Functions of RBC
Transport of oxygen from lungs to tissues
Transport of CO2 from tissues to lungs
Regulation of acid – base balance
Red Blood cell / Erythrocytes
Biconcave, non-nucleated cell
Mean cell diameter = 6.9 -7.5 µm 7.2
Max. thickness at the edges is
2µm
Min. thickness at the center is
1 µm
Normal Erythrocyte Count
Males – 5 – 5.5 million cells / mm3
Females – 4.5 -5 million cells / mm3
Infants – 6 – 7 million cells / mm3
Normal life span of RBC – 120 days.
Variation in size ,shape of RBC
Anisocytosis - variation in size
Poikilocytosis - variation in shape
Erythropoiesis
Sites
Stages of development
Regulation
Factors essential
Site of Erythropoiesis
Mesoderm of the yolk sac in first 3 months of intrauterine
life ( Mesoblastic stage)
3rd and 4th of month of intrauterine life (Hepatic stage) :
Liver & Spleen
From the red bone marrow in rest of the intrauterine life
and post natal period (Myeloid stage)
Bone marrow
2 types – Red & Yellow
Functions
of red bone marrow (RBC, WBC & platelet
formation)
Redbone marrow in adults is present in flat bones
(membranous bones) like cranial bones, ribs, sternum,
vertebrae, pelvic bones and upper end of long bones like
femur and humerus
Pluripotent Hemopoietic stem cell
Stages of Erythropoiesis
Totipotetent/ Pluripotent Haemopoietic Stem
Cell
↓
Proerythroblast
↓
Early normoblast
↓
Intermediate normoblast
↓
Late normoblast
↓
Reticulocyte
↓
Erythrocyte
Stages in development of RBC
Terminology Cell size Nucleus Cytoplasm staining Mitosis
& Hb
Pluripotent 19-23 µ Very big,4-5 Basophilic, Absent Present
hemopoietic nucleoli
Stem cell
Proerythroblast 15-20 µ 3/4th of cell Basophilic, Absent Active mitosis
volume
Early normoblast 14-16 µ Decreases, Basophilic, Active mitosis
Nucleoli Absent
disappear
Intermediate 10-14 µ Decreases Poly Active mitosis
normoblast further chromatophilic,
Appearance of Hb
Late normoblast 8-10 µ Very small, cart Acidophilic Stops
wheel chromatin, (Eosinophilic),
Nucleus Hb content
degenerates Increases
“pyknosis”
Reticulocyte 7-8 µ Absent, Acidophilic, Absent
remnants of Present
RNA
Erythrocyte 7.2-7.5 µ Absent Acidophilic, Absent
Present
Early Normoblast
Intermediat Normoblast
Late Normoblast
Summary - Stages of Erythropoiesis
Cell size decreases
Cytoplasm increases in amount
Stainingreaction of cytoplasm changes
from deep basophilic to polychromatophilic
and finally to acidophilic
Nucleolusdecreases in size and finally
disappears
Regulation of Erythropoiesis
Erythropoietin
Androgens
Estrogen
Thyroxine, cortisol & growth hormone
Dietary factors
Erythropoietin / hemopoietin
Circulating glycoprotein
Released predominantly from renal tissue (85%) & 15%
from liver
Stimulus → Hypoxia , anemia & androgens
Decreased → estrogen, chronic renal disease
Dietary factors
Iron, manganese, copper, cobalt, nickel→ helps in
synthesis of heme
Proteins → globin formation
Calcium → increases iron absorption from GIT
Vitamin B12 , Vitamin C & folic acid → help in synthesis of
nucleic acid and maturation of RBC ( for conversion of
proerythroblast to mature RBC)
Vitamin B12 & folic acid
Folic acid deficiency occurs usually due to less dietary intake
Intrinsic factor (IF) - produced in the parietal / oxyntic cells of
the stomach
↓IF – decrease in Vitamin B12 (megaloblasts)
Vitamin B12 injection should be given
