Blood Disorders Flashcards
what is the composition of blood?
55% plasma - water and proteins
45% other
- 99% erythrocytes
- leukocytes
- platelets
define haematocrit aka packed cell volume
the percentage of red blood cells
what is the function of blood? (4)
Transport
- gases - oyxgen and co2
- hormones
- enzymes
Combat Infection
- w/ antibody and leukocytes
Homeostasis
- regulate temperature, pH and volume
Haemostasis
- stops bleeding from a blood vessel
define anaemia
when the haemoglobin and red blood cells count falls below a certain range
why may there be apparent changes in haemoglobin concentration during dehydration or pregnancy, but not actually?
dehydrated
- the plasma vol decrease
- hb conc apparently increases
pregnancy
- the plasma vol increase
- hb conc apparently decreases
two ways in which anaemia is classified.
by red blood cell size
by their underlying aetiology
how do you work out the RBC size?
MCV
- mean corpuscular volume
what are the 3 classifications of anaemia?
small cells MCV = <80 = Microcytic Anaemia
MCV = 80-96 = Normocytic Anaemia/Haemolytic Anaemia
large cells MCV = >96 = Macrocytic Anaemia
what are the underlying mechanisms of anaemia?
- increased blood loss
- increased destruction = haemolytic anaemias
- impaired production of red cells
give an example of microcytic anaemia, MCV <80
iron deficient anaemia
what is iron deficiency anaemia?
when the level of iron in the blood is too low, causing a reduction in red blood cells
describe 4 causes of iron deficiency anaemia
- blood loss
- an increased demand
- decreased absorption of iron
- poor dietary intake
= microcytic and hypochromic
- RBC are smaller and paler
how can iron deficiency anaemia be investigated for diagnosis?
- do a blood count, microcytic (<80) and hypochromic (<27)
- do a blood film
- poikilocytosis - varies in shape
- anisocytosis - varies in size
- blood test for levels of iron
what is the MCH?
mean corpuscular haemoglobin
- average count of Hb in RBC
how does iron deficiency affect the MCV?
becomes microcytic
below 80
how can iron deficiency anaemia be treated?
iron tablets
iron-rich foods
what is the most common cause of microcytic anaemia?
iron deficiency anaemia
what are other causes of microcytic anaemia, apart from iron deficient?
- anaemia chronic disease
- thallasaemia
- sideroblastic anaemia
what is an example of macrocytic anaemia? MCV>96
Pernicious Anaemia
what is B12 deficiency/pernicous anaemia?
an autoimmune condition causing destruction of cells that produce intrinsic factor, leading to a decrease in B12 absorption and B12 deficiency
what are the causes of B12 deficiency? (6)
most common = autoimmune
- dietary
- surgery
- parasites
- drugs
- ileal disease - disease limited to the lower third of small bowel
describe the pathogenesis of B12 deficiency/pernicous anaemia.
- B12 from food passes into GIT
- binds to protein = Haptocorrin
- B12-HC complex move to stomach
- in stomach, B12-HC splits
- gastric parietal cells in stomach secrete intrinsic factor
- IF binds with B12
- both absorb in the small bowel
- if anything interferes with process = B12 deficiency
how is B12 deficiency/pernicous anaemia investigated?
- blood count
- MCV >96
- look at blood film
- oval macrocytes
- hypersegmented polymorphs
- if severe = leukopenia and thrombocytopenia
- look at bone marrow
- more megaloblasts = immature red-cells
what is the treatment for B12 deficiency/pernicous anaemia?
B12 injections
with B12 deficiency, there may be an increase of megaloblasts. what is this called?
megaloblastic anaemia
with pernicous anaemia, why do you actually get an increase in megaloblastic cells?
- with decreased B12
= DNA synthesis is impaired - impaired division and replication
- get more megaloblasts not maturing
What is Haemolytic Anaemia?
when RBC have short lifespan and break down quicker than usual
what is Normocytic Anaemia and most common cause?
MCV = 80-96, so RBC are normocytic and normochromic
most common cause = haemolytic anaemia
describe both ways in which you can develop normocytic anaemia. hereditary or acquired.
hereditary
- abnormal Hb synthesis = sickle cell
- RBC membrane defect
- metabolic pathway defect
= all of above lead to haemolytic anaemia
acquired
- immune mediated
- non-immune mediated
what is sickle cell anaemia?
a inherited single gene mutation, distorting the red blood cells
describe the cause of sickle cell anaemia.
- single gene mutation on the 6th codon of beta-globing chain
- valine gets substited for glutamic acid
= HbS - when O2 drops
- HbS molecules polymerise
= sickle-shaped cells
describe the results of sickle-cell anaemia
polymerisation
obstructs the small vessels - tissue infarction
how is sickle cell anaemia investigated?
- usually asymptomatic
- only symptomatic with VOC
= vaso-occlusive crisis - infection, dehydration, cold, acidosis, hypoxia
- very painful for the patient
- 30% acute chest syndrome
- vaso-occlusion can cause necrosis of tissues
- blood count = normal
- blood film = sickled cells
how is sickle cell anaemia treated?
- hospital
- iv fluids
- analgesia
what can be the oral manifestations resulting from anaemia?
- angular chelitis
- atrophic glossitis
- recurrent aphthous stomatitis - recurrent ulcers, commonly B12 def.
- dry, cracked mouth
- fat tongue
- mucous ulcers
what is haemostasis
the process of which blood clots form at sites of vascular injury
describe the process of haemostasis (4)
- vasoconstriction
- primary haemostasis - platelet plug formation
- secondary haemostasis - fibrin meshwork
- clot stabilisation
describe what happens during vasoconstriction.
blood flow is reduced
- endothelin is secreted
- tightens the blood vessel
= a temporary fix
describe primary haemostasis (5)
- endothelial disruption
- exposed collagen from the blood binds to von willebrand factor in the endothelial cells
- platelets adhere and activate
- platelets change shape = spiky
- aggregation
= platelet plug
describe secondary haemostasis.
- tissue factors are exposed from the endothelial
- coagulation cascade activates
- thrombin cleaves fibrinogen into fibrin
= meshwork - activate more platelets and traps RBC
3 ways in which why you may have defects in blood clotting.
- vessel wall is abnormal
- platelet deficiency/dysfunction
- abnormal coagulation
Describe VW Disease and Haemophilia A - bleeding disorders due to abnormalities in haemostasis?
Von Willebrand Disease
- autosomal inherited disorder
- Type 1
- 80% of people have
- decreased VWF
- Type 2
- 20% of people have
- dysfunction
Type 3
- rare/severe
- no VWF at all
Haemophilia A
- X linked recessive (males)
- Factor 8 mutation = impaired coagulation
- easy bruising/haemorrhage
How is Von Willebrand Disease treated?
with desmopressin or plasma infusions
how is Haemophilia A treated?
infusion of F8
define pathophysiology
physiological processes which are disordered due to association with disease or injury
what is the pathophysiology of disseminated intravascular coagulation?
manifestations of abnormalities in bleeding and clotting
- lots of tissue factor is released
= lot of thrombosis
need to break it down
= break down thrombus
= widespread bleeding
= vascular occlusions
= ischaemic tissue damage
