Haemopoiesis Flashcards
What is haemopoiesis?
Formation of blood cells
What are the different mature blood cells?
Red cells Platelets Neutrophils Eosinophils Basophils Monocytes / macrophages Lymphocytes - B cells / T cells / NK cells
What cells are involved in modulating hypersensitivity reactions ?
Basophils
What cells are involved in destroying parasites and modulating hypersensitivity reactions?
Eosinophils
What cells are involved in phagocytosis and acute inflammation?
Neutrophils
What is the lifespan of red cells?
120 days
What is the life span of neutrophils?
7-8 hours
What is the lifespan of platelets?
7-10 days
Platelet precursor?
Megakaryocyte
Red cell precursor?
reticulocytes
Neutrophils and blast precursor?
Myelocytes
Where do precursor cells come from?
Haemopoietic progenitor cells
Where do progenitor and haemopoietic cells come from?
Haemopoietic stem cells
Where are haemopoietic stem cells derived from?
Mesoderm
Prenatally, when are circulating progenitors detectable from?
Week 5
Prenatal sites of haemopoiesis?
Yolk sack - stops by week 10
Liver - starts at week 6
Spleen - starts at week 12
Bone marrow - starts at week 16
Postnatally, where does haemopoiesis occur?
Bone marrow of :
- tibia ( stops about age 20)
- femur ( strops about age 25)
- vertebra
- sternum
- rib
What compartments make up the bone marrow??
Haemopoietic cells
Non haemopoietic cells
Connective tissue matrix
Vascular elements
What are the non haemopoietic cells in the bone marrow?
Adipocytes
Fibroblast
Osteoclasts
Osteoblasts
What about the sinus basement membrane ?
It is discontinuous
What is the process of mature cells being released from the bone marrow?
Blood cells pass through fenestrations in the endothelial cells and enter circulation
Release is associated with sinusoid all dilatation and increased blood flow
Neutrophils migrate towards sinusoid
Megakaryocytes extend proplatelets into sinusoid all blood vessels
What marrow is haemopoietically active?
Red marrow
What marrow is fatty and inactive?
Yellow marrow
What marrow increases with age?
Yellow marrow
An increase in yellow marrow has what result?
Reduction in marrow cellularity in older individuals
How do you assess haemopoiesis?
Blood count , Cell indices , Morphology ( blood film)
Bone marrow examination
Immunophenotyping
What factors regulate haemopoiesis?
Intrinsic factors of the cells Microenvironmental factors Erythroid maturation occurring with macrophages G-CSF - regulates neutrophil maturation Thrombopoietin regulating megakaryocytes
What are the micro environmental factors regulating haemopoiesis?
Haemopoietic stem cells occupy a niche
Niche is around vasculature which provides access to different signals
Niche can be altered in diseased star or with therapy
