3.1 RBCs Flashcards
What is haemopoiesis?
the formation and development of blood cells
What is haemopoiesis regulated by?
a number of:
- genes
- transcription factors
- the microenvironment
- growth factors
What can happen if haemopoiesis regulation is disrupted?
The balance between proliferation and differentiation of the HSC may be disturbed, leading to leukaemia or bone marrow failure
Where do all blood cells originate and from what cell?
bone marrow from pluripotent haemopoietic stem cells (HSCs) throughout life
Erythrocyte life span and function
120 days
Transports oxygen
Platelet life span and function
10 days
Haemostasis
Neutrophil life span and function
7-10 hours
Phagocytosis and killing micro organisms
Monocytes lifespan and function
A few days
Phagocytosis and killing micro organisms
Eosinophil lifespan and function
A little less than neutrophils (less than 7-10 hours)
Defence against parasitic infection
Lymphocyte lifespan and function
Very variable
Humoral and cellular immunity
How many blood cells does the average person produce each day?
500 billion
What are the 2 essential characteristics of HSCs?
1) Self-renew: some daughter cells remain as HSCs so the pool of HSCs is not depleted
2) Differentiate to mature progeny: i.e. myeloid and lymphoid progenitor cells that follow a differentiation pathway and can’t renew themselves as they’re committed down that pathway
Sites of haemopoiesis in foetuses?
YOLK SAC - LIVER - BONE MARROW
In embryonic development, HSCs are derived from the mesoderm layer in the yolk sac
Platelet precursors, macrophages and primitive RBCs are initially formed in the vasculature of the sac before the liver takes over as the main site of haemopoiesis at 6-8 weeks of gestation and is then the primary source of blood in the foetus
Then, the bone marrow starts developing haemopoietic activity around 10 weeks into gestation
Sites of haemopoiesis in adults
in adults haemopoiesis mainly occurs in the bone marrow- especially in the pelvis, femur and sternum
What other cells/structures are distributed with HSCs in the bone marrow?
HSCs interact with:
- HSC progenitor cells
- mesenchymal stem cells
- endothelial cells
- vasculature
What is a growth factor?
Glycoprotein hormones that bind to cell surface receptors that regulate proliferation + differentiation of HSCs and regulate function of mature blood cells
Erythropoiesis growth factor?
Erythropoietin (produces red blood cells)
Granulocyte and monocyte production growth factors?
G-CSF, G-M CSF, cytokines e.g. interleukins
Megakaryocytopoiesis and platelet production growth factor?
THROMBOPOIETIN (TPO)
Erythropoiesis
What is the overall progression of RBC development cell-wise?
The common myeloid progenitor gives rise to a proerythroblast which gives rise to erythroblast and then erythrocytes (RBC)
Erythroblasts have a nucleus to start with but lose it before becoming erythrocytes
What are polychromatic erythrocytes?
Have a blue tinge due to high RNA content- lose ribosomes after a few days and become mature erythrocytes
What 4 things are needed for erythropoiesis?
- Iron
- Folate/ folic acid
- Vitamin B12
- Erythropoietin- regulating growth factor
What does it mean if we see nucleated RBCs in blood?
There’s a high demand for bone marrow to produce RBCs so immature RBCs are being prematurely released into circulation
Where and how is erythropoietin made and how does it work?
Made mainly in the kidney in response to hypoxia ( when not enough o2 available )
It interacts with erythropoietin receptors on red cell progenitor membranes which stimulates bone marrow to increase production of RBCs
