Unit 2 Flashcards
Describe mature erythrocyte
- a bioconcave disc with a central pallor that occupies the middle one third of the cell.
- has hemoglobin
- average lifespan of 120 days
- soft and pliable cell
What is the function of hemoglobin?
- oxygen-carbon dioxide transport
Describe as the RBCs age
- decrease in enzyme activity, especially glycolysis
Describe erythropoiesis
- the process of erythrocyte production
- encompasses differentiation form the HSC through the mature erythrocyte
Describe where erythropoiesis takes place?
- erythroblastic islands
- they consists of normoblasts (erytrhoblasts) clustered around an iron-laden macrophage. The macrophage provides the iron needed for hemoglobin maturation and also aids by providing cytokines for the developing normoblasts to mature into functional erythrocytes
What does heme pigment accomplish?
- transport of oxygen to the tissues and transport of carbon dioxide from the tissues
- heme pigment is synthesized as RBC matures
What are the basic substances needed for normal erythrocyte and hemoglobin production?
- amino acids (protein)
- iron
- vitamin B12
- vitamin B6
- folic acid
- trace mineral cobalt and nickel
- abnormal erythropoiesis can result from deficiencies. Of any of these necessary substances
What is erythropoietin produced by?
- 80-90% are produced by peritubular cells of the kidneys
- 10-20% is produced in the liver, which is primary site of EPO production in the developing fetus
What are blood levels of EPO inversely related to?
- to tissue oxygenation
- the greater the hypoxia, the higher the EPO levels
What is the main function of EPO?
- early-acting and lat-acting cytokine, acting on BFU-E and CFU- progenitors as well as the erythroblastic precursors
- it also interacts with IL-3, GM-CSF, IL-1 and TSF to promote maturation and differentiation of other cell types
Describe maturation and development of a erythrocyte
- once the stem cell differentiates into the erythroid cell line, a call matures through the nucleated cell stages in 4 or 5 days
- Bone marrow reticulocyte psi have an average maturation period of 2.5 days
-once young reticulocyte enters the circulating blood, they remain in the reticulocyte stage for an average of 1 day - reticulocyte represent approximately 0.5% to 1.5% of the circulating erythrocytes
What is the order for erythrocyte development?
- Rubriblast
- Prorubricyte
- Rubricyte
- Metarubricyte
- Reticulocyte
- Mature erythrocyte
OR
1. Pronormoblast
2. Basophilic normoblast
3. Polychromatic normoblast
4. Orthochromic normoblast
5. polychromatic erytrhocyte
Decribe rubriblast
- 12-19 um in diameter
- N:C ratio is 4:1
- nucleus —> larger, round nucleus, fine pattern chromatin
- 0-2 nucleoli
- cytoplasm - distinctive basophilic color without granules
Describe prorubricyte
- 12-17 um in diameter
- Nucleus - chromatin is more clumped
- nucleoli usually not apparent
- cytoplasm has distinctive basophilic color
Describe rubricyte
- 11-15 um is diameter
- N:C ratio 1:1
- nucleus - increased clumping of chromatin
- cytoplasm - color: variable, with pink staining mixed with basophilia
Desribre metarubricyte
- 8-12 um in diameter
- nucleus - chromatin pattern is tightly condensed
- cytoplasm color: reddish pink (acidophilic)
Describe the stain used for reticulocyte
- methylene blue precipitates the ribosomal RNA in these cells to form a deep-blue, mesh-like network
What is the reticulocyte procedure used for?
As an indicator of the rate of erythrocyte production
Describe the reticulocyte count procedure
- usually, the count is expressed as a % of total erythrocytes.
- the normal range is:
—> 0.5-1.5% in adults
—> 2.5-6.5% in newborns, falls after the second week of life
What is the equation for corrected reticulocyte count?
CRC (%) = (Retic count (%) X patients PCV)/normal PCV
*normal PCV is based on age and sex
Describe Reticulocyte production index (RPI)
- a simple percentage calculation of reticulocyte does not account for an existing anemia, which prematurely releases reticulocytes. These require an additional 0.5-1.5 days longer to mature
- measures erythropoietic activity when stress reticulocytes are present. The rational for this is that life span of the circulating stress reticulocytes is 2 days instead of the normal 1 day
What is the RPI equation?
RPI = corrected reticulocyte count %/ maturation time in days
What are the maturation time correction factors?
Hct 45% —> 1.0 days
Hct 35% —> 1.5 days
Hct 25% —> 2.0 days
Hct 15% —> 2.5 days
Describe the mature erythrocytes
- is anucleated
- functions to transport oxygen to the tissues via hemoglobin
- survives in circulation for 120 days
- has average diameter of 6-8 um
- lacks ability to make hemoglobin, lacks nucleus and functional organelles