Haem 1 - Physiology of Blood cells and haematological terminology Flashcards
Explain the origin of blood cells
ALL blood cells (all types) originate in bone marrow
- They are derived from multipotent haemopoietic stem cells which give rise to lymphoid stem cells and myeloid stem cells
What can arise from myeloid stem cell precursor
- Granulocyte-monocyte
- Erythroid
- Megakaryocyte
What can arise from lymphoid stem cell
T cell/ B cell/ NK cell
What is an essential characteristic of a stem cell
It can self renew and produce mature progeny - 2 cells formed, 1 stem cell and 1 differentiable cell
Explain how RBCs arise
Myeloid stem cell precursor gives rise to pro erythroblast (has nuclei) –> which then gives rise to (early/intermediate/late) erythroblast —-> erythrocytes (anuclei)
Erythropoiesis (producing RBC) requires erythropoietin. Where is erythropoietin synthesised in response to what
Erythropoietin synthesised in kidney in response to hypoxia (/anaemia)
In the juxtatubular interstitial cell of the kidney (90%)
(Also 10% erythropoietin in the liver - hepatocyte and interstitial cells)
Ultimately, how are RBCs destroyed
Phagocytic cells of spleen
How are white cells formed
Multipotent haemopoietic stem cell - gives rise to myeloblast –> in turn gives rise to granulocytes and monocytes
It requires cytokines (G-CSF, M-CSF, GM-CSF) and various interleukins
How long do neutrophil granulocytes survive in circulation before migrating to tissues?
7-10 hours
What is the main function of an eosinophil
eosinophils also arise from myeloblasts
Defence against parasitic infection
Eosinophils spend less time in circulation than neutrophil
Myeloblasts can also give rise to basophils. What are their main function
Allergic responses
Myeloblasts can also give rise to monocyte precursors and then monocytes. How long do monocytes spend in circulation?
Several days
What do monocytes do
They migrate into tissues - where they develop into macrophages and other specialised cells - have a phagocytic and scavenging function
Macrophages also store and release iron
How do platelets arise and how long do they spend in the circulation
Haemopoietic stem cells - give rise to megakaryocytes –> platelets
10 days in circulation
What 2 roles do platelets have
- Primary haemostasis
2. They contribute phospholipid - promoting blood coagulation
What do lymphoid stem cells give rise to, and what do these differentiated cells do
Lymphoid stem cell –> T/B/NK cells
Lymphocytes recirculate to lymph nodes and other tissues - then go back to blood stream
Lymphocytes have variable intravascular lifespan
What is anisocytosis?
red cells show more variation in size than normal
What is poikilocytosis?
Poikilocytosis - red cells show more variation in shape than normal
“Pointy = shape”
What is microcytosis and what is macrocytosis
Microcytosis - cells smaller than normal
Macrocytosis = cells larger than normal
What are the specific types of macrocytes (Red Cells larger than normal)
- Round macrocytes
- Oval macrocytes
- Polychromatic macrocytes - 2 colours, blue tinge on the outside - indicates a young cell, newly released from bone marrow
Define microcytic, normocytic, macrocytic
Microcytic - red cells smaller than normal or anaemia with small red cells
Normocytic - red cells normal size or anaemia with normal sized red cells
Macrocytic - red cells larger than normal or anaemia with large red cells
Normal red cells have a third of the diameter that is pale - why?
The centre has less Hb so it is paler (due to disk shape)
What is hypochromia?
What is it often associated with?
Hypochromia = cell have larger area of central pallor than normal - as as result of lower Hb conc/content and flatter cell
Hypochromia often associated with microcytosis
What is hyperchromia
Hyperchromia = cells lack central pallor - may occur because cells are thicker than normal or abnormal shape
Name 2 important hyper chromatic cell types
Hyperchromia has many causes - because many abnormally shaped cells lack central thinner area
- Spherocytes - spherical in shape (and lack central pallor) - as a result of loss of cell membrane but not cytoplasm, the cell must adopt round shape to include cytoplasm
(Can be inherited - “hereditary spherocytosis”)
- Irregularly contracted cells
Irregularly contracted cells are a form of hyperchromatic cell - what are they the result of
Usually caused by oxidant damage to cell membrane and Hb
What does polychromasia indicate ?
Polychromasia = increased blue tinge to cytoplasm of red cell
Indicates a young cell
How can we detect young cells?
Do a reticulocyte stain - expose red cells to new methylene blue - precipitates as a reticulum (network)
only 1-2% reticulocytes
(Also polychromasia indicates a young cell - but reticulocyte identification more reliable)
What are the various shapes that poikilocytes may come in?
- Spherocytes
- Irregularly contracted cells
- Sickle cells
- Target cells
- Elliptocytes
- Fragments
Describe target cells (poikilocyte type)
Target cells = cells with accumulation of Hb in centre (where there should be pallor)
Target cells occur in obstructive jaundice, liver disease, haemoglobinopahies and hyposplenism
Elliptocytes are elliptical in shape. When do they occur
- In hereditary elliptocytosis
2. Iron deficiency
Sickle cell - what are the causes
Sickle cell results from polymerisation of Hb S (when present in high enough conc)
Usually we have Hb A
What are fragments/”schistocytes”
Small pieces of red cells - indicate red cell has fragmented
Describe rouleaux formation
Rouleaux = stack of red cells - as a result of alteration in plasma proteins
Describe agglutinates
Red cell agglutinates = irregular clumps (whereas rouleaux = tidy stacks)
- They result from antibody on surface of cells
Describe Howell-Jolly body
Howell-Jolly body = nuclear remnant in RBC - indicates lack of splenic function
What are the terms associated with white cells / neutrophils / lymphocytes / eosinophils
- Leucocytosis = too many white cells
- Leucopenia = too few white ells
- Neutrophilia/penia = too many/too few neutrophils
- Lymphocytosis = too many lymphocytes
- Eosinophilia = too many eosinophils
Thrombo =?
Erythro =?
Reticulo = ?
Lympho = ?
Thrombo = platelet
Erythro = RBC
Reticulocytosis = Reticulocytes (young RBCs)
Lymphopenia = lack of lymphocytosis
Describe the term “atypical lymphocyte”
Atypical lymphocyte = abnormal lymphocyte
Often used to describe abnormal cells in glandular fever (/”infectious mononucleosis”)
What is left shift
Increase in non-segmented neutrophils (or neutrophil precursors present in blood) - e.g. band forms, myelocytes or even promyelocytes
It is a sign of infection or inflammation
What is toxic granulation
Heavy granulation of neutrophils - may arise from infection, inflammation and tissue necrosis
(it is also a normal feature in pregnancy)
What is a hypersegmented neutrophil
Neutrophil hyper segmentation = increase in average number of neutrophil lobes/segments
Usually results from lack of Vit B12 or folic acid
