Erythropoiesis Flashcards by pattie o.

Erythropoiesis

Process of RBC formation inside the bone marrow

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Erythron

Total mass of RBCs in peripheral blood and bone marrow RBC precursors

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RBC mass

Erythrocytes in the circulation

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Erythrokinetics

Dynamics of RBC creation and destruction (average lifespan 120 days)

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Ineffective erythropoiesis

Production of defective RBC precursors, often undergoing apoptosis in bone marrow

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Examples of ineffective erythropoiesis conditions

Vitamin B12 deficiency, folate deficiency, thalassemia, sideroblastic anemia

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Insufficient erythropoiesis

Decrease in RBC precursors, leading to decreased RBC production

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Examples of insufficient erythropoiesis conditions

Iron deficiency, renal disease, acute leukemia

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RBC survival test method

Label RBCs with chromium-51 (51Cr), track radioactivity decay to calculate survival time

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Normal RBC survival time range

28 to 38 days

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Anemia is classifies as

A sign, not a disease

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Immature hematopoietic cells committed to a cell line; cannot be identified

Progenitor cells

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Immature hematopoietic cells identifiable as belonging to a specific cell line

Precursor cells

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Earliest marker of erythroid differentiation

CD71 (transferrin receptor)

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Transport protein of iron in blood

Transferrin

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Primary cell source of erythropoietin (EPO)

Peritubular interstitial cells in kidneys

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Primary target cells of EPO

BFU-E and CFU-E

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Effects of EPO

1) Early release of reticulocytes from bone marrow, 2) Reduces maturation time in bone marrow, 3) Prevents apoptosis (major way EPO increases RBC mass)

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Therapeutic applications of EPO

Anemia of chronic renal disease, autologous blood donation, anemia in HIV infection

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“Blood doping”

Athletes use EPO injections to increase oxygen-carrying capacity, which can lead to thrombosis

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Growth hormone and erythropoiesis

Stimulates erythropoiesis, produced by pituitary gland

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Testosterone and erythropoiesis

Stimulates erythropoiesis, produced by testes

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Prolactin and erythropoiesis

Stimulates erythropoiesis, produced by pituitary gland

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Estrogen and erythropoiesis

Inhibits erythropoiesis, produced by ovaries

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Stages of RBC maturation

BFU-E → CFU-E → Rubriblast → Pro(basophilic) → rubriblast (polychromatophilic) → Meta(Orthochromatic) → Reticulocyte → Mature erythrocyte

Rubriblastic stages

Rubriblast → Prorubricyte → Rubricyte → Metarubricyte → Reticulocyte (seen in supravital stain) → Mature erythrocyte

Normoblastic stages

Pronormoblast → Basophilic (Early) Normoblast → Polychromatophilic/Intermediate Normoblast → Orthochromatic Normoblast (Late Normoblast) → Reticulocyte → Mature erythrocyte

Erythroblastic stages

Proerythroblast → Basophilic (Early) Erythroblast → Polychromatophilic Erythroblast (Intermediate Erythroblast) → Orthochromatic Erythroblast → Reticulocyte → Mature erythrocyte

Earliest committed erythroid progenitor

BFU-E (Burst forming unit- erythroid)

Second committed erythroid progenitor

CFU-E (Colony forming unit erythroid)

Time from BFU-E to CFU-E

1 week

Time from CFU-E to Rubriblast

1 week

Time for BFU-E to mature to erythrocyte

18 to 21 days

Time spent as recognizable precursors in bone marrow

Approximately 6 days

Supravital stains for reticulocytes

BCB (Brilliant cresyl blue), NMB (New methylene blue)

Reticulocytes under Wright stain

Polychromatophilic erythrocytes, Diffusely basophilic erythrocytes

Changes in erythroid precursors during maturation

Decrease in diameter, nuclear diameter decreases, chromatin becomes coarser, nucleoli disappear, cytoplasm changes from blue to salmon pink

N:C ratio definition

Nucleus to cytoplasm ratio, used to identify and stage RBC and WBC precursors

What does N:C ratio represent?

Visual estimate of nucleus and cytoplasm area in a cell

N:C ratio of 1:1

Nucleus and cytoplasm occupy approximately equal areas

N:C ratio <1:1

Nucleus occupies less than 50% of the cell area

N:C ratio >1:1

Nucleus occupies more than 50% of the cell area

What causes basophilia in cells?

Acidic components attracting basic stains (e.g., methylene blue)

What does the degree of basophilia correlate with?

Quantity of ribosomal RNA in the cell

What causes eosinophilia (acidophilia) in cells?

Accumulation of basic components attracting eosin (acid stain)

What does the degree of eosinophilia correlate with in RBCs?

Accumulation of hemoglobin as RBCs mature

What is the size of a Rubriblast (Pronormoblast)?

12 to 19 μm

What is the N:C ratio for Rubriblast (Pronormoblast)?

4:1 (Turgeon), 8:1 (Rodak)

What are key characteristics of Rubriblast (Pronormoblast)?

!! earliest recognizable erythroid precursor under a light microscope; Round or slightly oval nucleus, 1-2 nucleoli, dark blue cytoplasm due to ribosomes, smallest cytoplasm,

What does Rubriblast (Pronormoblast) give rise to?

Two prorubricytes

What is the size of a Prorubricyte (Basophilic Normoblast)?

12 to 17 μm

What is the N:C ratio for Prorubricyte (Basophilic Normoblast)?

4:1 (Turgeon), 6:1 (Rodak)

What are key characteristics of Prorubricyte (Basophilic Normoblast)?

carse chromatin, absence of nucleoli, last stage with nucleolus

What does Prorubricyte (Basophilic Normoblast) give rise to?

Four rubricytes

What is the first stage of hemoglobin synthesis in erythropoiesis?

Prorubricyte (Basophilic Normoblast)

What is the size of a Rubricyte (Polychromatic Normoblast)?

11 to 15 μm

What is the N:C ratio for Rubricyte (Polychromatic Normoblast)?

'1:1

What are key characteristics of Rubricyte (Polychromatic Normoblast)?

Round, smaller nucleus with a thick membrane, eccentric, no nucleolus, gray cytoplasm

What does Rubricyte (Polychromatic Normoblast) give rise to?

Two metarubricytes

What is the last stage for mitosis in erythropoiesis?

Rubricyte (Polychromatic Normoblast)

What is the first stage where cytoplasm becomes pink in erythropoiesis?

Rubricyte (Polychromatic Normoblast)

What is the difference in the nucleus between a Rubricyte and a Lymphocyte?

Rubricyte nucleus: checkerboard, Lymphocyte nucleus: crushed velvet

What is the difference in cytoplasm color between a Rubricyte and a Lymphocyte?

Rubricyte cytoplasm: muddy/gray, Lymphocyte cytoplasm: sky blue or robin egg blue

What is the size of a Metarubricyte (Orthochromatic Normoblast)?

8 to 12 μm

What is the N:C ratio for Metarubricyte (Orthochromatic Normoblast)?

'1:2

What are key characteristics of Metarubricyte (Orthochromatic Normoblast)?

Pyknotic nucleus, no nucleolus, salmon-pink cytoplasm

What happens to the nucleus at the Metarubricyte stage?

Nucleus is extruded and the cell becomes a reticulocyte

What are other names for Metarubricyte (Orthochromatic Normoblast)?

Nucleated RBC (NRBC), Pyknotic erythroblast, Acidophilic normoblast

What is the last stage with a nucleus in erythropoiesis?

Metarubricyte (Orthochromatic Normoblast)

What is a Pyrenocyte?

Enveloped extruded nucleus, engulfed by bone marrow macrophages

What are Howell-Jolly bodies?

Small fragments of nucleus left behind after projection pinching, seen in RBCs in circulation

What happens to Howell-Jolly bodies in circulation?

They are typically removed by splenic macrophages through pitting process

What is the size of a Reticulocyte?

7 to 10 μm

What is the predominant color of Reticulocyte cytoplasm?

Hemoglobin color with a bluish tinge due to residual ribosomes and RNA

What happens to the Reticulocyte by the end of its stage?

It becomes salmon pink

What is the last stage of hemoglobin synthesis?

Reticulocyte

What are Reticulocytes?

Young RBCs with residual RNA, the last immature erythrocyte stage

How long does a Reticulocyte spend in the bone marrow and peripheral blood?

2 to 3 days in bone marrow and 1 day in peripheral blood

What is the shape of a Reticulocyte in electron micrographs?

Irregular shape

What is the size of a Mature Erythrocyte?

6 to 8 μm

What is the color of a Mature Erythrocyte's cytoplasm?

Salmon pink with a central pallor occupying 1/3 of the cell’s diameter

What is the shape of a Mature Erythrocyte?

Biconcave disk

What is the thickness of a Mature Erythrocyte?

1.5 to 2.5 μm

What is the average life span of a Mature Erythrocyte?

120 days

How many erythrocytes are produced from each rubriblast?

8-32

What is the normal RBC to WBC ratio?

Approximately 600:1

What is the normal RBC to Platelet ratio?

Approximately 15:1

Does an Adult RBC contain mitochondria?

No, it contains no mitochondria

Erythropoiesis Flashcards

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