Haematology

• What is haematology


  Study of blood, blood forming organs and blood diseases
• Blood components


  45% erythrocytes

  <1% buffy coat (leukocytes and platelets)

  55% plasma
• what is blood?

  fluid produced in the bone marrow which is important for material transport around the body and maintaining homeostasis
• what is plasma?


  >90% water

  suspends cells and makes blood a fluid. contains many proteins and absorbs heat
• what is serum?


  liquid left when clotting factors e.g. fibrogen have been removed. more stable than serum
• what are average volumes of blood in a human?


  women: 5 L

  men: 5.5 L
• what are functions of blood?

  • gas transport
  • transport of nutrients
  • hormone transport + homeostasis
  • thermoregulation
  • osmosis
  • protection
  • detoxification
• what are properties of blood?

  • red in colour
  • 5L in volume
  • 7.4 pH
  • specific gravity of whole blood: 1.052-1.061
  • specific gravity of blood cells: 1.092-1.101
  • Specific gravity of plasma: 1.022-1.026
  • 5x more viscous than water
• what is haematocrit?


  packed cell volume, percentage of whole blood occupied by erythrocytes 42-45%
• what are common haematology techniques?

  • full blood count
  • blood films
  • erythrocyte sedimentation rate (ESR)
  • coagulation screen
  • immunophenotyping
  • haemoglobin variant techniques
  • molecular genetics
  • POCT (point of care testing)
• how is blood collected?

  venepuncture into tubes
• what are the coloured test tube meanings?


  Colours of caps:

  
• describe the cell surface of the erythrocytye


  Lipids, proteins and carbohydrates (49:43:8). surface antigens form blood groups
• what is the cluster of differentation?


  international nomneclature to identify cells, over 350

  e.g CD4 -> helper T cells
• what is the role of erythrocyte in blood?


  • Oxygen transport when associated to haemoglobin. anucleate so more room for haemoglobin.
  • 120 day lifespan, 6-8um diameter and niconcave. flexible due to the anucleate status and thin membrane
• what is haemoglobin?

  iron-containing protein that absorbs oxygen from areas of high-oxygen content (at lungs), and then releases it in areas where oxygen levels are low (tissues).

  Normally carried in blood inside RBCs. Approximately 640 million molecules of Hb in each RBC.
• How is aneamia or polycythaemia diagnosed?


  measure haematocrit
• what is the principle of Drabkin+ solution?


  Hb converted into stable cyanmethemoglobin (haemiglobincyanide), and absorbance in colour intensity of solution is measured in a spectrophotometer at 540nm
• What is the mcv?

  Mean cell volume
• what is the mchc?


  • mean cell haemoglobin volume
  • g/dL
  • reflects rbc staining intensity and amount of central pallor
• what is mch?

  • Mean cell haemoglobin
  • Measured in pg
  • Mass of haemoglobin
• what is rdw?


  • rbc distribution width
  • espresses degree of variation in rbc volume
• what are the uses of blood parameters?


  detect, diagnose, assess severity of and monitor treatment of anaemia and polycythaemia and other conditions affecting rbc
• Haematopoiesis


  The process of producing new blood cells, including red blood cells, white blood cells, and platelets, from stem cells in the bone marrow.
• Haematopoietic Stem Cell (HSC)


  The starting point of blood cell production, able to differentiate into all blood cell types, self-renewing.
• Progenitor Cells


  Immature cells that have begun to differentiate into specific blood cell lineages, produced from HSCs.
• Myeloid Progenitor Cells


  Gives rise to red blood cells, platelets, and granulocytes
• HSC

  Quiescent State: HSCs spend most of their time in a dormant state, conserving energy and resources.

  - Activation: HSCs are triggered to proliferate and differentiate by growth factors, such as Stem Cell Factor (SCF).

  - Self-Renewal: HSCs have the ability to self-renew, maintaining the pool of stem cells and ensuring continuous blood cell production.
• Progenitor cells


  • Immature State: Progenitor cells are not yet fully developed and are sensitive to their microenvironment.
  •  Differentiation: Progenitor cells undergo differentiation, producing specific blood cell types.
• Myeloid progenitor cells


  CMP: The CMP is the earliest committed progenitor cell, giving rise to red blood cells, platelets, and granulocytes.
• EPCs

  Erythroid Progenitor Cells (EPCs):

  - Epo-Dependent: EPCs are dependent on erythropoietin (EPO) for survival and differentiation.

  - Globin Gene Expression: EPCs express haemoglobingenes, producing adult haemoglobin (HbA).
• GPCs

  Granulocyte Progenitor Cells (GPCs):

  - Colony-Stimulating Factors (CSFs): GPCs respond to CSFs for differentiation and maturation.

  - Differentiation: GPCs differentiate into neutrophils, eosinophils, and basophils.
• Maturation

  Maturation:

  - Bone Marrow Development: Mature blood cells develop in the bone marrow, where they receive necessary signals and differentiation cues.

  - Release into Circulation: Mature blood cells are released into the circulation, where they function and interact with the immune system.
• Where does haemopoiesis occur?


  In adults, exclusively in red bone masrrow: skull, sternum, ileum and long bones

  In neonates, all bone marrow is red and haemopoietic. Can also occur in some organs such as kidney and liver.
• Where does ontogeny begin in the embryo?

  Haemogenic endothelium of the aorta-gonad mesonephron
• What primitive stem cells appear by the third week after fertilization?

  Haemocytoblasts
• What happens to stem cells after approximately 4-6 weeks of ontogeny?

  They migrate to the liver and spleen
• What becomes the dominant sites of blood cell production after stem cells migrate?

  The liver and spleen
• Between which months does the liver become the major site of blood cell production?

  1. 7 months
• When do stem cells migrate to the bone marrow?

  During the 5-9 months of gestation