7- The causes of anaemia Flashcards
What is haemopoiesis?
the production of all blood cells (wbc, rbc, platlets)
What are the main blood cells?
Red blood cells (erythrocytes)
white blood cells
platelets (thrombocytes)
What is special about haemopoietic stem cells?
- can self renew
- ability to differentiate
Briefly describe the haemopoietic lifecycle
stem cell -> multipotent progenitor cell -> commited (unipotent) progenitor cell -> precursor cell -> mature cell: RBC, WBC, platelets
What 2 things act upon the progenitor cells?
- hormones
2. cytokines
2 main lineages of hemocytoblast? (multipotential haemopoietic stem cell)
- common myeloid progenitor
- common lymphoid progenitor
what does the lymphoid progenitor produce?
- natural killer cell
- small lymphocyte (t/b cell)
what does the myeloid progenitor produce?
- megakaryocyte -> thrombocyte
- erythrocyte (rbc)
- mast cell
- myeloblast (basophil, neutrophil, eosinophil, monocyte)
What stimulates a megakaryocyte?
thrombopoietin to produce thrombocytes (platelets)
What stimulates erythrocyte production?
erythropoietin
Where does haemopoiesis take place?
bone marrow in red marrow
5 main white blood cells?
- lymphocytes
- basophils
- neutrophils
- eosinophils
- monocyte
myeloid progenitor how many wbc?
4/5
lymphoid progenitor how many wbc?
1/5
what is erythropoiesis
production of erythrocytes
erythrocyte cycle?
hemocytoblast -> proerythroblast -> early erythroblast ->late erythroblast -> normoblast (nucleus is ejected) -> reticulocte -> erythrocyte
What does a reticulocyte or normoblast present in blood suggest?
anaemia or red blood cell production problems
What does the term “blast” mean?
they are precursor cells and should only be found in bone marrow
When are reticulocytes released into circulation?
if RBC count is low
What is the shape of erythrocytes?
biconcave disc
What is the diameter of an erythrocyte?
7-8 micrometres
How do erythrocytes fit into capillaries?
they are flexible so fold into an arrowhead to fit
What are the cellular contents of erythrocytes?
Main component haemoglobin to carry oxygen
no organelles
What is the function of erythrocytes?
- carries O2 to be delivered to cells
- carries CO2 to be removed
What is the lifespan of an erythrocyte?
120 days
Why is the lifespan of an erythrocyte only 120 days?
membrane quite fragile, constantly squeezing into small blood vessels eventually breaks down in the spleen
Where do erythrocytes break down?
in the spleen and liver
What breaks down erythrocytes?
Macrophages
What is globin recycled into?
amino acids used for general protein synthesis
What is haem recycled into?
- into iron to be used in erythropoiesis
- converted into bilirubin becomes bile excreted
What are the WHO classifications of anaemia?
men haemoglobin less than 13g/dL
women haemoglobin less than 12 g/dL
What is the definition of anaemia?
Low levels of haemoglobin in the blood
What are the main causes of anaemia?
- Blood loss
- Impaired erythrocyte production
- Excessive erythrocyte destruction
What does anaemia cause morphological changes in?
- size
- shape
- colour of red blood cells
What does hypochromic mean?
RBC paler due to lack of haemoglobin
What does normochromic/normocytic mean?
Normal colour, normal size
What does microcytic mean?
Smaller than normal rbc (smaller mcv)
What does macrocytic mean?
Larger than normal rbc (greater mcv)
What are some signs and symptoms of anaemia?
- pale
- fatigue
- dyspnea (shortness of breath)
- palpitations
- headache
- tinnitus
- anorexia and bowel disturbance
What is the bodies physiological response of anaemia?
- 2,3 DPG levels rise
- Cardiac output increases
What does mcv mean?
Mean Cell Volume
What is 2,3 DPG levels?
A substance produced by RBC to help oxygen bind/upload to the tissue. It decreases the affinity to oxygen so that it is more easily given up
How much iron is present in 500ml of blood?
200-250mg
2 types of blood loss?
- Acute: loss of large volume of blood e.g. trauma
2. Chronic: bleeding unnoticed over a period of time
What deficiencies can cause impaired erythrocyte production?
- iron
- vitamin B12
- folate
What is the daily iron cycle?
the circulation of iron in the body,
How does iron circulate in the plasma?
Bound to transferrin
What does transferrin do?
Delivers iron to tissues that have transferrin receptors
How much iron do transferrin receptors have at any given time?
4mg
How much iron do we absorb per day in the gut?
1mg
How much iron should we have in our diet?
10-20mg
Where is iron absorbed?
Upper GI tract
What is iron needed for?
Synthesis of haemoglobin
What type of anaemia is iron deficiency
Microcytic
What are potential causes of iron deficiency?
- increased physiological demands - (growth spurt/pregnancy)
- chronic blood loss
3, inadequate intake - coeliac disease/ chrons disease ( malabsorption)
How does coeliac cause iron deficiency?
Impacts gastric mucosa, affects iron transporters, therefore, iron not being taken up even if meeting daily requirement
Clinical signs and symptoms of iron deficiency
- Koilonychia (spooning of nails)
- Angular stomatitis (lesions at corner of the mouth)
- Glossitis
- Pallor of skin + increased fatigue
Laboratory findings of iron deficiency?
- haemoglobin concentration decreased
- mcv reduced (microcytic cells)
- Hematocrit reduced
What type of anaemia is Vitamin B12 deficiency?
Macrocytic
Where is B12 found?
red meats but not vegetables
what does b12 require in order to be absorbed?
intrinsic factor (found in parietal cells of stomach)
Where is B12 absorbed in the GI tract?
Terminal ileum in GI tract
main cause of b12 deficiency?
- malabsorption (gastric diseases cause loss of intrinsic factor)
- Increased demands
Causes of B12 deficiency anaemia?
- inadequate diet (Vegans)
- increased demands
- deficiency of intrinsic factor
- intestinal causes affecting absorption (infection/loss of absorptive surfaces)
- drugs preventing absorption
Laboratory findings of b12 deficiency anaemia
- increaed mcv (macrocytic)
- thymidine deficiency
What is thymidine?
needed for DNA synthesis and nuclear maturation
What type of anaemia is folate deficiency?
Macrocytic
Where is folate (folic acid) found?
leafy veg
where is folate absorbed in GI tract?
upper GI tract
what are the causes of folate deficiency?
- malabsorption
- increased demands
- inadequate diet
- alcoholism (affects gi mucosa)
- antifolate drugs
What other things cause impaired erythrocyte production?
- chronic inflammation (affects bone marrow)
- chronic renal disease (affects kidneys)
- aplastic anaemia
- infiltration of marrow by leukaemia/lymphoma/carcinoma
- drug induced
- irradiation
what is aplastic anaemia
autoimmune disease causing deficiency of all blood types
3 main reasons of excessive erythrocyte production
- intracorpuscular defects
- extracorpuscular defects
- haemolytic anaemia
Name some intracorpuscular defects?
- abnormal haemoglobin
- erythrocyte membrane defects
- enzyme defects
What are intracorpuscular defects usually?
inherited (within RBC)
What type of haemoglobin does sickle cell produce?
haemoglobin S
what is the issue with producing haemoglobin s?
forms polymers in red blood cell so it doesn’t give up oxygen easily, causes rbc to change to sickle shape
What happens in thalassemia?
absence/reduction in one of the haemoglobin chains
how many chains do we have in haemoglobin normally?
- 2 alpha
- 2 beta
2 types of erythrocyte membrane defects?
- hereditary spherocytosis- cell becomes spherical, gets stuck easily so broken down prematurely
- Elliptocytosis - becomes pencil shaped
example of an enzyme defect causing excessive erythrocyte destruction?
G6PD needed in glycolysis impacts the way a RBC survives
Name some extracorpuscular defects that cause excessive erythrocyte destruction?
- immune (haemolytic disease of the newborn)
- incompatible blood transfusion
- drug induced (can break down rbc prematurely)
- infection (pneumonia, malaria)
- idiopathic (spontaneous unknown cause)
- mechanical (prosthetic valves)
- burns
What are extracorpuscular defects usually?
Acquired (outside rbc)
what is haemolytic disease of the newborn?
incompatibility with rhesus blood group
What are clinical features of patients with anemia?
- pallor
- tiredness/lethargy
- shortness of breath
- glossitis
- angular stomatitis
- oral ulcers
What is leukaemia?
Increased white cell count, reduced red blood cell and platelets
Main steps for investigation for anaemia?
- full blood count
- blood film picture
- bone marrow failure
- ferritin and iron-binding capacity
Why is anaemia important to dentist?
- anaemia may be obvious on examination
- may be a feature of infection (bleeding, easy to bruise)
- important to investigate, it is a symptom of a disease, important to find out actual cause
