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Clinical Pathology > Erythrocytes > Flashcards

Erythrocytes Flashcards

1
Q

What is an Erythron?

A
  • All erythroid cells
    • includes mature erythrocytes circulating in blood
    • Immature erythroid cells in the bone marrow
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2
Q

What is an Erythrogram?

A
  • A numerical or graphical representation of RBCs as seen in the CBC data
  • Morphologic assessment of the RBCs
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3
Q

What is Erythropoiesis?

A
  • The process of RBC production in health there is a balance between production and loss of RBCs
  • Erythropoiesis is tightly regulated by what the body needs
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4
Q

What is Anemia?

A
  • A deficiency of RBCs and/or hemoglobin
    • In Vet med primarily determined by HCT or PCV
  • RBC production < RBC loss
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5
Q

What is Erythrocytosis?

A
  • An increase in RBC mass
  • RBC production > RBC loss
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6
Q

What is sHct on the Erythrogram?

A
  • spun Hct or PCV
  • Percentage of blood volume occupied by erythrocytes
    • reflects RBC mass in periferal blood
  • Obtained via centrifugation of microhematocrittubes
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7
Q

What is Hgb on the Erythrogram?

A
  • Blood hemoglobin concentration
    • Hgb is intact & lysed with RBCs
  • Obtained by spectrophotometry:
    • lyse RBCs in blood
    • Add reagent to bind Hgb and produce color
    • Amount of color = HgB
  • Should be ~⅓ the Hct in animals w/ disc-shaped RBCs
  • Plasma turbidity (lipemia) can give a false increase in Hgb
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8
Q

What is RBC on the Erythrogram?

A
  • RBC = Erythrocyte concentration in peripheral blood
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9
Q

What is MCV, MCH, and MCHC on the Erythrogram?

A
  • MCV: mean cell volume (avg RBC volume)
  • MCHC: mean cell Hgb conc (avg [Hgb] in RBC)
  • MCH: mean cell Hgb (avg Hgb content in RBC)
  • Changes in the MCV and MCHC for patterns that are associated with different disease processes
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10
Q

What does the MCV indicate?

A
  • Tells us average volume (size) but not the distribution of sizes
  • High = Macrocytic
  • Normal = Normocytic
  • Low = Microcytic
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11
Q

What is Red cell distribution width (RDW)?

A
  • RDW is a quantitative index of RBC size and heterogeneity
  • Indicates the degree of variation in RBC size
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12
Q

What is Anisocytosis?

A
  • variability in RBC size
  • detected by evaluation of a blood smear or by looking a a graph
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13
Q

What does the MCHC indicate?

A
  • MCHC = ({Hgb] x100) / Hct
  • Low = hypochromic
  • Normal = normochromic
  • High = hyperchromic
  • used to classify the type of anemia
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14
Q

How can you tell if a CBC is accurate?

A
  • cHct is calculated
  • sHct = spun
  • Should be within 3% of each other if handled correctly
  • if the difference is >3% there is a mismatch that needs to be explained
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15
Q

What is the morphology of RBCs?

A
  • Most species have a round, bi-concave shape - thinner in the middle than at the edges
    • This shows as Central pallor
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16
Q

What are Polychromatophils?

A
  • Occurs in young RBCs
    • Released early
  • Usually larger and more blue/purple (from RNA)
  • Presence/absence of polyhromatophils is important in determining if anemia is regenerative or nonregenerative
  • Horses are unique:
    • typically do not release polychromatophilic cells
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17
Q

How to determine a polychromatiophilic erythrocyte vs a reticulocyte?

A
  • Cell has polychromasia
  • Blood has increased polychromasia
  • “polychromatophil”
  • Blood has a reticulocytosis
  • “reticulocyte”
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18
Q

What is Rubricytosis?

A
  • Nucleated red blood cells (nRBCs)
  • Early or inappropriate release from hemic tissue
  • Significance:
    • Regenerative anemias – appropriate rubricytosis
      • blood loss or hemolysis
    • Nonregenerative anemias w/ or w/out anemia - inappropriate rubricytosis
      • Marrow damage - inflammation, necrosis, etc
      • Lead poisoning in dogs
      • Extramedullary hematopoiesis, splenic contraction, splenectomy
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19
Q

What is the significance Anisocytosis?

A
  • Anisocytosis - variation in sizes
  • Depends on reason for variation of size
  • Macrocytes
    • incomplete maturation or skipped cell division
  • Microcytes
    • Decreased volume (also hypochromic)
  • Spherocytes
    • Normal volume
    • Decreased amount of membrane
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20
Q

What is the significance of macrocytosis?

A
  • Macrocyte: Increased diameter, Increased volume
  • Usually means increased erythropoiesis
    • release larger immature cells
  • Increased MCV with anisocytosis due to macrocytosis is the best evidence of increased erythropoiesis & bone marrow response to anemia in equine CBC
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21
Q

How are microcytes made?

A
  • Increased cell divisions during development
  • decreased volume (⇣MCV)
  • Causes:
    • Iron deficiency
    • Hepatic insufficiency (portosystemic shunts)
    • Breed variations
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22
Q

What do spherocytes look like?

A
  • Lack central pallor
  • apparent hyperchromasia
23
Q

What is Poikilocytosis?

A
  • Variation in shape
  • Significance - depends on the type of poikilocyte
  • 2 types:
    • Echinocyte
    • Acanthocytes
24
Q

What is an Echinocyte?

A
  • Often regularly spaced projections
  • Artifact - cell dehydration
  • Envenomation (rattle snake)
  • Other diseases by not consistently
25
Q

What is an Acanthocytes?

A
  • Irregularly spaced projections
  • Altered lipid metabolism
  • Liver disease (cats)
  • Hemangiosarcoma (dogs)
26
Q

What causes the projections on echinocyte/acanthocytes?

A

Increased cholesterol or phospholipid in outer lipid bilayer

27
Q

What is a schistocytes

A
  • Fibrin strand that breaks apart erythrocytes
  • Occurs in Microangiopathic diseases
    • DIC
    • hemangiosarcoma
    • glomerulonephritis
    • myelofibrosis
28
Q

What are Keratocytes?

A

irregularly shaped RBCs with a enlarged blister-like vesicle

29
Q

What are Codocytes?

A
  • Target cells
  • Central focus of Hgb surrounded by ring of pallor
  • Formation: excess membrane relative to amount of Hgb
30
Q

What are Heinz bodies?

A
  • Indicate oxidative damage
  • Large, membrane bound, aggregates of denatured hemoglobin (sulfhemoglobin)
31
Q

What are eccentrocytes?

A
  • Fused, unstained, crescent-shaped region of membrane, with a shift of hemoglobin to the opposite side
  • Hallmark of severe oxidative damage
    • Combination of:
      • Direct oxidative injury to membrane
      • Force to bring membrane sides together
32
Q

What are Pyknocytes?

A
  • Not spherocytes
    • different pathophysiology
  • Loss of fused membrane portion of eccentrocytes
33
Q

What is basophilic stippling?

A
  • Formation: ribosomal RNA not degraded
  • Significance: regenerative anemia, lead poisoning
34
Q

What is a Howell-jolly body?

A
  • Nuclear remnant
  • Most importantly do not call these parasites
  • Significance:
    • Low numbers in health
    • Regenerative anemia
35
Q

What are some of the RBC organisms?

A
  • Anaplasma marginale
  • Babesia sp.
  • Cytauxzoon felis
  • Mycoplasma sp. (Haemobartonella sp.)
36
Q

What do distemper inclusions look like?

A
  • Pink RBC inclusions with Diff quick
  • Blue with Modified Wright’s Stain
37
Q

How are Rouleaux and Agglutination different?

A
  • Rouleaux is a charge attraction
    • nonspecific sign of inflammation
    • Normal in a horse
    • Will separate with added saline
  • Agglutination is antibody-related cell bridging
    • Used to diagnose Immune mediated hemolytic anemia
    • IgG or IgM
    • Does NOT separate with added saline
38
Q

What is the physiology of RBCs?

A
  • Function: The primary function of RBCs is to carry O2 from the lungs to the tissue
    • Also transport CO2 from the tissue to the lungs and buffer H+
  • Properties:
    • Flexibility: In part due to the flexible membrane and shedding of the nucleus
    • Strength: Strong but flexible membrane able to withstand recurrent shear forces involved in blood circulation
    • Shape: Biconcavity allows for increased surface area for gas exchange
    • Hemoglobin content: Unique to the red cell, hemoglobin is pivotal to the development and oxygen transport ability due to its affinity for oxygen
    • Lifespan: Because the mature RBC has no nucleus, the cell cannot divide or repair itself. The lifespan is, therefore relatively short and varies between species
39
Q

What is RBC deformability?

A
  • Ability to change shape in response to stress AND recover once the stress is removed
  • Allows RBCs to move through the circulation without loss of structural integrity and is a major determinant of blood viscosity
  • Dependent on:
    • structure of the membrane and cytoskeleton
    • High surface area to volume ratio
    • Low viscosity cytoplasm
      • .33% solution of hemoglobin
  • Alterations in the lipid or protein composition of the membrane may result in abnormal red-cell shapes
40
Q

What are the Red Cell Life spans?

A
  • Mouse - 40 days
  • Rat - 65 days
  • Cat 75 days
  • Dog 120 days
  • Human 130
  • Cow 140
  • Horse 150
41
Q

What is Erythropoiesis?

A
  • Production of erythrocytes form stem cell to circulating RBC
  • Complex process that occurs in the bone marrow
    • Most effective, other tissues (spleen) too
  • Before a RBC arrives in the blood stream it must develop from a stem cell and progress through a number of stages.
42
Q

What is the main regulator of erythropoiesis?

A
  • Tissue oxygenation
    • Renal peritubular interstitial cells produce erythropoietin (Epo) in response to renal hypoxia
      • Anemia
      • Poor oxygenation of blood
      • Poor renal perfusion
43
Q

What happens when [Erythropoietin] is high?

A
  • Erythroid hyperplasia
    • Shortened erythroid maturation time
    • Increased hemoglobin synthesis in dividing cells
    • Decreased apoptosis of progenitor cells in the bone marrow (CFU-E, rubriblasts, prorubricytes)
44
Q

What happens when [Erythropoietin] is persistently low

A
  • Erythroid hypoplasia
    • RBC production < RBC loss
    • Gradual onset of anemia
  • Causes:
    • Decreased functional renal tissue
    • Inflammation
45
Q

What is the other regulator of erythropoiesis?

A
  • Iron
    • A deficiency in iron can result in anemia through impaired red cell production within the bone marrow (causes hypochromasia)
  • Iron is at the center of a heme molecule in Ferrous (Fe2 = reduced) state
    • reversibly binds oxygen
46
Q

What is the other regulator of erythropoiesis?

A
  • Iron
    • A deficiency in iron can result in anemia through impaired red cell production within the bone marrow (causes hypochromasia)
  • Iron is at the center of a heme molecule in Ferrous (Fe2 = reduced) state
    • reversibly binds oxygen
47
Q

What is the rate-limiting step for erythropoiesis?

A

Hemoglobin concentration

48
Q

Why is carbon monoxide so dangerous?

A

200x greater affinity for Hgb than O2

49
Q

What are the 2 iron pools?

A
  • 25-40% of body iron is in storage
  • Stored as:
    • Ferritin
    • Hemosiderin
50
Q

How is Ferritin stored?

A
  • A small amount of ferritin can be detected in the circulation
    • indirectly reflects how much iron is in the storage pool
  • Serum ferritin
    • ⇣ in iron deficiency
    • ⇡ for many reasons
51
Q

What is Hemosiderin?

A
  • Stable form of stored iron
  • Aggregate of denatured ferritin
  • Less readily available for use than ferritin
  • Dark grey to black with routine stains
    • Prussian blue stain can detect this form of storage iron
  • Not seen in the bone marrow of healthy cats
52
Q

What is Heme synthesis?

A
  • Occurs in RBC precursors
  • Can only occur in cells that have mitochondria
  • ALA synthase is major rate-limiting enzyme
    • Requires Vit B
53
Q

How does lead poisoning affect heme synthesis?

A
  • Inhibits 4 enzymes in the pathway
    • ALA-Synthase
    • ALA Dehydratase
    • Coproporphyrinogen oxidase
    • Ferrochelatase
54
Q

What happens to Bilirubin in health?

A
  1. Product of hemoglobin breakdown
  2. Senescent red cells are phagocytized by macrophages
    • Hemoglobin ⇢ Heme and globin
      • Globin ⇢ AA
      • Heme ⇢ Fe and protoporphyrin ⇢ bilverdin ⇢bilirubin
  3. Bilirubin released from macrophages, binds to plasma proteins, transported to liver
  4. Taken up by hepatocytes via membrane carriers
  5. Attaches to a binding protein- ligandin (y and z proteins) - in hepatocyte cytoplasm - prevents efflux back into blood
  6. Conjugated with glucuronic acid (glucose in horses) - now is water soluble
  7. Secreted into biliary system, stored in gall bladder
  8. Excreted into small intestine as part of bile
    1. Bacterial reduction ⇢ urobilinogen which can be passively absorbed and recirculates to be excreted in bile or urine
      1. Recirculates in portal system or renal excretion
      2. Some degraded to stercobilnogen and excreted in feces

Clinical Pathology (12 decks)

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