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Questions and Answers
What is the primary site of haematopoiesis after birth?
What is the primary site of haematopoiesis after birth?
Which of the following is NOT a type of haematopoiesis mentioned?
Which of the following is NOT a type of haematopoiesis mentioned?
Which growth factor is specifically mentioned as impacting erythropoiesis?
Which growth factor is specifically mentioned as impacting erythropoiesis?
Haematopoietic stem cells have the ability to do which of the following?
Haematopoietic stem cells have the ability to do which of the following?
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What does a diagnosis of acute lymphoblastic leukaemia (ALL) primarily indicate?
What does a diagnosis of acute lymphoblastic leukaemia (ALL) primarily indicate?
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Which lineage gives rise to all other leukocytes, erythrocytes, and platelets?
Which lineage gives rise to all other leukocytes, erythrocytes, and platelets?
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What type of cells do committed progenitor cells differentiate into?
What type of cells do committed progenitor cells differentiate into?
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What is a common characteristic of patients with Acute Lymphoblastic Leukemia (ALL)?
What is a common characteristic of patients with Acute Lymphoblastic Leukemia (ALL)?
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Which component is NOT necessary for erythropoiesis?
Which component is NOT necessary for erythropoiesis?
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What primarily stimulates the secretion of erythropoietin (EPO)?
What primarily stimulates the secretion of erythropoietin (EPO)?
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What is the immediate precursor cell to a mature erythrocyte?
What is the immediate precursor cell to a mature erythrocyte?
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In Chronic Myeloid Leukemia (CML), what is the common age for diagnosis?
In Chronic Myeloid Leukemia (CML), what is the common age for diagnosis?
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What is a characteristic feature of the white blood cells in the early stages of Chronic Myeloid Leukaemia?
What is a characteristic feature of the white blood cells in the early stages of Chronic Myeloid Leukaemia?
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During which stage of erythropoiesis does the nucleus degenerate?
During which stage of erythropoiesis does the nucleus degenerate?
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Which of the following is NOT true about erythrocyte lifespan?
Which of the following is NOT true about erythrocyte lifespan?
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Which factor is a key player in stimulating erythropoiesis by mediating the response to hypoxia?
Which factor is a key player in stimulating erythropoiesis by mediating the response to hypoxia?
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What is the primary role of iron in the human body?
What is the primary role of iron in the human body?
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Which of the following indicators is most sensitive for early iron deficiency?
Which of the following indicators is most sensitive for early iron deficiency?
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Which condition is characterized by the premature rupture of erythrocytes?
Which condition is characterized by the premature rupture of erythrocytes?
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What deficiency can lead to macrocytic erythrocytes due to impaired DNA synthesis?
What deficiency can lead to macrocytic erythrocytes due to impaired DNA synthesis?
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Which condition is commonly associated with the autoimmune destruction of intrinsic factor?
Which condition is commonly associated with the autoimmune destruction of intrinsic factor?
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What is the earliest evidence of haemochromatosis?
What is the earliest evidence of haemochromatosis?
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What is the primary defect in polycythemia vera?
What is the primary defect in polycythemia vera?
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Which factor can lead to normoblast apoptosis when deficient?
Which factor can lead to normoblast apoptosis when deficient?
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What condition is associated with joint pain, fatigue, and liver disease due to iron overload?
What condition is associated with joint pain, fatigue, and liver disease due to iron overload?
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Study Notes
Haematology Lecture 2: Haematopoiesis & Blood Indices
- Haematopoiesis is the formation of blood cells
- In the foetus, haematopoiesis occurs in the liver, spleen, and blood
- After birth, haematopoiesis mainly occurs in red bone marrow
- Haematopoiesis requires interaction with stromal cells in the bone marrow
- Development and differentiation depend on specific growth factors and cytokines
Learning Objectives
- The pathways of haematopoiesis
- Some disorders of haematopoiesis
- Erythropoiesis
- Factors influencing erythropoiesis
- Some blood disorders
- Haematology tests
- Calculated blood indices
Haematopoietic Stem Cells
- Self-renewing, multipotent stem cells residing in bone marrow
- Respond to haematopoietic growth factors (e.g., erythropoietin, colony-stimulating factors, interleukins)
- Capable of self-renewal and differentiation into committed progenitor cells
- Committed progenitors belong to myeloid or lymphoid lineages
- Lymphoid lineage gives rise to lymphocytes
- Myeloid lineage gives rise to other leukocytes, erythrocytes, and platelets
Acute Lymphoblastic Leukaemia (ALL)
- Diagnosis based on very high numbers of abnormal early-stage lymphoid precursor cells (lymphoblasts)
- Patients often have reduced neutrophils and decreased myeloid cells due to bone marrow overcrowding
- Diagnosis requires 20% bone marrow lymphoblasts
Chronic Myeloid Leukaemia
- Extremely high white blood cell (WBC) count and platelet count
- Mature white blood cells and normal red blood cells indicate early stage of differentiation
- Cancer arises during a later stage (chronic)
- Increased cells originate from the myeloid lineage
- Median age of diagnosis is 56, often asymptomatic
Erythropoiesis
- Erythrocytes (red blood cells) have a lifespan of 120 days
- 2.5 million erythrocytes are replaced every second
- Requires iron, vitamin B12, and folic acid
- Stimulated primarily by erythropoietin (EPO) produced by the kidneys in response to need
- EPO circulates in plasma with a 7-8-hour half-life
- EPO acts by binding to receptors on pronormoblasts in bone marrow
Iron
- Essential for haemoglobin synthesis and function
- Absorbed from the diet in the small intestine (only 1mg/day of the 15mg required is absorbed to replace lost iron)
- Remainder recycled from dead red blood cells
- 65% of body’s iron is in haemoglobin
- Stored as ferritin (a complex of protein and Fe²⁺)
- Free iron is transported in the blood as Fe³⁺ bound to transferrin
Iron-Deficiency Anaemia
- The most common type of anaemia
- Findings include low ferritin, possible low red blood cell count, low haemoglobin, low haematocrit, and microcytic/hypochromic erythrocytes
- Erythrocytes may be microcytic (low mean corpuscular volume (MCV))
- Erythrocytes can be hypochromic (low mean corpuscular haemoglobin (MCH) and mean corpuscular haemoglobin concentration (MCHC))
- Target cells and pencil cells may be observed
Folic Acid & Vitamin B12
- Essential for DNA synthesis
- Deficiency impairs DNA synthesis, causing normoblast apoptosis
- Deficiency resulting in larger, more immature reticulocytes (macrocytic erythrocytes, megaloblastic anaemia)
- Asynchronous maturation between cytoplasm and nucleus
- Vitamin B12 binds to intrinsic factor for absorption in the ileum
- Deficiency can be caused by dietary restrictions (strict vegan diet), age-related absorption problems, or autoimmune diseases (pernicious anaemia)
Other Blood Disorders
- Categories of anaemia: haemorrhagic (sudden or persistent blood loss), haemolytic (premature erythrocyte rupture), aplastic (bone marrow destruction or inhibition), etc
- Other blood disorders include leukaemia, leukopenia, various anaemias, haemochromatosis, and polycythemia
Haemochromatosis
- Iron overload, causing abdominal pain, weakness, fatigue, joint pain, liver disease, and endocrine/cardiac abnormalities
- High transferrin saturation is an early indication of the disease
- Commonly due to mutation in the HFE gene
- Autosomal recessive condition
- High prevalence in Ireland (1 in 5 carry the gene, 1 in 83 have both genes)
- Treatment involves regular phlebotomies
Polycythemia Vera
- Myeloproliferative disorder of red blood cells with overproduction of red blood cells
- Prevalence of 22 cases per 100,000
- Male-to-female ratio: 2:1
- Caused by an acquired genetic mutation leading to EPO oversensitivity
- Increased risk of thrombotic events (e.g., stroke, deep vein thrombosis)
Common Haematological Tests
- Complete blood count (CBC)
- Red blood cell (RBC) count
- Total/differential white blood cell (WBC) count
- Platelet count
- Haematocrit (packed cell volume)
- Haemoglobin (Hb%)
- Iron profile
Calculated Blood Indices
- Mean corpuscular volume (MCV) - average volume of red blood cells (normal range 80-100 fL)
- Mean corpuscular haemoglobin (MCH) - average haemoglobin per red blood cell (normal range 27-31 pg/cell)
- Mean corpuscular haemoglobin concentration (MCHC) - average concentration of haemoglobin per red blood cell (normal range 32-36 g/dL or 32-36%)
Summary of Main Points
- All blood cells originate from haematopoietic stem cells in bone marrow (myeloid and lymphoid lineages)
- Erythropoiesis, leukopoiesis, thrombopoiesis
- Rate of cell production equals rate of destruction
- Blood disorders include leukaemia, leukopenia, various anaemias, haemochromatosis, and polycythemia
- Blood tests and indices are used for diagnosis and monitoring. Some are directly measured while others are calculated.
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Description
Explore the intricacies of haematopoiesis and blood indices in this insightful quiz. Learn about the formation of blood cells, the role of haematopoietic stem cells, and key growth factors influencing erythropoiesis. Test your knowledge on associated blood disorders and haematology tests.
