Haemopoiesis Flashcards
Erythropoietin
Secreted by kidney, stimulates RBC production
Thrombopoietin
Produced by liver and kidney, regulates production of platelets
Haemopoietic stem cells
Capable of self-renewal, can be used in bone marrow transplants
Haemoglobin configurations
Oxyhaemoglobin - relaxed binding structure
Deoxyhaemoglobin - tight binding structure
Haemoglobin
Tetramer of 2 pairs of globin chains each with its own haem group
RBC cell membrane
Changes in the components of the cell membrane result in changes in RBC shape, causing them to become more fragile, spleen recognises abnormal cells and removes from circulation
Bilirubin
Broken down from haem, uncojugated bilirubin is transported in the blood bound to albumin, causes yellow appearance in jaundice
Stercobilin
bilirubin -> urobilinogen -> stercobilin
results in brown appearance of faeces
Urobilin
Urobilinogen absorbed into blood and transported to kidneys, oxidised to urobilin and excreted in urine giving yellow colour
G-CSF
A growth factor which: causes maturation of neutrophils, increases their production, enhances chemotaxis, enhances phagocytosis
Neutropenia consequences
Severe life-threatening bacterial/fungal infection
Causes of reduced production of neutrophils (neutropenia)
B12 deficiency, radiation, drugs, viral infection
Causes of increased removal or use of neutrophils (neutropenia)
Immune destruction by antibodies, sepsis (rapid migration to tissues, marrow unable to synthesise enough to maintain numbers)
Monocytes
Circulate for 1-3 days before differentiating into macrophages or dendritic cells
Causes of monocytosis
Bacterial infection, carcinoma
Eosinophils
Responsible for immune response against multicellular parasites, mediator of allergic responses, granules contain cytotoxic proteins
Common causes of eosinophilia
Allergies, skin disease, parasitic infection, drug hypersensitivity
Basophils
Least common, active in allergic reactions, large and dense granules containing histamine, granules stain deep blue to purple
Lymphocytes
B cells for humoral immunity
T cells for cellular immunity
Natural killer cells for cell mediated cytotoxicity
What is the reticuloendothelial system?
Part of the immune system and made up of monocytes in blood and a network of tissues which contain phagocytic cells
Role of reticuloendothelial system
Remove dead or damaged cells and identify and destroy foreign netizens in blood and tissues. The main organs are the spleen and liver.
Functions of spleen in adults
Removal of old/abnormal RBC by macrophages, rapidly mobilising RBC and platelets during bleeding (blood pooling),
Why might the spleen grow?
Expanding as infiltrated by cells (cancer cells of blood), portal hypertension in liver disease
Examination of spleen
Feel for spleen edge moving towards your hand
Hyposplenism
Lack of functioning splenic tissue, may be due to rupture, sickle cell disease, patients are at risk of sepsis from encapsulated bacteria
Using reference ranges for blood samples
Results outside the range (95%) are abnormal, normal range changes with: age, sex
What can be the the cause of abnormal haematology results
Specimen mix up, specimen delayed, wrong test
The full blood count
Uses K-EDTA anticoagulated, stops blood coagulation, the analyser is a closed system which is easy to maintain and able to cope with high numbers of samples
Spectophotometry
Amount of light absorbed by a sample proportional to the amount of absorbent compound within it, used to measure amount of haemoglobin, use calibration curve to determine sample conc
Flow cytometry
Single file line of cells pass through light beam, more scatter = bigger cell
Haematocrit
Proportion of blood that is made up of RBC, polycythemia is elevated haematocrit
Red cell count
Number of RBC in given volume of blood
Red cell distribution width
Variation in size of the RBC, helps to assess cause and timeline of anaemia
What happens if there is an abnormal full blood count result?
The sample is flagged for attention
Blood film
Smear of blood on a slide to be viewed under microscope
microcytic
small RBC
Macrocytic
Large RBC
Hypochromic
Pale, less Hb
Hyperchromic
Dense, more Hb
Spherocytosis
Spherical RBC
Elliptocytosis
Elliptical RBC
Acanthocytes
Spiculated (spiky) cells
Schistocytes
Red cell fragments
Target cells
Looks like bullseye
Blister cells
Have a blister, empty pocket at the edge, can be a sign of G6PD deficiency or haemolysis
Howell-Jolly bodies
DNA/nuclear fragments
Defects in haemoglobin synthesis
Iron deficiency can lead to not enough iron to make haem. Mutations in genes encoding globin proteins can also be a cause.
Reduced or dysfunctional erythropoesis
Kidney stops making erythropoietin, which usually binds to receptors on erythroblasts in bone cells and stimulates red cell production
