Blood Disorders Flashcards by Simran Sandhu

what is the composition of blood?

55% plasma - water and proteins

45% other
- 99% erythrocytes
- leukocytes
- platelets

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define haematocrit aka packed cell volume

the percentage of red blood cells

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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

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define anaemia

when the haemoglobin and red blood cells count falls below a certain range

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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

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two ways in which anaemia is classified.

by red blood cell size
by their underlying aetiology

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how do you work out the RBC size?

MCV
- mean corpuscular volume

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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

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what are the underlying mechanisms of anaemia?

increased blood loss
increased destruction = haemolytic anaemias
impaired production of red cells

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give an example of microcytic anaemia, MCV <80

iron deficient anaemia

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what is iron deficiency anaemia?

when the level of iron in the blood is too low, causing a reduction in red blood cells

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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

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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

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what is the MCH?

mean corpuscular haemoglobin
- average count of Hb in RBC

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how does iron deficiency affect the MCV?

becomes microcytic
below 80

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how can iron deficiency anaemia be treated?

iron tablets
iron-rich foods

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what is the most common cause of microcytic anaemia?

iron deficiency anaemia

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what are other causes of microcytic anaemia, apart from iron deficient?

anaemia chronic disease
thallasaemia
sideroblastic anaemia

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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)

1. vasoconstriction 2. primary haemostasis - platelet plug formation 3. secondary haemostasis - fibrin meshwork 4. 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)

1. endothelial disruption 2. exposed collagen from the blood binds to von willebrand factor in the endothelial cells 3. platelets adhere and activate 4. platelets change shape = spiky 5. 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