TOB S10 - Blood Cells and Haemopoiesis Flashcards
What are the two stages of haemopoiesis?
Proliferation
Differentiation
Give a brief description of haemopoietic Proliferation
Starting with a stem cell the cell divides in two
One replaces the original stem cell
One will differentiate
Describe the process of haemopoietic differentiation
Haemopoietic progenitor cell will differentiate to either:
- A lymphoid blast which will go on to form immunoresponse cells
- A myeloid blast which will go on to form Erythrocytes, platelets or White blood cells
The progenitor will then differentiate into a certain cell type under the influence of particular cytokines
What cytokine will cause a myeloid blast to differentiate into an erythrocyte and which will cause it to differentiate into a platelet?
Erythrocyte = Erythropoietin
Platelet = Thrombopoietin
What controls rate of erythropoiesis?
Partial pressure of O2
Fall in pO2 will stimulate erythropoietin release from kidney
This stimulates maturation and release of red cells from the marrow
How many RBCs, granulocytes and platelets are produced per day?
RBCs = 2.5 billion/kg/day
Platelets = 2.5 billion/kg/day
Granulocytes = 1.0 billion/kg/day
Where are RBCs, WBCs and platelets produced in the body and how does this change as we age?
Produced in the bone marrow
Widespread throughout the bone marrow in infants
More limited distribution in adulthood:
Pelvis, Sternum, Skull, Ribs, Vertebrae
What are peripheral blood levels of:
Hb
RBCs
WBCs
Platelets
Hb = 130-160g/L
RBCs = 4.4-5.5x10^12/L
WBCs = 7-11x1^9/L
Platelets = 150-400x10^9/L
What are the main functions of a RBC?
To deliver oxygen to tissues and deliver carbon dioxide to the lungs
Carry haemoglobin
Maintain haemoglobin in its reduced state (ferrous)
Maintain osmotic equilibrium
Generate ATP
Describe the form of a RBC
How is this useful?
Biconcave flexible disk
8um in diameter
Facilitates passage through microvasculature which has a minimum diameter of 3.5um
How is Haemoglobin catabolised?
Broken down into constituent parts, Fe2+ is recycled
Haem is converted to bilirubin and conjugated in the liver
Liver releases conjugated bilirubin into the gall bladder/small intestine and it is changed into a variety of pigments, the most important of which are stercobilin and urobilinogen
Stercobilin is excreted in the faeces
Urobilinogen may be passed back into the blood and excreted by the kidneys.
How are the platelets produced?
Megakaryocytes produce platelets
Platelets bud off from the cytoplasm
Describe the features of platelet structure relevant to the clotting process
Phospholipid membrane w/glycoprotein receptors for clotting factors and platelet adhesion
alpha-granules in the cytoplasm produce the glycoproteins
Dense bodies in the cytoplasm produce 5-HT, ADP, catecholamines and calcium for platelet aggregation
How are platelets involved in a blood clot?
Platelets are activated leading to adhesion to the damaged section of membrane via Von Willebrand’s factor
The then aggregate with other platelets
The Fibrin mesh of a blood clot traps platelets (as well as red cells)
Also involved in the clotting cascade, interact with various clotting factors via their phospholipid membrane (particularly factor III, which activates prothrombin into thrombin, resulting in fibrin production)
5-HT from the Dense granules constricts blood vessel
What are the effects of granulocyte - colony stimulating hormone on Neutrophils?
Increases production
Enhances chemotaxis - Attraction of the neutrophil to site of infection
Enhances phagocytosis and killing of pathogens
Give a basic outline of neutrophil function
What is the average survival time of a neutrophil?
Are inactive in the bloodstream
Migrate into infected tissues
Neutrophils phagocytose invader
Destroys the pathogen using hypochlorous acid
Gross accumulation visible as pus
Average survival time of 10 hours
What is the function of Monocytes?
Migrate to tissue and become active macrophages (inactive in bloodstream)
Respond to inflammation and antigenic stimuli
They phagocytose pathogens which are degraded with lysosomal enzymes
Can interact with T-cells
What is the Reticulo-endothelial system?
What is it’s function?
What are the main organs of the RES?
Part of the immune system comprising of:
Monocytes Macrophages Kupfer Cells Microglia Tissue Histiocytes
Cells of the RES identify and mount an appropriate immune response to foreign antigens
Main organs are:
Spleen
Liver
Lymph Nodes
How long do Eosinophils remain in the circulation and what is their total lifespan?
3-8 hours in circulation
8-12 days total lifespan
What is the function of Eosinophils?
Phagocytosis of antibody-antigen complex
Mediate hypersensitivity reactions E.g. Asthma, skin inflammation
Can release cytotoxic enzymes to damage larger particles
What is the function of Basophils?
Active in allergic reactions using heparin and histamine
What s contained in the dense granules in the cytoplasm of Basophils?
Histamine
Heparin
Hyaluronic acid
5-HT
Where do Lymphocytes originate from and what are the 3 types?
Originate from bone marrow
B-cells
T-cells
Natural killer cells
What is the function of B-cells?
Express antigen specific Immunoglobulin (antibody)
Each B-cell only expresses a certain Ig
They interact with T-cells forming plasmablast or memory cells
