lecture 1 - the blood count Flashcards
What is the morphology of RBCs in a normal blood film?
Uniform size, central pale zone occupies 1/3 red cell diameter.
What stain is typically used in a blood film?
Romanowsky stain
What is the morphology of platelets in a stained normal blood film?
Pale purple cytoplasm, central granules
What RBC values are measured in a blood count?
Haemoglobin, mean cell volume, mean cell Hb, Haematocrit, Red cell count, mean cell Hb conc.
What are the 2 most important RBC parameters in a blood count?
Haemoglobin (g/L), mean cell volume (fL)
What does the mean cell volume show about RBCs?
Their size, and therefore how much Hb they are carrying.
What 3 values regarding RBCs are measured in a blood count, and are then used to calculate other parameters?
Hb concentration, mean cell volume, red cell count
What is the normal range for MCV (mean cell volume in fL) for adult females?
80-99 (same as males)
What is the normal range for MCV (mean cell volume in fL) for adult males?
80-90 (same as females)
What is the biomedical definition of Anaemia?
Low haemoglobin levels - and thus a reduced ability to transport oxygen in blood
What is the WHO definition of anaemia for males, in terms of Hb concentration (g/L)?
Hb < 130g/L
What are the 3 types of anaemia, based on morphological pattern/cell size?
microcytic (small cells), normocytic (normal cells), macrocytic (large cells)
What terms are used to describe low, normal and high levels of Hb in a RBC?
hypochromic (low Hb), normochromic (normal Hb), hyperchromic (high Hb)
What is observed in a blood film displaying normocytic anaemia?
Normal red cells, but fewer of them
What is observed in a blood film displaying microcytic anaemia?
Small under-filled pale red cells containing less Hb
What is observed in a blood film displaying macrocytic anaemia?
Large red cells
What type of anaemia is caused by iron deficiency?
microcytic anaemia
What are the features of microcytic anaemia in a blood count?
Low Hb, low MCV (mean cell volume)
What are the causes of normocytic anaemia?
haemodilution, renal failure, bone marrow failure, anaemia of inflammation
What type of anaemia does haemodilution cause, and why?
Normocytic - after acute blood loss the blood can be diluted before RBCs can be generated.
What type of anaemia does renal failure often cause, and why?
Normocytic anaemia - insufficient erythropoietin (EPO) production leads to lower RBC production
What type of anaemia does inflammation cause, and why?
Normocytic, though microcytic when severe - reduced RBC production due to reduced availability of iron to prevent bacterial colonisation.
What are the features of normocytic anaemia in a blood count?
Low Hb concentration, but normal mean cell volume
What is the most common cause of macrocytic anaemias?
Liver disease,folic acid & vitamin B12 deficiency
What specific type of anaemia does folic acid or Vitamin B12 deficiency cause?
Megaloblastic anaemia
What is megaloblastic anaemia?
When the bone marrow produces large, irregular, immature red blood cells (megaloblasts)
What are the features across a blood count, of macrocytic anaemia?
Pancytopenia - reduction in Hb, platelets and neutrophils, high mean cell volume, and mean cell haemoglobin
What is the name of the process in which blood cells are made?
Haematopoiesis
Where does haematopoiesis occur?
Bone marrow
Where is the bone marrow in which haematopoiesis occurs in adults?
mainly the axial skeleton - skull, vertebrae, ribs, sternum, pelvis
Where is the bone marrow in which haematopoiesis occurs in children?
axial skeleton and long bones
Where does haematopoiesis occur in fetuses?
The liver and spleen, minimal in the bone marrow
What is the difference between totipotent and pluripotent stem cells?
Totipotent can develop into embryonic or placental tissues, while pluripotent can develop into all embryonic lineages
What is the name for blood stem cells in the marrow that can develop into all types of blood cell?
Haematopoietic stem cells
What are the 2 committed stem cells that haematopoietic stem cells can directly differentiate into, and what lineages do they begin?
Myeloid stem cells (meyloid lineage), lymphoid stem cells (lymphoid lineage)
What cells are in the myeloid lineage?
erythrocytes (RBCs), platelets, some white blood cells (granulocytes, monocytes/macrophages),
What cells are the lymphoid lineage?
B-cells, T-cells, Natural Killer Cells
What is the role of cytokine signals in haematopoiesis?
Regulation - induce growth & differentiation
Where are cytokine signals that regulate haematopoiesis produced?
Peripheral tissues and cells of bone marrow
What is the role of marrow stromal cells in haematopoiesis regulation?
regulatory signals act on marrow stromal cells.
What is erythropoiesis?
Red blood cell (erythrocyte) production
