RED BLOOD CELL- IIERYTHROPOIESIS

Dr. Elizabeth JProf & HOD,AIMS &RC, Bangalore

04/09/14

STAGES / FACTORS REGULATING

Scheme

Definition Theories of erythropoiesis Sites of erythropoiesis Stages of erythropoiesis Description of blast cells Reticulocyte Mature Red Cell Factors affecting Erythropoiesis Erythropoietin Absorption of Vitamin B12

DEVELOPMENTMULTIPLICATIONMATURATIONDIFFERENTIATION

DEFINITION

STOCHASTIC THEORY

HAEMPOIETIC INDUCTIVE MICROENVIRONMENT

HUMORAL FACTORS

“Theories that address the process of commitment of stem cell progeny”

3 stages of erythropoiesis during intrauterine life

o mesoblastic (1st 3 months)o hepatic (after 3 months)o myeloid (3rd trimester)

Site of Erythropoiesis

PHSC Pluripotent Hemopoietic stem cell

BFU-E Burst Forming Unit Erythrocyte

CFU-E Colony Forming Unit Erythrocyte

PROERYTHROBLAST

BASOPHILIC ERYTHROBLAST

POLYCHROMATOPHILIC ERYTHROBLAST

ORTHOCHROMATIC ERYTHROBLAST

RETICULOCYTE

ERYTHROCYTEERYTHROCYTE

E

R

Y

T

H

R

O

P

O

I

E

S

I

S

GM CSF erythro IL-1,IL-6,IL-3

GM CSF erythro

ERYTHROPOIESIS

15-20µm- basophilic cytoplasm, nucleus with nucleoli.

14-17µm-mitosis, basophilic cytoplasm, nucleoli disappears.

10-15µm- ’POLYCHROMASIA’Hb appears, nucleus

condenses.

7-10µm- PYKNOTIC Nucleus.Extrusion, Hb is maximum.

7.3µm- Reticulum of basophilic material in the cytoplasm.

7.2µm- Mature red cell with Hb.

BFU-E CFU-E

STAGES OF ERYTHROPOIESIS

Proerythroblast• Earliest erythroid element

• Basophilic cytoplasm with a

perinuclear halo

• Cytoplasm bulges to form

“Ear shaped” process

• Nuclear chromatin is not

homogenous & Nucleolus is seen

Basophilic erythroblast/Early normoblast

• Smaller than Proerythroblast

• Nuclear chromatin shows

sharp contrast between light

& dark areas

• Cytoplasm is basophilic

reflecting protein & RNA contents

Polychromatophilic erythroblast/Intermediate normoblast

• Polychromasia means

having many colors

• Nucleus mature & condensed

• Cytoplasm has a gray hue

derived from Hb (Hemoglobin)

Orthochromatic erythroblast/Late normoblast

• Acidophilic erythroblast which is

the last precursor with a nucleus

• Nucleus is compact & situated

near the membrane

• Cytoplasm is like mature red cell,

reflecting a high Hb content

Reticulocyte

-Young erythrocytes with granular or reticular filamentous structures

-Makes up 0.5-2% of all erythrocytes

-Vital staining required to make this visible.

-Reticulocytosis seen following hemolysis or acute blood loss

Reticulocyte as seen under the SEM

Mature non-nucleated erythrocyte

• Reddish, circular, biconcave cells

• 7-8 µ

• No visible internal structure

• High Hb content

• Bright at centre due to biconcave

shape

Erythrocyte as seen under the SEM

Erythropoietin (EPO): major humoral

regulator of erythropoiesis Interleukins, IL3,IL6 & IL1 Iron VitaminB12(Cyanocobalamine)+Folic Acid +

Vitamin C(Ascorbic Acid) Intrinsic factor for absorption of B12

FACTORS AFFECTING ERYTHROPOIESIS

PHSC

PROERYTHROBLAST

ERYTHROCYTE

TISSUE OXYGENATION

ERYTHROPOIETINERYTHROPOIETIN

DECREASES

KIDNEY

ERYTHROPOIETIN PRODUCTION

ERYTHROPOEITIN

Glycoprotein MW-34000.

90% formed in endothelial cells of the peritubular capillaries of the renal tubules.

10% formed in liver, hepatic cells & Kupffer cells.

ERYTHROPOEITIN (contd)

Stimuli for production hypoxia, high altitude, anemia, chronic lung or heart diseases, catecholamines, prostaglandins & androgens.

Formed in hours, RBC’s take 2-3 days to appear in peripheral blood.

Intrinsic Factor + Vitamin B12

Vitamin B12 (in a bound state protected by gastric enzymes)

Binds to mucosal cells of ileum

Absorbed into blood by pinocytosis

ABSORPTION OF VITAMIN B 12