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2.2 Haematology > The Erythrocyte > Flashcards

The Erythrocyte Flashcards

1
Q

How much blood does a 70kg man have

A

5.6L

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2
Q

What percentage of blood is water

A

78%

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3
Q

What temperature is blood

A

38 degrees

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4
Q

What is the pH of blood

A

7.35-7.45

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5
Q

What does blood carry to tissues
(7)

A

Oxygen
Water
Electrolytes
Hormones
Vitamins
Antibodies
Heat

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6
Q

What does blood carry away from the tissues

A

Waste matter (urea)

Carbon dioxide

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7
Q

What percentage of blood is plasma

A

55%

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8
Q

What percentage of blood is erythrocytes

A

45%

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9
Q

What are the formed elements of blood

A

Red cells (99%)
Platelets (1%)
WBC (1%)

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10
Q

Describe the structure of a rbcs
(4)

A

Biconcave disc to enhance the diffusion of gases by increasing surface area

Thin to enable oxygen to diffuse rapidly and alse increase flexibility

When mature they don’t have nuclei, mitochondria or other organelles

Packed full of haemoglobin

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11
Q

What is the diameter of an rbcs

A

7-8 micrometers

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12
Q

For how long do rbcs survive

A

120 days

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13
Q

What conditions are needed for an rbc to survive 120 days

A

Intact red cell membrane

Normal haemoglobin structure

Normal metabolic pathways

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14
Q

What happens if rbcs are damaged or not functioning correctly
(3)

A

They are removed by macrophages

The haemoglobin components are recycled
- iron is recycled
- globin is broken down into amino acids and haem is excreted in bile

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15
Q

What enzyme is found in rbcs which is involved in gaseous exchange

A

Carbonic anhydrase

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16
Q

What does carbonic anhydrase do

A

It takes CO2 and H2O and catalyses the creation of a stable molecule called bicarbonate

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17
Q

What does bicarbonate do

A

This is an easier form of carrying CO2

This acts as a buffer for the blood

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18
Q

What is the chemical formula for bicarbonate

A

HCO3-

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19
Q

Why is HCO3- considered more efficient of a molecule

A

It dissolves much better than CO2

Great quantities of CO2 can be transported this way without needing to be inside the small rbc

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20
Q

What happens when HCO3- dissolved in the blood arrives in the capillaries of the lung

A

HCO3- is converted back to gaseous CO2

CO2 then diffuses out into the lungs where it is breathed out

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21
Q

How long does it take reticulocytes to become rbcs

A

approx 2 days

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22
Q

What does increased reticulocytes mean

A

Disease or mass bleed

The bone marrow is under pressure to replace rbcs

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23
Q

What happens during the development from a proerythroblast to an erythrocyte
(4)

A

Cell keeps getting smaller

Cytoplasmic to nuclear ratio gets bigger

Haemoglobin accumulates

Nucleus shrinks and is eventually dispelled

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24
Q

List the cells involved in the maturation of the erythrocyte
(7)

A

Hemocytoblast

Proerythroblast

Early erythroblast

Late erythroblast

Normoblast

Reticulocyte

Erythrocyte

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25
Q

What cell type is involved in phase 1 of erythrocyte development

A

Early erythroblast

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26
Q

What happens in phase 1 of erythrocyte development

A

Ribosome synthesis

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27
Q

What cell types are involved in phase 1 of erythrocyte development

A

Late erythroblast

Normoblast

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28
Q

What happens in phase 2 of erythrocyte development

A

Haemoglobin accumulation

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29
Q

What cell type is involved in phase 3 of erythrocyte development

A

Reticulocyte

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30
Q

What cell types of involved in the progression from normoblast to reticulocyte

A

Pronormoblast

Basophilic normoblast

Polychromatophilic normoblast

Orthochromatic normoblast

Reticulocyte

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31
Q

What was the role of bone marrow macrophages originally thought to be

A

That they scavenged and phagocytosed extruded nuclei

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32
Q

What is the role of bone marrow macrophages

A

Providing cytokines and other signals needed to promote erythropoiesis

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33
Q

How do macrophages promote proliferation of pro/erythroblasts into more mature cells
(2)

A

The close physical proximity of the macrophage brought about by the interaction of adhesion molecules on both cell types

Its characteristic cytoplasmic protrusions

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34
Q

What happens to erythroblasts which have been stimulated to mature
(2)

A

They move to the sinusoids of the bone marrow which are close to blood vessels

This facilitates the migration of reticulocytes and erythrocytes into circulation

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35
Q

What is the erythroblastic island in the bone marrow
(3)

A

Erythroblastic islands are specialized microenvironmental compartments within which erythroblasts proliferate and differentiate.

These islands consist of a central macrophage that extends cytoplasmic protrusions to a ring of surrounding erythroblasts

Central macrophage provides further cues to induce erythroblast differentiation, expansion and haemoglobinisation

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36
Q

What happens after erythroblasts have interacted with macrophages?

A

Erythroblasts extrude their nuclei

Nuclei are phagocytosed by macrophages

Reticulocytes are released into circulation

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37
Q

What are reticulocytes

A

rbcs with remnants of ribosomal RNA

38
Q

How do we identify reticulocytes

A

RNA reacts with methylene blue dye (basic dye) to produce a blue precipitate

Can be counted using a flow cytometer and CD71

39
Q

What is a normal reticulocyte count

A

Between 0.2 and 2%

40
Q

Why would one have high reticulocytes
(4)

A

Bleeding

High altitude

Haemolytic anaemia

They are a baby

41
Q

Why would one have low reticulocytes

A

Aplastic anaemia

Iron deficiency anaemia

Radiation

42
Q

What growth factors control erythropoiesis

A

SCF
EPO

43
Q

What is EPO

A

An essential erythroid specific factor

A hormone produced in the pertubular interstitial cells of the kidney (90%) and the liver (10%)

44
Q

What is the molecular mass of EPO

A

34kDa

45
Q

What happens when EPO is activated
(3)

A

EPO signalled when blood volume is low

EPO receptor engagement results in JAK2 pathway activation

This acts on the BFU-E (burst forming unit)

46
Q

Where is JAK 2 receptor found

A

On developing rbcs in body

47
Q

What pathway is mutated in a lot of leukaemias

A

JAK pathway

48
Q

What activates EPO

A

Tissue hypoxia

49
Q

EPO promotes cell division and differentiation into normoblasts in what cells
(5)

A

CFU-GEMM

BFU-E

CFU-E

Pro-Normoblast

Basophilic normoblast

50
Q

What are the effects of EPO

A

Shorten the cell cycle time of dividing cells

Shorten the maturation time

Inhibit apoptosis

Promotes reticulocyte release from the bone marrow

51
Q

What causes macrocytes
(3)

A

Liver disease

Alcoholism

-> can be oval shaped in megaloblastic anaemia

52
Q

What causes target cells
(4)

A

Iron deficiency

Liver disease

Haemoglobinopathies

Post-splenectomy

53
Q

What are stomatocytes

A

rbcs with a rectangular pale patch in centre

54
Q

What causes stomatocytes?

A

Liver disease

Alcoholism

55
Q

What causes pencil cells

A

Iron deficiency

56
Q

What are echinocytes

A

Spiky rbcs

57
Q

What causes echinocytes
(3)

A

Liver disease

Post-splenectomy

Storage artefact

58
Q

What are acanthocytes?

A

Misshapen rbcs

59
Q

What causes acanthocytes

A

Liver disease
Abetalipoproteinaemia
Renal failure

60
Q

What causes microspherocytes?
(3)

A

Hereditary spherocytosis

Autoimmune haemolytic anaemia

Speticaemia

61
Q

What causes rbc fragments (6)

A

DIC
Microangiopathy
HUS
TTP
Burns
Cardiac valves

62
Q

What are elliptocytes

A

Oval shaped rbcs

63
Q

What causes elliptocytes

A

Hereditary elliptocytosis

64
Q

What causes tear drop poikilocytes
(2)

A

Myelofibrosis
Extramedullary haemopoiesis

65
Q

What causes basket cells (2)

A

Oxidant damage e.g. G6P deficiency
Unstable haemoglobin

66
Q

What causes sickle cells

A

Sickle cell anaemia

67
Q

What causes microcytes
(2)

A

Iron deficiency
Haemoglobinopathy

68
Q

List some RBC inclusions
(6)

A

Howell-Jolly body
Pappenheimer bodies (Siderotic granules)
Basophilic stippling
Malaria parasite
Reticulocyte RNA
Heinz bodies

69
Q

What type of staining is needed for RNA and Heinz bodies

A

New Methylene Blue

70
Q

What are Heinz bodies

A

Oxidised denatured Hb

71
Q

What are siderotic granules

A

Granules containing iron

Appear purple with conventional staining and blue with Perls stain

72
Q

What is Howell-Jolly body

A

DNA remnant

73
Q

What is basophilic strippling

A

Denatured RNA

74
Q

What do we use red cell indices for

A

Classification of anaemia

75
Q

What are the three red cell indices

A

MCV

MCH

MCHC

76
Q

What is MCV

A

Average volume of the red cell, expressed in femtolitres (fL or 10^-15L)

77
Q

What does MCV suggest

A

Cells are normocytic, macrocytic or microcytic

78
Q

What is the equation for MCV

A

(Hct% x10)/ RBC (x10^12/L)

79
Q

What is MCH

A

The average weight of Hb in the red cell, expressed as picograms (pg or 10^12g)

80
Q

What is MCH

A

The average weight of Hb in the red cell, expressed as picograms (pg or 10^12g)

81
Q

What is MCH

A

The average weight of Hb in the red cell, expressed as picograms (pg or 10^12g)

82
Q

What does MCH suggest

A

RBCs are normochromic or hypochromic

83
Q

What is the equation for MCH

A

(Hb g/L)/ RBC (x10^12/L)

84
Q

What is MCHC

A

Average concentration of Hb in the RBC volume expressed as grams of haemoglobin

Reported as g/L or g/dL

85
Q

What is the equation for MCHC

A

(Hb g/L x 100)/Hct %

86
Q

The loss of what molecules determine the time of death for rbcs
(3)

A

When rbcs run out of G6PD or pyruvate kinase

They can’t replenish these so the cell begins to lose its shape and flexibility

This damage is recognised by phagocytic cells

87
Q

What are the two types of rbc haemolysis?

A

Extravascular haemolysis (90%)

Intravascular haemolysis (10%)

88
Q

Where does extravascular haemolysis occur

A

Spleen

Liver

89
Q

Where does intravascular haemolysis occur

A

Within the circulation

90
Q

How is haem broken down
(2)

A

The protoporphyrin ring is broken down to iron, carbon monoxide and biliverdin

Biliverdin is further broken down into bilirubin by haemoxygenase

2.2 Haematology (38 decks)

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