factor is required?
What features do RBC’s have?
- Erythropoiesis
- Erythropoietin
- Last 120 days, degraded by liver/spleen - take 20 seconds to circulate entire body, 7um in diameter.
How does the structure/contents of erythrocytes relate to its function?
1) Biconcave to increase SA for diffusion of gases
2) No nucleus to maximise oxygen holding capabilities
3) No mitochondria to ensure no oxygen is used up
4) Contain Hb to increase affinity of oxygen binding
Describe what happens from a proerythroblast to the RBC stage during erythropoiesis.
What is the cell in the final step before a mature erythrocyte is formed? How much RNA remains?
What does high amount of this cell in the blood tell us?
- Starting with a pro erythroblast, there is a large nucleus and lots of RNA. The cell nucleus gradually shrinks and RNA is moved along with it.
- Reticulocytes, retain tiny bit of RNA to make Hb, this is removed in 1-2 days
- High amounts in blood indicate significant blood loss (as more RBC’s are clearly being synthesised).
What is erythropoietin released in response to and from where?
How does erythropoietin increase RBC population?
Where is erythropoietin made and stored?
- Erythropoietin is a glycoprotein released from the kidney after it senses hypoxia (low O2 levels) - e.g.: via blood loss
- This stops apoptosis of erythrocyte progenitor cells
- It is made in the liver during fetal life and taken over by the kidney at birth.
What is granulopoiesis?
Why are granulocytes named granulocytes?
What do they do?
What are the 3 main types of granulocyte?
- Production of granulocytes within bone marrow
- Due to abundant presence of granules in their cytoplasm
- Mediate inflammatory reactions by releasing cytokines, IL’s & leukotrienes.
- Neutrophil, eosinophil & basophil
What are neutrophils?
What does their nucleus look like?
What are their functions?
- The most abundant WBC (60%) and the first line defence against bacteria (10-15um).
- Multilobuled nucleus with lots of granules in cytoplasm
- They kill bacteria via phagocytosis (granule contain lysozymes, metalloproteinases & gelatinises) , are involved in antigen presentation and produce neutrophil extracellular traps (NETS) as well as undergoing respiratory burst (producing free radicals to destroy bacterial DNA).
What growth factor stimulates granulocyte production? When is it released?
How does it do this?
- Granulocyte-colony stimulating factor (G-CSF)
- In response to inflammation
- by acting on bone marrow, increasing the number of circulating neutrophils or making them mature faster.
What are the role of basophils?
What does their nucleus look like?
What do their granules contain?
- Release histamine which causes vasodilation & mediates hypersensitivity reactions.
- Bilobed nucleus (2 lobes)
- Histamine & Heparin - histamine dilates blood vessels so there is increased blood flow triggering inflammation.
What do eosinophils do?
What does their nucleus look like?
What do their granules contain?
What do all 3 lineages of granulocytes go through the process of?
- Phagocytose pathogens and fight parasitic worms
- 2 nuclear lobes
- Anthelminthic proteins to fight parasitic worms and cell component destroying enzymes.
- Nuclear condensation + lobulation to produce increased numbers of granules.
What are monocytes called when they are in tissues?
What is the role of these cells?
What does their nucleus look like?
- Monocytes in blood, macrophages in tissues
- First line of defence, to phagocytose pathogens and present foreign antigens
- Unilobular horse shoe nucleus
What is thrombopoiesis?
What is the role of thrombocytes?
What are their main features?
- Formation of thrombocytes (platelets) in bone marrow
- Have special receptors in surface that cause aggregation of platelets
- No nucleus, biconvex shape, contain vast amounts of proteins and clotting factors & gpllb/gpllla surface receptors which mediate aggregation.
How does thrombopoiesis occur and what is it upregulated by?
- Breakdown of each megakaryocyte creates 2-3,000 platelets
- Upregulated by thrombopoietin in the liver
What is lymphopoiesis?
The production of lymphocytes (T, B & Natural Killer cells)
