Haematopoiesis Flashcards
What is haematopoiesis?
Production of RBCs
Leucocytes and platelets produced in haemopoietic tissue
What happens to ageing or damaged blood cells?
Cell components recycled or removed by macrophage
Give an example of when there might be a haematopoiesis arrest. What is the first clinical sign of this?
Chemotherapy
Neutrophenia
What is the lifespan of an RBC?
1-5 months
Bird
What is the lifespan of platelets?
10 days
Put the blood cells in order of longest to shortest life span
Lymphocytes - weeks to years
RBCs - 1- 5 months
Platelets - 10 days
Monocytes - days, transform into macrophages in tissues
Neutrophils - live less than 10 hours in blood, 24-48 in tissues
Which WBC has the longest and shortest life span?
Longest - lymphocyte (weeks to years)
Monocytes live days, transform into macrophages in tissues
Shortest - neutrophils (<10 hrs in blood, <2 days in tissue)
Where is the major site of haematopoiesis?
Bone marrow
Primary in long and flat bones
First evident in yolk sac of embryo
Later in embryonic life occurs in liver and spleen
Birth = red bone marrow (long bone, vertebrae, pelvis, skull
What cells are found in bone marrow?
Endothelial cell Macrophage Stromal cell Developing granulocytes Megakaryocyte
What do stromal cells in bone marrow produce?
Haematopoietic regulatory molecules
What are the 2 cells that multipotent haematopoietic stem cells can form?
Common myeloid progenitor
Common lymphoid progenitors
What cells do common lymphoid progenitors form?
All lymphocytes:
Natural killer cell Small lymphocyte (which forms T and B lymphocytes)
What cells do common myeloid progenitors form? 4 cells - all begin with M except one
Give rise to all other blood cells (not lymphocytes as thats what lymphoid progenitors give rise to) RBC Mast cell Megakaryocyte Myeloblast
Which cells produce WBCs?
Myeloblast
Bone marrow is only part of lymphogenesis (production of lymphocytes). Where do they migrate to, mature and proliferate?
Lymphoid organs - lymph nodes, thymus, spleen
What feature makes T and B lymphocytes unique (after antigen encounter)?
Maintain memory of an antigen encounter
What are reactive lymphocytes?
Cytotoxic lymphocytes made due to antigen stimulation
What is myelopoieses? What main cell does this arise from?
Production of all blood cells
Common myeloid progenitor
Where does myelopoiesis take place?
Bone marrow
Proliferative pool, maturation pool and storage pool
What cells are mainly found in the storage pool of bone marrow?
Mature (segmented) neutrophils
What stimulates granulocytopoiesis and monocytopoiesis? When are these produced?
Granulocyte-macrophage colony stimulating factor (GM-CSF)
Macrophage colony stimulating factor (M-CSF)
Presence of infection or inflammation
Which cells are able to provide negative feedback to their own production?
Neutrophils
In homeostasis, what neutrophils are seen in circulation? When may other types of neutrophil be seen?
Segmented (mature neutrophils) Band cells (immature neutrophils) released with inflammation
How does number of neutrophils in circulation differ between moderate inflammation and very acute severe inflammation? Why?
Mild/moderate inflammation - neutrophiliia due to release from storage pool and increased myelopoiesis
Acute, severe inflammation - neutropenia, due to consumption of neutrophils
What do eosinophils produce that allow them to be their own progenitor?
Interleukin 5 (IL-5) Cytokine for growth, differentiation and activation of eosinophils
Where are mast cells produce? Where do they mature?
Produced in bone marrow
Mature in tissue
Are mast cells common or rare in circulation? When may they be seen?
Rare
Seen in dog/horse trauma and inflammation
Seen in cat neoplasia
What are mast cells? Where are they found? What do they release?
Cells containing basophil granules
Found in connective tissue
Release histamine during inflammation
Why can’t RBCs undergo mitosis or repair when older/damaged?
No nucleus
No organelles
What % of RBCs are destroyed each day? Why doesn’t this cause anaemia?
1% destroyed
1% release of new RBCs
What do immature RBCs start as?
Blast cells - large, blue with nucleus
Describe what happens to blast cells as they mature
Divide and become smaller
Haemoglobin concentration increases (makes red)
Nucleus removed
Released into marrow sinus - lose organelles and DNA= mature
What cell is the last immature RBC with a nucleus?
Normoblast
What cell is an immature RBC without a nucleus?
Reticulocyte
What colour are normoblasts? Are they seen in circulation?
Blue - containing proteins and nucleus
No - unless accelerated haematopoiesis or bone marrow damage
How long does it take for RBCs to mature in the blood? Which species takes slightly longer and why?
24 hrs
Cat - spleen less efficient, may have organelles for longer
What process produces megakaryocytes?
Endomitosis - nuclear division but no cellular division
Produces megakaryoblasts
How are platelets formed?
Endomitosis produces megakaryoblasts
Megakaryoblasts
What hormone mediates thrombopoiesis? Where is this produced?
Thrombopoietin
Mainly be liver
How does thrombopoietin differ from erythropoietin?
Thrombopoietin produced constantly
Self regulating - thrombopoietin destroyed by platelets/megakaryocytes
What hormone controls erythropoiesis? Where is this produced?
Erythropoietin
Kidneys
What minerals/vitamins are required for erythropoiesis?
Iron
Copper
B2, B6, B12
What could cause thrombocytosis?
Inflammation
Iron deficiency
