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Hematology (F&F) > RBC morphology and damage > Flashcards

RBC morphology and damage Flashcards

1
Q

RBC morphology

A

Typically a biconcave shape with a shallow center. This allows for maximum surface area to volume ratio which optimizes gas exchange and allows them to fold and move through vasculature easily

  • Mammals= anucleate
  • Amphibians, reptiles and birds= nucleate
  • Less biconcavity for cat, horse, cow, sheep, goat compared to canine meaning that the lighter dot in the middle will be smaller
  • Camelid family are oval shaped
  • Horse and cats have Rouleux formation
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2
Q

Rouleaux formation

A
  • Common in horse and cats
  • RBCs stick together and look like a stack of coins
  • Can also appear due to poor preparation of the smear or by viewing the slide in a thickened area but can also indicate clinical symptoms in other species
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3
Q

Erythrocyte morphological characteristics

A

Colour (polychromasia vs. hypochromasia)
- Hypo= not enough colour/hemoglobin
- Poly= too much colour, still have ribosomal RNA in cytoplasm

Size (microcytic vs. macrocytic)

Shape (poikilocytes)

Inclusions (Heinz bodies, basophilic stippling)

Pattern (eg. Rouleaux)

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4
Q

Where to observe RBCs on a slide?

A

Slightly off from the feathered edge

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5
Q

Erythrocyte membrane formation

A
  • Lipid composition of phospholipids and cholesterol
  • Membrane proteins and cytoskeleton (spectrin Bands 1 &2 and actin Band 5)
  • Alterations can alter shape and make it hard for them to travel through vasculature
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6
Q

Microcytic Erythrocytes

A
  • Cells are smaller than normal which will correspond with a low MCV
  • Most commonly caused by iron deficiency anemia
  • Erythoid precursors continuing to divide until a near normal complement of Hb concentration is reached, resulting in small erythrocytes
  • Cells do not have enough iron to make sufficient hemoglobin
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7
Q

Macrocytic erythrocytes

A
  • Cells are larger than normal, corresponds with high MCV
  • Most common cause is increased numbers of immature erythrocytes that are polychromatophilic on Wright-stained blood films (reticulocytes)
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8
Q

Types of abnormally shaped erythrocytes (poikilocytes)

A
  • Spherocytes
  • Eccentrocytes
  • Heinz bodies
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9
Q

Spherocytes

A
  • A poikilocyte
  • Lack central pallor
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10
Q

Eccentrocytes

A
  • A poikilocyte
  • Associated with oxidative damage
  • Due to lipid peroxidation
  • Hemoglobin is shifted to one side
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11
Q

Heinz bodies

A
  • A poikilocyte
  • Associated with oxidative damage Ex. Onion toxicity in dogs
  • Aggregates of denatured hemoglobin
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12
Q

Oxidative damage in erythrocytes

A

Occurs when there is an imbalance between the production of reactive oxygen species (ROS) and the cell’s ability to counteract their harmful effects using antioxidants

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13
Q

Sources of ROS in RBCs

A
  • Endogenous: oxygen transport
  • Exogenous: exposure to drugs, toxins, etc.
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14
Q

Why are RBCs vulnerable to oxidative damage?

A

RBCs lack a nucleus and cannot replace damaged proteins AND hemoglobin is prone to oxidation to form methemoglobin

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15
Q

Antioxidant defence mechanisms

A

Use Glutathione system and Hexose Monophosphate shunt (Pentose phosphate pathway) catalyzed by Glucose-6- phosphate dehydrogenase (G6PD)

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16
Q

Consequences of oxidative damage

A
  • Formation of Heinz bodies
  • Formation of eccentrocytes
17
Q

Clinical significance of oxidative damage to erythrocytes

A
  • Some drugs and chemicals induce oxidative damage (eg. Onions, garlic)
  • Breeds with a deficiency in G6PD are more susceptible to oxidative damage
18
Q

Components of glycolysis that assist RBCs

A
  1. Bohr effect of 2,3 BPG shifts O2-Hb dissociation curve to the right by binding to oxygen and making it better at delivering oxygen to tissues
  2. Methemoglobulin reduction pathway: NADH from glycolysis is used to reduce HbFe3+ to HbFe2+ which ensures that oxygen can bind to hemoglobin
  3. Hexose monophosphate shunt- Glucose 6-phosphate dehydrogenase makes NADPH from glucose 6-phosphatase. NADPH reduces glutathione which is important in removing ROS.
    - Selenium is essential cofactor for this pathway.
19
Q

White muscle disease

A

Lack of selenium and therefore inability to conduct hexose monophosphate shunt is known as white muscle disease.

20
Q

Anemia

A

Deficiency in O2 carrying capacity therefore lack of RBCs

21
Q

What is anemia due to?

A

Low RBC count or hemocrit
- Reduced production (lack of vitamins, iron, etc.)
- Increased destruction (hemolysis)
- Increased loss of blood volume

Low hemoglobin content
- Iron deficiency

22
Q

How are anemias classified?

A
  1. According to RBC parameters
    - Size (microcytic, macrocytic)- look at MCV
    - Hemoglobin content (hypochromic, normochromic)- look at Hgb content
  2. According to bone marrow response
    - Regenerative (increase in reticulocytes)
    - Non-regenerative (no increase of reticulocytes)
23
Q

What causes hemolytic anemia?

A

Destruction of RBCs (immune, drugs/toxins, hereditary)

24
Q

What causes hemorrhagic anemia?

A

blood loss

25
Q

What causes dyshemopoietic anemia?

A

Bone marrow dysfunction

26
Q

When can absolute reticulocyte count be used?

A

Can only be used in species that have a normal amount of immature RBCs in circulation and then can see whether there is an increase or not

Eg. Can use in dogs or cats, but can’t use in horses because they do not generally release reticulocytes

27
Q

Four types of anemia during RBC maturation

A
  1. Aplastic anemia- occurs at rubriblast stage due to bone marrow defect. Body does not make enough blood cells
  2. Megaloblastic Anemia- occurs due to poor DNA synthesis (lack of nutrients and inability to complete mitosis). At the prorubricyte stage.
  3. Iron deficiency anemia- occurs at rubricyte stage (hemoglobin production) when lack of iron.
  4. Hemolytic anemia- destruction of mature RBCs by the immune system
28
Q

RBC maturation and size

A

As RBCs mature, they decrease in size

29
Q

Macrocytosis

A

Large immature cells present within circulation

30
Q

Erythrocytosis

A
  • Too many RBCs
  • Two types: relative and absolute
31
Q

Relative erythrocytosis

A
  • Due to decreased plasma volume or erythrocyte redistribution

Eg. Dehydration and body fluid shifts

Ex. Splenic contraction (common in horses)

32
Q

Absolute erythrocytosis

A
  • Primary absolute polycythemia- occurs independent of erythropoietin concentration. RARE.
  • Secondary absolute erythrocytosis- overproduction of erythrocytes in response to increased erythropoietin concentration. Due to generalized hypoxia, localized hypoxia or renal.
33
Q

What will bloodwork display for erythrocytosis?

A
  • Increased PCV/hematocrit, RBC count, Hemoglobin concentration
  • Will have normal MCHC

Hematology (F&F) (11 decks)

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