Erythrocytes aka RBC

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Erythrocytes aka RBCs

• Laboratory Procedures

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Hematopoietic System

• Blood supplies cells with water, nutrients,
  electrolytes, and hormone.
• Removes waste products
• Mainly CO2
• Cellular elements supply oxygen (RBC), protect
  against foreign organisms (WBC) and initiate
  coagulation (platelets).
• Clotting factors

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Blood Composition

• Separates into three components
• Red Blood Cells (RBCs)
• White Blood Cells and platelets (buffy coat)
• Plasma
• Bottom 1/3 to ½ of tube contains the heaviest of
  cellular material (the RBCs).

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HematocritPCV (Packed Cell Volume)

• To determine hematocrit, whole blood is
  centrifuged to pellet the red blood cells.
• Plasma remains on the top of the red cells.
• The fraction of blood that is packed is the
  hematocrit and is read as a percentage.

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Hemoglobin (Hgb)

• Normal values are usually 1/3 of the hematocrit.
• Each hemoglobin molecule has 4 heme units
  attached to globulins.
• Abnormal heme groups, cannot carry oxygen.
• Carboxyhemaglobin- Hgb has a higher affinity for
  CO than O2.
• Bright red blood
• Methemoglobin- The Fe molecule is oxidized to
  Fe3.
• Blood becomes brown.
• Tylenol toxicity in cats.

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Red Blood Cells

• Function
• Carry oxygen to the tissues
• Oxygen must be carried at enough pressure to
  permit rapid diffusion of oxygen.
• The RBC is a vehicle for hemoglobin which is the
  carrier molecule for oxygen.
• The sigmoid shape of curve is a result of the
  cooperative binding from the 4 hemoglobin
  molecules.

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Transport of oxygen in the blood

• 97 of oxygen transported from lungs to the
  tissues is carried in chemical combination with
  hemoglobin in RBCs.

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Erythropoiesis

• Production or Maturation of a RBC.
• Only occurs in the bone marrow of normal adult
  animals.
• Occurs in the spleen and liver of the fetus.
• Maturation time usually takes 5 days.
• Regulated by erythropoietin (EPO) which is
  increased in the presence of hypoxia.
• In most species, the kidney is the sensor organ
  and major site of EPO.

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Red Blood Cells (Erythrocytes)

• No nucleus due to have to fold and squeeze
  through tight spaces.
• Normocytes- cells look normal

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Erythrocyte Life Span

• Dog- 110 days
• Cat- 70 days
• Cow- 160 days
• Horse- 145 days
• Man- 120 days
• Mouse- 30 days

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Erythrocyte Life Span

• Stem Cell ? Rubriblast ? Prorubricyte ? Rubricyte
  ?Metarubricyte? Reticulocyte ? RBC
• Metarubricyte- nucleated RBC releases in severe
  anemia.
• No more mitotic division takes place after this
  stage.
• One rubriblast may give rise to as many as 8-32
  RBCs.

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Normal Erythrocytes

• Morphologic features vary from species to species
• Dogs Biconcave disk shape with central pallor
• Cats Generally round with little central
  pallor.
• Birds Contain a nucleated RBC

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Categories of Erythrocyte Characteristics

• 1. Cell arrangement on the blood film.
• 2. Size
• 3. Color
• 4. Shape.
• 5. Presence of structures on erythrocytes

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Cell Arrangement on Blood Film

• Rouleaux
• Rouleaux formation is a group of erythrocytes in
  stacks. This can be a sign of increased
  fibrinogen or globulin concentration.
• It can also be an artifact seen in blood that is
  held too long before preparing the blood slide or
  in blood that has been refrigerated.

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Cell Arrangement Continued

• Agglutination
• Agglutination, which appears as rouleaux, occurs
  in immune-mediated disorders. An antibody coats
  the cell causing bridging or clumping.
• If you add a drop of saline to a drop of blood
  rouleaux formation will disperse and
  agglutination will not

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Size

• Terms
• Anisocytosis
• Variations in size
• Can indicate anemia
• Macrocytosis
• Larger than normal cell size
• Liver disease or Vitamin B12 deficiency
• Microcytosis
• Smaller than normal cell size
• Iron deficiency

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MCV

• Mean Corpuscular Volume
• Describes cells as normocytic, microcytic, or
  macrocytic. Calculates the average volume of
  rbcs.
• MCV(Hematocrit x 10)/RBC count in millions
• Normal 66-77
• (we will come back to this calculation again)

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Color

• Polychromasia
• Polychromatic erythrocytes exhibit a bluish tint.
  The tint is due to a small amount nucleus
  retained in the cytoplasm. These are young cells
  and may appear as a reticulocyte
• Hypochromasia
• is a decrease in color, due to a decreased
  staining intensity caused by insufficient
  hemoglobin within the cell.
• Iron deficiency is the most common cause.
• Hyperchromasia
• refers to cell that appears darker than normal
  cells. This gives the appearance that the cell
  is over saturated with hemoglobin. The
  erythrocyte has a fixed maximum capacity for
  hemoglobin and over saturation can NOT occur.

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MCHC

• Mean Corpuscular Hemoglobin Concentration
• describes cells as normochromatic or
  hypochromatic.
• MCHC (Hgb)/(Hct) x 100
• Normal is 31-36
• (we will come back to this calculation again)

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Polychromasia
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Hypochromasia
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Hypochromasia continued

• Hypochromatic should be differentiated from cells
  with the center punched out. A punched out
  appearance can be an artifact due to improper
  smear technique

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Hyperchromasia

• True hyperchromasia does not exist.

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Shape

• Poikilocytosis
• Poikilocytosis is a major deviation in the normal
  shape of the erythrocyte. The term
  poikilocytosis is an umbrella term that is used
  for any and all abnormally shaped erythrocytes
  and does not suggest a specific diagnosis

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Schistocytes (Fragmented Cells)

• Also known as poikilocytes.
• RBCs with abnormal shape.
• Formed as a result of shearing of the cell by
  fibrin strands. This occurs when red blood cells
  rapidly pass through microvasculature that is
  lined or meshed with strands.
• They are observed in fragmentation hemolysis
  caused by DIC, vascular neoplasia, endocarditis,
  and possibly iron deficiency anemia.

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Acanthocytes (Spur Cells)

• The term acanthocyte is derived from the Greek
  word acanthi meaning thorn Acanthocytes are
  cells with five to ten irregular, blunt,
  finger-like projections.
• The projections with vary in width, length and
  surface distribution. These cells are seen in
  animals with altered lipid metabolism such as
  cats with hepatic lipidosis or dogs with liver
  disease.

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Acanthocytes Continued
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Echinoctyes (Burr Cell)

• Echinocytes have multiple, small, delicate
  regular shaped spines evenly distributed around
  the cell and are indistinguishable from
  artificially crenated cells.

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Echinoctyes Continued

• Echinocyte formation can be artificial, often
  seen with slow drying blood films or if the EDTA
  tube was underfilled. This artifact is then
  termed crenation.
• Echinocytes have been associated with renal
  disease, lymphosarcoma and rattlesnake bites in
  dogs.
• They can been seen after exercise in horses.

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Crenation

• Identified as the presence of many irregular
  membrane projections involving most RBCs.
• It is usually an artifact due to slow drying of
  the blood film.
• Commonly observed in pig blood but can be seen in
  any species.

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Drepanocytes (Sickle cell)

• These cells are crescent shaped with pointed
  ends.
• Drepanocytes are often seen in normal blood of
  deer and goats. It is thought to be a result of
  low oxygen tension.

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Drepanocytes
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Keratocyte (Helmet Cells)

• Also called blister cells or bite cells.
  Keratocytes are associated with trauma especially
  cellular damage from contact with fibrin strands.
  

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Prekeratocytes

• Cells with pseudovacuoles are called blister
  cells or pre-keratocytes.

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Spherocytes

• Cells have a spheroid shape instead of the usual
  biconcave disk shape.
• Have reduced cell membrane and are hypochromatic.
• Seen most frequently in autoimmune hemolytic
  anemia (AIHA).
• Usually seen in dogs.

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Stomatocytes

• The appearance of stomatocytes with their oval or
  rectangular central pallor has been compared to
  a smiling face, a fish mouth, and a coin slot.
• Stomatocytes are associated with a hereditary
  condition but are also seen in liver disease,
  acute alcoholism (humans), and electrolyte
  imbalances.

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Target Cells and Folded Cells

• Two types of leptocytes observed mainly in dogs.
• Represent cells with an increases
  membrane-to-volume ratio not specific to any
  disease.
• The cell membrane is thin and flimsy.

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Target Cells (Bulls Eye Cells)

• Also called codocytes
• Thin, bell-shaped cells
• Centrally stained area
• May be seen as
• artifacts when smears
• made in high humidity
• or if blown dry.
• Can indicate liver disease or hemoglobinopathies.
  

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Target Cells
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Anulocytes

• These are bowl shaped erythrocytes that form as a
  loss of membrane flexibility that does not allow
  the cell to return to a normal shape after
  passing through a capillary. They can occur due
  to lowed hemoglobin concentration or as an
  artifact.

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Dacryocytes (tear drop cells)

• These tear drop shaped cells are seen in
  myeloproliferative diseases. These cells, when
  produced as an artifact can be identified by the
  direction of their tail.

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• Dacryocytes produced as an artifact have their
  tails pointing in the same direction.

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Nucleated Red Blood Cells (NRBCs)

• Nucleated red blood cells (NRBC) usually
  represent early release of immature red blood
  cells during anemia.
• These are nuclear remnants seen in young
  erythrocytes during a response to anemia.

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Basophilic Stippling

• Observed in RBCs that contain abnormal
  aggregation of RNA.
• Can be observed in cases of heavy metal poisoning
  with non-regenerative anemias or intense
  erythrogenesis in dogs, cats, and ruminants.

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Howell-Jolly Bodies

• Nuclear remnants observed in young erythrocytes.
• Often observed in cats and horses.
• Can be seen in regenerative anemic animals.
• Also may be seen with splenic disease or in an
  animal with the spleen removed.

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Heinz Bodies

• Particles of denature hemoglobin protien.
• They stain with new methylene blue and appear as
  colorless bumps with quick stain.
• May be caused by oxidant drugs and chemicals.
  Also associated with onion toxicity in dogs!
• Normal cat blood may have 2-3.
• Spleen recognizes as abnormal and starts to lyse
  the cells.

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Heinz Bodies
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Reticulocytes

• These are immature red blood cells that contain
  organelles (ribosomes) that are lost in the
  mature cell. Cats have two forms of
  reticulocytes.
• The aggregate form contains large clumps of
  reticulum. They mature into the punctate form
  within 24 hours.
• The punctate form, unique to cats, contains two
  to eight singular granules. Punctate
  reticulocytes circulate for 7-10 days before the
  all the ribosomes are lost.

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Reticulocytes in the Peripheral Blood

• Non-nucleated cell containing RNA which can be
  easily seen when stained with methylene blue.
• Hallmark of erythrocyte regenerative response.