RED BLOOD CELL FORMATION
Dr. B.L. Mtinangi.
Department of Physiology
HKMU
November, 2015
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RED BLOOD CELL FORMATION
Rbc’s are circular, biconcave, disk-like,
dumbbell shaped, non nucleated living
cell.
 Mean Cell Volume (MCV) is the average
volume of each red cell (82-92cub
micron)
 Mean Cell Haemoglobin (MCH) is the
average Hb in each cell (27-32
picogram)
 Mean Cell Haemoglobin Concentration
(MCHC) this indicates the degree of
saturation of Rbc with Hb (32 to 38%)
RBC’s CONT.
During Anaemia MCHC is less, it is
known as hypochromic anaemia and
 If MCHC is normal it is normochromic
anaemia
Biconcave shape gives certain
advantages:
 Maximum surface area for gas diffusion
 Diffusion distance is minimised
 Rbc can mould their shape while
passing through narrow capillaries

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RBC’s FORMATION
There is some daily loss of Rbc’s
ie the average life span of Rbc’s is
about 120 days
 To keep the Rbc’s count normal or
to balance this loss
 Sufficient number of Rbc’s must
be produced daily

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FORMATION OF Rbc
Formation/generation
(ERYTHROPOIESIS) starts in the third
week of INTRAUTERINE life.
 Third week to third month
erythropoiesis occurs in the mesoderm
of the york sac
 Third month to fifth month it occurs in
the liver and spleen (HEPATIC PHASE)
 Fifth month onwards it occurs in the
red bone marrow
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HAEMATOPOIESIS
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FORMATION OF Rbc CONT.
Post natal (after birth) red
blood cell formation
(erythropoiesis) occur in the
RED BONE MARROW
Main sites for erythropoiesis:
 Ribs, vertebra, sternum,
cranium
 Pelvis. Shaft of the femur and
tibia
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BLOOD FORMING TISSUES
Myeloid tissues produces
Rbc,Wbc and Platelets.
 Lymphoid tissues include the
lymph node, thymus and spleen.
All produce Lymphocytes

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RBC maturation
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Rbc DEVELOPMENTAL
STAGES
Pluripotent stem cell ( Uncommitted
stem cell) develop into
 Committed stem cell into
Pronormoblast or Myeloblast or
Megaloblst or Lymphoblast
Pronormoblast (Proerythroblast) develop
into Early normoblast then to
Intermidiate normoblast then to Late
normoblast then into immature Rbc
(Reticulocyte) then within 2 to 3 days
develop into mature Rbc

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FORMATION OF Rbc CONT.

One committed stem cell
produces 16 mature Rbc1

10% to 15% of Rbc undergo
premature destruction during
development
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NORMAL VALUES
 Total
normal Rbc count:
men 4.5 to 6.4 mill/cumm
women 3.9 to 5.6
mill/cumm
 Normal Haemoglobin (Hb)
concentration:
men 13 to 17g/dl
women 11 to 16g/dl
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FACTORS INFLUENCING
ERYTHROPOIESIS
1. Erythropoietin.
 Is a hormone produced in
JuxtaGlomerular Apparatus(JGA)
in the macula densa (kidney)
 Is a glycoprotein with MW 36000
 Stimulate proliferation and
differentiation of erythroblast
 Stimulate Hb synthesis
 Promote Rbc maturation
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2. VITAMINS
VITAMIN B12
 Is essential for erythropoiesis ie it
stimulates erythropoiesis
 Present only in meat, fish and diary
products
 Absent in vegetables
 In the GIT it combines with the
intrinsic factor which protect &
transport it to the terminal ileum
 Absorbed in the terminal ILEUM
 Required for DNA and RNA SYNTHESIS
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3. FOLIC ACID
Folic acid is another vitamin that is
essential
 Stimulates erythropoiesis

Required for DNA and RNA
synthesis

Present in vegetables and fruits
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4.IRON
IRON:
 Found in the meat and vegetable
 Required for Haemoglobin synthesis
 Daily intake is about 10 to 20 mg
 5% to 10% of iron daily intake is
absorbed ie (0.5 to 2mg/day)
 2/3 of Iron is found in the Rbc
 It circulate in the blood as Transferrin
 Stored in the bone as Ferritin and
Haemosiderin
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Red Blood Cell Turnover
A summary of:

Bilirubin formation, circulation and
elimination
Senescent (old) Red blood cell
destruction
Hb is degraded to Haem & Globin
 Globin is reutilised as Amino Acid
 Haem an Iron component is degraded to a
porphyrin ring
 Porphyrin ring is converted to choleglobin

CONT
Choleglobin in the presence of an enzyme
haem oxygenase is converted to
BILIVERDIN
 Biliverdin in the presence of an enzyme
biliverdin reductase is converted to
BILIRUBIN
 Bilirubin is released into plasma

CONT
In the plasma Bilirubin is bound to
ALBUMIN and transported to the liver
 In the liver bilirubin is conjugated with
GLUCURONIC ACID to conjugated bilirubin
(bilirubin glucuronide)

CONT.
Conjugated bilirubin is transported to the
intestine through the bile duct
 In the intestine bilirubin is further
conjugated by the bacteria to
STERCOBILINOGEN
 Stercobilinogen is oxidized to stercobilin
after exposure to air in the feces

CONT
The reminder 5% is absorbed
(enterohepatic circulation) and
transported to the kidney as
UROBILINOGEN
 Urobilinogen is oxidized to UROBILIN after
exposure to air in the urine

ANAEMIA
Anaemia is defined as the reduction of:
 Haemoglobin
 Total red cell count
 Haematocrit (Packed cell volume – PCV)
According to age and sex
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CAUSES OF ANAEMIA
Causes could be due to:
 Nutritional deficiences, eg iron, folic acid,
vitamin B12 ect ects
 Excessive destruction of Rbc eg due to
malaria, sickle cell disease etc etc
 External/ internal bleeding
 Infestations eg hookworm
 Bone marrow failure
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Thank you