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Y2 MCD - Haematology > Physiology of blood cells and haematological terminology > Flashcards

Physiology of blood cells and haematological terminology Flashcards

1
Q

What are all types of blood cells derived from?

A

Multipotent haematopoietic stem cells in the bone marrow

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2
Q

Describe the stem cell heirarchy.

A
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3
Q

What is an essential characteristic of stem cells and how is this achieved?

A

They have the ability to self-renew and produce mature progeny (i.e. differentiate)

They can divide into two cells with different characteristics:

  • One is another stem cell
  • One is capable of differentiating into mature progeny
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4
Q

Describe the normal erythroid maturation process.

A
  1. Multipotent lymphoid-myeloid stem cell
  2. Myeloid stem cell
  3. Proerythroblast
  4. Erythroblast (have early, intermediate and late stages)
  5. Erythrocyte (RBCs)
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5
Q

What is the process of producing RBCs called?

A

Erythropoeisis

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6
Q

What does eythropoeisis require?

A

Erythropoeitin (hormone)

Secreted into capillaries (bloodsteam) and results in increased bone marrow activity and RBC production

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7
Q

Where is erythropoeitin synthesised?

A

Kidney juxtatubular interstitial cells (90%)

Liver (10%)

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8
Q

What triggers the production of erythropoeitin?

A

Hypoxia

Anaemia

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9
Q

What is the lifespan of erythrocytes?

A

120 days - ultimately destroyed by phagocytic cells of spleen

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10
Q

What is the main function of erythrocytes?

A

Oxygen transport - also transports some carbon dioxide

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11
Q

Describe the development pathway of some of the WBCs that multipotent haematopoetic stem cells give rise to? What does this require?

A

Development pathway:

  1. Multipotent lymphoid-myeloid stem cell
  2. Myeloid stem cell
  3. Granulocyte-monocyte which gives rise to:
    • Myeloblast → granulocyte (neutrophil, eosinophil, basophil)
    • Monoblast → monocyte

This development process needs:

  • Cytokines e.g:
    • G-CSF (granulocyte colony-stimulating factor)
    • M-CSF (granulocyte-macrophage colony-stimulating factor)
    • GM-CSF (macrophage colony-stimulating factor)
  • Various interleukins
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12
Q

What is the lifespan of neutrophils?

A

Survives 7–10 hours in the circulation before migrating to tissues

NOTE: Lifespan of WBCs refers to how long they survive in circulation if not activated - if they are activated then they will migrate into tissues

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13
Q

What is the main function of neutrophils?

A

Defence against infection

  • It phagocytoses and then kills micro-organisms
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14
Q

What is the lifespan of eosinophils?

A

Less than neutrophils - i.e. spends less time in the circulation than neutrophils

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15
Q

What is the main function of eosinophils?

A

Defence against parasitic infections

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16
Q

What is the lifespan of basophils?

A

Hours - days

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17
Q

What is the main function of basophils?

A

They have a role in allergic responses

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18
Q

What is the lifespan of monocytes?

A

Several days

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19
Q

What is the main function of monocytes?

A

They migrate to tissues where they develop into macrophages and other specialized cells that have a phagocytic and scavenging function

Macrophages also store and release iron

20
Q

What is the lifespan of lymphocytes?

A

Variable

  • Lymphocytes recirculate to lymph nodes and other tissues and then back to the bloodstream
  • Therefore, their intravascular life span is very variable
21
Q

What is the main function of lymphocytes?

A

To respond to foreign invaders in the body

22
Q

What is the lifespan of platelets?

A

10 days

23
Q

What is the main function of platelets?

A

They have a role in primary haemostasis

  • Contribute phospholipid which promotes blood coagulation
    • Activated platelets express negatively charged phospholipids (e.g. phosphatidylserine) on their surfaces
    • This provides a site for the assembly of enzyme substrate complexes required for certain reactions in the coagulation cascade
24
Q

Define anisocytosis.

A

RBCs show more variation in size than is normal

25
Q

Define poikilocytosis.

A

RBCs show more variation in shape than is normal

26
Q

Define microcytosis.

A

RBCs are smaller than normal

NOTE: In order to determine if RBCs are smaller or larger than normal, you can use lymphocytes for reference on a blood film

  • Lymphocytes are generally all the same size so can be a fairly reliable comparison
  • Normocytic RBCs are similar to the size of a lymphocyte nucleus
27
Q

Define macrocytosis.

A

RBCs are larger than normal

28
Q

Define microcyte and macrocyte.

A

Microcyte = a RBC that is smaller than normal

Macrocyte = a RBC that is larger than normal

29
Q

State 3 types of macrocytes.

A
  • Round
  • Oval
  • Polychromatic
30
Q

Define macrocytic, normocytic and microcytic.

A

Microcytic = describes RBCs that are smaller than normal OR an anaemia with small RBCs

Normocytic = describes RBCs that are of normal size OR an anaemia with normal sized RBCs

Macrocytic = describes RBCs that are larger than normal OR an anaemia with large RBCs

31
Q

Explain the colour you would see in normal RBCs.

A

Normal RBCs have about a third of the diameter in the centre that is pale

  • This is a result of the disk shape of the RBC
    • The centre is flatter than the rim
  • The centre has less haemoglobin as it is flatter (less space for Hb) and is therefore paler
32
Q

Define and explain hypochromia.

A

Hyochromia = RBCs have a larger area of central pallor than normal

  • This results from a lower haemoglobin content and concentration and therefore a flatter cell
  • Red cells that show hypochromia are described as hypochromic
  • Hypochromia and microcytosis often go together
33
Q

Define and explain hyperchromia.

A

Hyperchromia = RBCs lack central pallor

  • This can occur because they are:
    • thicker than normal
    • their shape is abnormal (so even if there was pallor it wouldn’t be in the centre)
  • Cells showing hyperchromia can be described as hyperchromatic OR hyperchromic

Generally hyperchromia has many causes since many abormally shaped cells lack the central thinner (pale) area and can therefore be described as hyperchromic

34
Q

What are the two important types of cells which are hypochromic?

A

Spherocytes

Irregularly contracted cells

35
Q

Define spherocytes and explain how they form.

A

Spherocytes = RBCs that are approximately spherical in shape

  • They therefore have a round, regular outline and lack central pallor
  • They result from the loss of cell membrane without the loss of an equivalent amount of cytoplasm so the cell is forced to round up
36
Q

What would hereditary spherocytosis look like on a blood film?

A

Spherocytes would be present BUT not all the cells would be spherical

Go over notes - see if it says why

37
Q

Define and explain irregular contracted cells.

A

Irregularly contracted cells = irregular in outline but are smaller than normal cells and have lost their central pallor

  • They usually result from oxidant damage to the cell membrane and to the haemoglobin
  • COME BACK TO THIS
38
Q

Define and explain polychromasia.

A

Polychromasia = describes an increased blue tinge to the cytoplasm of a RBC

  • It indicates that the RBC is young (i.e. immature)
  • Immature RBCs are known as reticulocytes
    • Appears slightly bluer under the standard stain maybe because the cytoplasm contains other stuff as well as Hb (e.g. network of residual rRNA)
    • This could take up the stain differently, altering the colour that the cell appears as
39
Q

Desribe another way to detect reticulocytes.

A

By doing a reticulocyte stain

  • This exposes living red cells to new methylene blue, which precipitates as a network or ‘reticulum’
    • The reticular (mesh-like) network of residual rRNA present in the cytoplasm is particularly taken up by the stain
    • The RNA network shows up as dark blue making the reticulocytes clearer to visualise
  • NOTE: rRNA - remains as ribosomes are being lost during maturaion process
40
Q

Compare polychromasia and reticulocyte identification.

A

Detecting polychromasia or increased numbers of reticulocytes gives you similar information

  • Polychromatic cells represent reticulocytes so they are a good guide of reticulocyte count
  • BUT not all reticulocytes show up on the blood film as polychromatic

However, identification of reticulocytes is more reliable so they can be counted

41
Q

State some different shapes poikilocytes come in.

A
  • Spherocytes
  • Irregularly contracted cells
  • Sickle cells
  • Target cells
  • Elliptocytes
  • Fragments

NOTE: Poikilocytosis = RBCs show more variation in shape than is normal

42
Q

Define target cells and state in what conditions they occur.

A

Target cells = cells with an accumulation of haemoglobin in the centre of the area of central pallor

They occur in:

  • Obstructive jaundice
  • Liver disease
  • Haemoglobinopathies
  • Hyposplenism (reduced splenic functioning)
43
Q

Define elliptocytes and state in what conditions they occur.

A

Elliptocytes = RBCs which are elliptical in shape

They occur in:

  • Hereditary elliptocytosis (picture on the left)
  • Iron deficiency (picture on the right) - check notes
44
Q

Define sickle cells an explain how they form.

A

Sickle cells = RBCs which are sickle or crescent shaped

  • They result from the polymerisation of haemoglobin S when it is present in a high concentration
    • Due to an AA mutation contacts form between protein chains of different HbS molecules - i.e. polymerisation
    • This causes the protein chains to stretch and deform the RBCs
45
Q

Define fragments and state what they indicate.

A

Fragments (also known as schistocytes) = small pieces of RBCs

  • They indicate that a red cell has fragmented
46
Q

Define rouleaux and state what they result from.

A

Y2 MCD - Haematology (13 decks)

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