Hem 2 - Red Blood Cells Part 1

Question 1

what is a buffy coat

Answer 1

its the fraction of an anticogulated blood sample after centrifugation that contains most of the leukocytes and platelets

Question 2

species variation in erythrocyte morphology

Answer 2

mammalian erythrocyte is anuclear whereas all the other vertebrates have nucleated RBCs

Question 3

formation of blood cells: hemoatopoiesis: what is it, where does it occur, origination, lineage, types of poeisis

Answer 3

-hemotopoiesis is the development of blood cells. Prenatally, it occurs in the yolk sac, then liver, and eventually in the bone marrow

-in normal adults it occurs in the bone marrow

-pool of progenitor cells originates from bone marrow stem cells

-further lineage commitment depends on the variet of growth factors or colony stimulating factors

-can occur elsewhere (spleen, liver as extramedullary hematopoeisis) when marrow production is insufficient

-erythropoesis = RBCs; leukopoeisis = WBCs; thrombopoeisis = platelets

Question 4

what is the first RBC/erythrocyte precuroser that we can visualize in smears

Answer 4

rubriblast

Question 5

what is the first stage of precursor in the maturation pool of erythropoeisis

Answer 5

rubricyte

Question 6

how long does it take for a RBC to mature

Answer 6

5-6 days

Question 7

regulation of erythropoesis (4)

Answer 7

cell-cell interactions, hematopoeitic inductive environment, macrophage and lymphocyte factors, erythropoietin

Question 8

erythropoietin (EPO) - other names, what is it produced by, how does it act, what happens with EPO deficiency

Answer 8

-also called hematopoietin or hemopoietin that regulates RBC production

-EPO is primarily produced by kidney (adult) and liver (fetus)

-EPO acts by binding to a specific erythropoietin receptor on the surface of red cell precursors in the bone marrow, stimulating them to transform into mature RBCs and causing proliferation of red cell precursors

-because the kidneys are often the primary source of erythropoietin, chronic kidney disease often results in a systemic deficiency of EPO and consequent anemia

Question 9

what do we need to ask if there is hypoxia

Answer 9

is it losing too many red cells or is it just not making enough

Question 10

where does erythropoietin occur in adults vs fetus

Answer 10

adults = kidneys
fetus = liver

Question 11

lifespan of erythrocytes in dogs

Answer 11

100 days

Question 12

destruction of RBC - replacement, changes, major site of RBC removal, major predisposing factor for demise of RBC

Answer 12

-average 60k of the 6 million RBCs/microliter in circulation are replaced dairy

-biochemical and cellular changes leading to death of RBC are still speculative (glycosylation of surface proteins?)

-spleen is the major site of normal and abnormal removal of RBCs

-reduction in deformability is a major predisposing factor for the demise of RBC

Question 13

what is heme catabolized by and what happens

biliverdin cycle

what happens to bilirubin in the liver

Answer 13

heme is catabolized by an enzyme heme-oxygenase to produce Iron and biliverdin

biliverdin is reduced to bilirubin and is released into the circulation

in the liver, bilirubin is dissociated from albumin and enters hepatocytes where its conjugated to uridine diphosphoglucuronide to form bilirubin-diglucuronide

the conjugated bilirubin is excreted in the intestine where its reduced to urobilinogen

Question 14

morphology of red cells in circulation and clinical/physiologic implications

Answer 14

types of red cells present and their appearance can provide substantial information about how effectively they are being made, whether they are being damaged or destroyed, and whether the animal has sufficient nutrients and resources to effectively produce new blood cells when conditions demand increased production (eg hypoxia)

Question 15

reticulocytes - what are they, size, used to assess what, where are they retained, what happens in severe conditions

Answer 15

-immature enucleated erythroid cells with considerable quantities of ribosomal or mitochondrial RNA

-they are slightly larger than RBCs

-reticulocyte count is an accurate method of assessing marrow erythroid activity - when present it suggests that the marrow has the ability and resources (iron) to produce red cells

-normally, most reticulocytes are retained in the marrow until they mature to erythrocytes with a small fraction released

-in severe conditions, metarubricytes (nucleated blood cells) may enter the blood along with reticulocytes

Question 16

what stain can be used to better visualize reticulocytes in blood

Answer 16

methylene blue

Question 17

polychromasia - what is it, how does it appear, what is it an indicator of

Answer 17

-variation in the staining pattern of erythrocytes

-erythrocytes show a faint bluish tint due to an admixture of the colours of hemoglobin and the basophilic erythrocyte cytoplasm

-many of these would be shown to be reticulocytes if stained with methylene blue

-polychromasia (presence of reticulocytes) is an indicator of a productive marrow response

Question 18

significance of increased reticulocyte numbers

Answer 18

when sufficient iron, nutrients and bone marrow function are present, animals release reticulocytes into the bloodsteam in direct proportion to the regenerative response. Varies with species (esp horses, poor response), Therefore, their presence indicates a productive marrow response

Question 19

red cell morphology and morphologic changes - what changes do they undergo ,what can it reflect

Answer 19

red cells often undergo change in shape, colour or content that are microscopically visible

changes can reflect the primary problem or physiologic responses to such problems

by looking at the nature of such changes, we can often get a sense of the nature of the primary problem, how severe it is and sometimes how likely it is to resolve

Question 20

morphologic descriptions of RBCs (or conditions involving changes in RBC) (11)

Answer 20

• normocytic = normal RBC size
  -anisocytosis = variation in RBC size
  -marcoyte = cells with increased volume and diameter
  -microcyte = cells with decreased volume and diameter
  -hypochromic = decreased hemoglobin content and staining intensity
  -normochromic = normal staining intensity
  -polychromasia = variation in staining intensity and colour
  -basophilic stippling = bluish inclusions scattered throughout the cytoplasm
  -heinz bodies = hemoglobin precipitates appearing as refractile inclusions
  -howell-jolly bodies = chromatin residues in RBC
  -acanthocyte poikilocyte, leptocyte, spherocyte, schistocyte = describe specific morphologic changes in the shape and size of erythrocytes. pathologic

Question 21

hypochromasia - what is it, how does it appear, when is it observed

Answer 21

-decrease of hemogloin in erythrocytes so that they are abormally pale
-hypochromasia is frequently oberved in iron deficiency anemia as caused by chronic blood loss or parasitism