Physiology Flashcards
What is haematopoiesis?
The production of blood cells
What are mature blood cells produced from?
Precursor stem cells
What are stem cells?
Cells from the mesoderm that can self-renew, proliferate and differentiate into any type of blood cell
Once a stem cell has started down a lineage pathway can it go back?
No
What are the sites of haematopoiesis at birth?
Mainly bone marrow
Plus the liver and spleen when needed
What are the sites of haematopoiesis in adulthood?
Only the axial skeleton - skull, ribs, sternum, pelvis, proximal ends of femur
What are the types precursor cell that stem cells can differentiate into?
Common myeloid precursor
Common lymphoid precursor
What do common lymphoid precursors differentiate into?
B cells, T cells and NK cells
What do common myeloid precursors differentiate into?
Megakaryocyte/erythroid precursor - then platelets/RBC
Granulocyte/macrophage precursor - then granulocytes/macrophage
What are the granulocytes?
Basophils, eosinophils, neutrophils
What is the main function of red blood cells?
Carry oxygen
What is the main function of platelets?
Stop bleeding
What is the main function of white blood cells?
Fight infection
What is erythropoiesis?
The production of RBCs
What stimulates erythropoiesis?
Reduced oxygen carrying capacity in the blood stimulates erythropoietin production and release from the kidneys
What are reticulocytes?
The immediate precursors to red blood cells
What are the features of reticulocytes?
No nucleus
Larger than RBCs
Contain RNA - making them polychromatic
What are the features of mature RBCs?
Biconcave shape
No nucleus
No mitochondria
What is the consequence for RBCs having no nucleus?
Can’t divide or self-renew
What is the energy source for RBCs?
Glycolysis
What is the lifespan of mature RBCs?
120 days
Which organs get rid of RBCs at the end of their lifespan?
Spleen
Liver
What is the structure of haemoglobin?
4 globin chains (2 alpha, 2 beta in HbA - adult)
Haem group made of Fe2+ and a porphyrin ring
Why does the haem group have Fe2+ not Fe3+?
Oxygen does not bind to Fe3+
What is the process of red cell destruction?
Aged red cells are taken up by macrophages
Red cell contents are recycled
Globing chains are recycled to amino acids
The heam group is broken down to iron and bilirubin
The bilirubin is taken to the liver and conjugated, then excreted in bile
What benefits does glycolysis have for RBCs?
Prevents from oxidative damage and protects from free radicals
What is the rate limiting enzyme in glycolysis?
Glucose-6-phosphate
How do platelets form?
Pockets of cytoplasm ‘bud off’ from megakaryocytes
What is the morphology of megakaryocytes?
Large cells with large lobulated nucleus
What is the lifespan of platelets?
7-10 days
What are the white blood cells?
Neutrophils Eosinophils Basophils Monocytes Lymphocytes
What is the morphology of neutrophils?
Multi-segmented nucleus
Neutral staining granules
Express myeloperoxidase
What is the function of neutrophils?
Phagocytosis - kill by releasing granule contents
Recruitment of other immune cells
What can cause neutrophilia?
Acute inflammation - infection, trauma, infarction
Pregnancy
Drugs - steroids
What can cause neutropenia?
Aplastic anaemia
Pancytopenia
Drugs - clozapine, carbimazole
What is the morphology of eosinophils?
Bi-lobed (horseshoe)
Orange/red granules
What is the function of eosinophils?
Hypersensitivity
Fight against parasitic infections
What can cause eosinophilia?
Churg-Strauss syndrome
Atopy
Parasitic infections
Hodgkin’s
What is the morphology of basophils?
Large deep purple granules that can be so abundant they obscure the nucleus
What is the function of basophils?
Uncertain
Circulating version of tissue mast cell
Mediates hypersensitivity reactions
Granules contain histamine
What are basophils increased in?
CML
Polycythaemia rubra vera
What is the morphology of monocytes?
Large single nucleus (kidney shaped)
Faintly staining granules
Often vacuolated (contain white circles)
Large cytoplasm
What is the function of monocytes?
Circulate for a few days then enter tissues and become macrophages
As macrophages - phagocytes, antigen presentation
Attract other cells
What are monocytes increased in?
Chronic bacterial infections SLE RA Lymphoma Leukaemia
What is the morphology of mature lymphocytes?
Small
Condensed nucleus
Rim of cytoplasm
What is the morphology of activated (atypical) lymphocytes?
Large
Plentiful blue cytoplasm
Extend round neighbouring red cells
‘Open’ nucleus with chromatin pattern
What is the function of lymphocytes?
Lots of types and functions
Coordinate response to infection
What can cause lymphocytosis?
Infection
Malignancy
Hyposplenism
