Flashcards in Introduction to haematology Deck (46)
What is haematopoiesis?
- The physiological developmental process that gives rise to the cellular components of blood
- A single multipotent haemopoietic stem cell can divide and differentiate to form different cell lineages that will populate the blood
What is a haemopoietic stem cell?
- Differentiation potential for all lineages
- High proliferative potential
- Long term activity throughout the lifespan of the individual
- Self renewal
What is symmetric self-renewal?
Increase stem cell pool – NO generation of differentiated progeny
What is asymmetric self-renewal?
Maintain stem cell pool – generation of differentiate progeny.
What is lack of self-renewal?
Deplete stem cell pool – generation of ONLY differentiated progeny
Maintain stem cell pool – NO differentiated progeny
What are the two haemopoietic lineages?
At what point in human development does heamopoiesis start?
Where does heamopoiesis start?
In the aorta-gonado-mesonephros region,
expands rapidly at day 35, then disappear at day 40.
Why does the aorta-gonado-mesonephros region disappear?
This disappearance correlates with the migration of these hematopoietic stem cells to the foetal liver, which becomes the subsequent site of haemopoiesis.
What are the features of erythrocytes?
Bi-concave discs, 7.5 µM diameter
What is the lifespan of an erythrocyte?
What is anaemia?
What is polycythaemia?
Abnormally raised erythrocytes
What is relative polycythaemia?
Plasma volume is reduced so erythrocytes appear raised
What are granulocytes?
Have cytoplasmic granules (neutrophils, eosinophils, basophils)
What is the function of neutrophils?
What is neutrophilia?
Increased numbers of neutrophils
Why might neutrophil levels be increased?
Bacterial infection and inflammation
What is the lifespan of neutrophils?
A few hours
What is neutropenia?
Decreased numbers of neutrophils
Why would eosinophil levels be increased?
- Parasitic infection
Why might basophil levels be increased?
What are monocytes?
- Phagocytic & antigen-presenting cells
- Migrate to tissues & are then identified as “macrophages” or “histiocytes”
e.g. Kupffer cells in liver
e.g. Langerhans cells in skin
What is monocytosis and why might it occur?
Increased numbers of monocytes. Can happen in TB.
What is the function of NK cells?
- Recognise “non-self”
e.g. Cells, viruses
- Large granular lymphocytes
What are B-lymphocytes?
- Adaptive immune system
- rearrange the immunoglobulin genes to enable antigen specific antibody production
- humoral immunity
What are T-lymphocytes?
- Adaptive immune system
- rearrange the T-cell antigen receptor
- cell-mediated immunity
- target specific cytotoxicity
- Interact with B cells, macrophages
- Regulate immune responses
What is lymphocytosis and why might it occur?
Increased numbers of lymphocytes.
e.g. atypical lymphocytes of glandular fever (infectious mononucleosis)
e.g. Chronic lymphocytic leukaemia
What is lymphopenia and why might it occur?
Decreased numbers of lymphocytes.
e.g. post bone marrow transplant
What is plasmocytosis and why might it occur?
Increased numbers of plasma cells
e.g. infection, myeloma
What are platelets derived from?
Bone marrow megakaryocytes
What measures are included in a full blood count?
- Haemoglobin concentration
- Red cell parameters
- MCV (mean cell volume)
- MCH (mean cell Hb)
- White Cell Count (WCC)
- Platelet Count
What measures are included in a coagulation test?
- Prothrombin Time
- Activated Partial Thromboplastin Time
- Thrombin Time
How is a bone marrow aspirate & trephine performed?
Under local anaesthetic, liquid marrow is aspirated from the posterior iliac crest of the pelvis and a trephine core biopsy is then taken with a hollow needle.
How is a reference range established?
- Define the reference population
- Reference population should be relevant to the test population
- Consider if separate ranges are required for adults versus children, men versus women, and so forth.
- Determine the expected range of interindividual variation
What is a reference range?
The set of values for a given test that incorporates 95% of the normal population
What percentage of results fall within the reference range?
What is sensitivity?
- The proportion of abnormal results correctly classified by the test.
- Expresses the ability to detect a true abnormality
What is specificity?
- The proportion of normal results correctly classified by the test
- Expresses the ability to exclude an abnormal result in a healthy person
In what situation might an abnormal lymphocyte count be expected?
- Post-splenectomy, mild lymphocytosis
- 3 months post-bone marrow transplant lymphopenia
What is microcytic anaemia?
What are the causes of microcytic anaemia?
- Iron deficiency
- Anaemia of chronic disease (some)
- Lead poisonng
- Sideroblastic anaemia (some cases)
What is normocytic anaemia?
MCV 80-95 fl & MCH ≥ 27 pg
What are the causes of normocytic anaemia?
- Many haemolytic anaemias
- Anaemia of chronic disease (some cases)
- After acute blood loss
- Renal disease
- Mixed deficiencies
- Bone marrow failure (e.g. post-chemotherapy, infitration by carcinoma etc)
What is macrocytic anaemia?
MCV >95 fl