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2.2 Haematology > The Erythrocyte > Flashcards

The Erythrocyte Flashcards

(90 cards)

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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
What cell type is involved in phase 1 of erythrocyte development
Early erythroblast
26
What happens in phase 1 of erythrocyte development
Ribosome synthesis
27
What cell types are involved in phase 1 of erythrocyte development
Late erythroblast Normoblast
28
What happens in phase 2 of erythrocyte development
Haemoglobin accumulation
29
What cell type is involved in phase 3 of erythrocyte development
Reticulocyte
30
What cell types of involved in the progression from normoblast to reticulocyte
Pronormoblast Basophilic normoblast Polychromatophilic normoblast Orthochromatic normoblast Reticulocyte
31
What was the role of bone marrow macrophages originally thought to be
That they scavenged and phagocytosed extruded nuclei
32
What is the role of bone marrow macrophages
Providing cytokines and other signals needed to promote erythropoiesis
33
How do macrophages promote proliferation of pro/erythroblasts into more mature cells (2)
The close physical proximity of the macrophage brought about by the interaction of adhesion molecules on both cell types Its characteristic cytoplasmic protrusions
34
What happens to erythroblasts which have been stimulated to mature (2)
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
35
What is the erythroblastic island in the bone marrow (3)
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
36
What happens after erythroblasts have interacted with macrophages?
Erythroblasts extrude their nuclei Nuclei are phagocytosed by macrophages Reticulocytes are released into circulation
37
What are reticulocytes
rbcs with remnants of ribosomal RNA
38
How do we identify reticulocytes
RNA reacts with methylene blue dye (basic dye) to produce a blue precipitate Can be counted using a flow cytometer and CD71
39
What is a normal reticulocyte count
Between 0.2 and 2%
40
Why would one have high reticulocytes (4)
Bleeding High altitude Haemolytic anaemia They are a baby
41
Why would one have low reticulocytes
Aplastic anaemia Iron deficiency anaemia Radiation
42
What growth factors control erythropoiesis
SCF EPO
43
What is EPO
An essential erythroid specific factor A hormone produced in the pertubular interstitial cells of the kidney (90%) and the liver (10%)
44
What is the molecular mass of EPO
34kDa
45
What happens when EPO is activated (3)
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
Where is JAK 2 receptor found
On developing rbcs in body
47
What pathway is mutated in a lot of leukaemias
JAK pathway
48
What activates EPO
Tissue hypoxia
49
EPO promotes cell division and differentiation into normoblasts in what cells (5)
CFU-GEMM BFU-E CFU-E Pro-Normoblast Basophilic normoblast
50
What are the effects of EPO
Shorten the cell cycle time of dividing cells Shorten the maturation time Inhibit apoptosis Promotes reticulocyte release from the bone marrow
51
What causes macrocytes (3)
Liver disease Alcoholism -> can be oval shaped in megaloblastic anaemia
52
What causes target cells (4)
Iron deficiency Liver disease Haemoglobinopathies Post-splenectomy
53
What are stomatocytes
rbcs with a rectangular pale patch in centre
54
What causes stomatocytes?
Liver disease Alcoholism
55
What causes pencil cells
Iron deficiency
56
What are echinocytes
Spiky rbcs
57
What causes echinocytes (3)
Liver disease Post-splenectomy Storage artefact
58
What are acanthocytes?
Misshapen rbcs
59
What causes acanthocytes
Liver disease Abetalipoproteinaemia Renal failure
60
What causes microspherocytes? (3)
Hereditary spherocytosis Autoimmune haemolytic anaemia Speticaemia
61
What causes rbc fragments (6)
DIC Microangiopathy HUS TTP Burns Cardiac valves
62
What are elliptocytes
Oval shaped rbcs
63
What causes elliptocytes
Hereditary elliptocytosis
64
What causes tear drop poikilocytes (2)
Myelofibrosis Extramedullary haemopoiesis
65
What causes basket cells (2)
Oxidant damage e.g. G6P deficiency Unstable haemoglobin
66
What causes sickle cells
Sickle cell anaemia
67
What causes microcytes (2)
Iron deficiency Haemoglobinopathy
68
List some RBC inclusions (6)
Howell-Jolly body Pappenheimer bodies (Siderotic granules) Basophilic stippling Malaria parasite Reticulocyte RNA Heinz bodies
69
What type of staining is needed for RNA and Heinz bodies
New Methylene Blue
70
What are Heinz bodies
Oxidised denatured Hb
71
What are siderotic granules
Granules containing iron Appear purple with conventional staining and blue with Perls stain
72
What is Howell-Jolly body
DNA remnant
73
What is basophilic strippling
Denatured RNA
74
What do we use red cell indices for
Classification of anaemia
75
What are the three red cell indices
MCV MCH MCHC
76
What is MCV
Average volume of the red cell, expressed in femtolitres (fL or 10^-15L)
77
What does MCV suggest
Cells are normocytic, macrocytic or microcytic
78
What is the equation for MCV
(Hct% x10)/ RBC (x10^12/L)
79
What is MCH
The average weight of Hb in the red cell, expressed as picograms (pg or 10^12g)
80
What is MCH
The average weight of Hb in the red cell, expressed as picograms (pg or 10^12g)
81
What is MCH
The average weight of Hb in the red cell, expressed as picograms (pg or 10^12g)
82
What does MCH suggest
RBCs are normochromic or hypochromic
83
What is the equation for MCH
(Hb g/L)/ RBC (x10^12/L)
84
What is MCHC
Average concentration of Hb in the RBC volume expressed as grams of haemoglobin Reported as g/L or g/dL
85
What is the equation for MCHC
(Hb g/L x 100)/Hct %
86
The loss of what molecules determine the time of death for rbcs (3)
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
What are the two types of rbc haemolysis?
Extravascular haemolysis (90%) Intravascular haemolysis (10%)
88
Where does extravascular haemolysis occur
Spleen Liver
89
Where does intravascular haemolysis occur
Within the circulation
90
How is haem broken down (2)
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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