Red blood cells, also known as erythrocytes, are biconcave discs that contain hemoglobin which transports oxygen and carbon dioxide throughout the body. Key functions of red blood cells include oxygen transport from the lungs to tissues and carbon dioxide transport from tissues back to the lungs. The document discusses normal red blood cell counts and dimensions in different age groups and gender. It also covers abnormal red blood cell shapes and conditions they are associated with, as well as factors that affect red blood cell sedimentation rate and hematocrit levels.

1. RED BLOOD CELLS

2. Thestudentwillbeableto:(MUSTKNOW)
 Give the dimensions of red cell and normal red
cell count in different age groups in males and
females.
 List the functions of red cells.
 Give the list of abnormal forms of red cells and
the common condition in which these
abnormalities are observed.
 Appreciate the importance of specialities of red
cell membrane.
 Understand the meaning of red cell fragility
and give the causes of increased and decreased
fragility of red cells.

3. Thestudentwillbeableto:(MUSTKNOW)
 Give the values of hematocrit in males and
females and common conditions of
variations in hematocrit.
 Explain the mechanism of erythrocyte
sedimentation rate (ESR), list the factors
affecting ESR, give the values of ESR in
males and females, and list the physiological
and pathological variations in ESR

5. ERYTHROCYTES
 The red blood cells are named as
erythrocytes as they appear red (erythros
means red) in a stained smear of peripheral
blood.
 Red cells are the major cellular elements of
blood and perform transport of oxygen from
lungs to tissues, and carbon dioxide from
tissues to the lungs.

7. Blood Components: Cells
 Erythrocytes
 Red Blood Cells (RBC)
 O2 & CO2 transport
 White Blood Cells (WBC)
 Immune defense
 Phagocytosis
 Platelets: clotting

9. FORMED ELEMENTS
 Red Blood cell
 Are disk-shaped and biconcave; no nucleus;
contains hemoglobin
 Live for about 120 days .
 Main component is the hemoglobin which is
responsible for 98.5% of the oxygen transported
in the blood
 6.9 – 7.5 µm in diameter(average=7.2)
 Function: transports oxygen and carbon dioxide

10. Why Hb Should be inside RBCs:
When Hb is free in the plasma, 3 % of Hb will leak
through capillaries into tissue spaces or glomerular
filtrate each time the blood passes through the
capillaries.
So, Hb must be inside red blood cells to remain in the
human blood.
The major function of red blood cells :Transport
hemoglobin, which carries oxygen from the lungs to the
tissues.

11. Another function
 1.RBCs contain carbonic anhydrase enzyme
which catalyzes the reversible reaction between
carbon dioxide (CO2) and water to form carbonic
acid (H2CO3).This reaction makes it possible for
the water of the blood to transport CO2 in the
form of bicarbonate ion (HCO3
-) from the tissues
to the lungs, where it is reconverted to CO2 and
expelled into the atmosphere as a body waste
product.
 2.The Hb is an excellent acid-base buffer , so
that RBCs are responsible for most of the acid-
base buffering power of whole blood.

12. Abundance of RBCs
 Erythrocytes account for slightly less than half the
blood volume, and 99.9% of the formed elements
 Hematocrit measures the percentage of whole
blood occupied by formed elements
 Commonly referred to as the volume of packed red cells

14. Structure of RBCs
 Biconcave disc, providing a large
surface to volume ration
 Shape allows RBCs to bend and flex
 RBCs lack organelles
 Typically degenerate in about 120
days.

15. Red blood cells specialisations
2) no nucleus
 extra space inside
3) contain haemoglobin
 the oxygen carrying
molecule
 250million molecules
/ cell
1) biconcave shape
increases the surface
area so more oxygen
can be carried

16. Figure 19.2
Figure 19.2 The Anatomy of Red
Blood Cells

18. RedBloodCell
 Diameter of each RBC is 7.2 µm(range6.9-
7.4µm)
 Thickness-in periphery is 2µm and in center is
1µm.
 Surface area of each RBC is 120-140µm2
 Volume is about 80µm3

19. AdvantagesofBiconcaveShape
 It renders the cells quite flexible so that they
can pass through capillaries(3.5µm)
 Biconcave shape increases surface area 20-
30%.
 Thus it allows easy exchange of gases.
 Biconcavity allows considerable alteration in
cell volume .So RBCs can withstand
considerable changes of Osmotic Pressure &
resist hemolysis.

20. Theshapesofredbloodcellscanchangeasthecellssqueezethroughcapillaries.
 Because the normal RBC has an excess of cell
membrane for the quantity of material inside,
deformation while passing through smallest
capillaries does not affect the membrane, so
the Red Cells do not rupture passing
through capillaries.

21. Life Span of Red Cells
Red cells usually live for 120 days.
Aged red cells are destroyed by tissue
macrophage system.
Life span of red cells can be measured by
injecting radioactive iron or RBCs tagged with
radioactive chromium (51Cr).
The tagged red cells lose radioactivity as they are
destroyed.
Complete disappearance of radioactivity gives
the life span of red cells.

23. Normal Counts
 At birth RBC count-6-7million/cubic m.m.
 In Adult male =5-6.5million/cubic m.m.of
blood(average=5.5million/cubic m.m.)
 In females =4.5-5.5 million/cubic mm
(average=4.8 million/cubic mm )
 Clinically a count of 5million/cubic mm is
considered as 100%

24. Variationinsize,shape&countsofRBCs
 Variation in size is called anisocytosis:
 Microcytosis i.e. In size of red blood cells
occurs in
- iron deficiency anaemia, thalassaemia
(MCV<80)
Macrocytosis i.e. In size of RBCs seen in
Megaloblastic Aneamia (MCV>95)

25. HypochromicMicrocyticRBC

26. MegaloblasticAnemia

27. Poikilocytes
 This means red cells are of different shapes.
Poikilocytosis is usually seen when older cells are
present in circulation .
Spherocytes
 When red cells assume spherical shape, are called
spherocytes. This is seen in conditions like hereditary
spherocytosis.
Elliptocyte
 When red cells assume oval shape are called
elliptocytes .
 Elliptocytosis occurs in hereditary elliptocytosis,
thalassemia and iron deficiency anemia.
VariationinshapeiscalledPoikilocytosis

28. Her. Spherocytosis:

29.  Elliptocytes i.e. elliptical shape of RBCs seen in
some aneamia

30. Sickle cell,i.e. crecent shape of RBCs
due to presence of HB S

31. Sickle Cell Disease:

34. Echinocyte (Burr cells)
 A “burr cell” or crenated red cell is an echinocyte .
Echinocytosis occurs in uremia and liver disease.

35. Dacryocyte (Tear Drop)
When the red cell assumes the appearance of
a tear drop, is called dacryocyte
Dacryocytosis occurs in myelofibrosis with
myeloid metaplasia, thalassemia

36. Keratocytes
 Keratocytes are red cells having a pair of
spicule.
 Keratocytosis usually occurs by mechanical
damage or by removal of a Hinz body by pitting
action of the spleen. ‘Hamlet cells’ and ‘bite
cells’ are also used to describe keratocytes

37. Schistocytes
Schistocytes are fragments of red cells . They
are smaller than red cells and they have sharp
angles and spurs.
Schistocytosis (red cell fragmentation) occurs in
thalassemia, mechanical stress (microangio-
pathic hemolytic anemia, cardiac hemolytic
anemia etc.), and thermal injury (severe burns).

38. Basophilic Stippling
This means presence of numerous basophilic granules
(coarse and dark-blue granules) in red cells .
This condition is called punctate basophilia.
It is typically seen in lead and other heavy metal poisoning.
It also occurs in thalassemia, megaloblastic anemia,
infections and liver disease.

39.  Sometimes in lead poisoning, Cabot’s ring
(ring shape or figure of 8) at the periphery of
red cells or Howell Jolly bodies (small nuclear
fragments appear in cytoplasm) are found in
erythrocytes.
 Nucleated red cells are seen in severe
hemolytic anemia.

41. Variations in counts
 Physiological factors
 Age- at birth 6-7 million/cmm of blood
 Sex- adult females =4.8million/cmm
adult males =5.5million/cmm
High Altitude- persons residing at mountains
(>10,000feet) have high RBC counts
7million/cmm because of hypoxic stimulation of
erythropoisis

42. Physiological in RBC
count
 After sleep
 In pregnancy- due to haemodilution
 At high barometric pressure

44. Polycythaemia-pathological
in RBC count above
7million/cmm
 Primary polycythaemia or polycythaemia
vera(PV)– malignancy of bone marrow
 Secondary polycythaemia-occurs due to state
of chronic hypoxia in the body such as: -
congenital heart diseases
 Chronic respiratory disorder like emphysema
 Phosphorus & arsenic poisoning

45. Polycythemia
 Description:
 an increase in the number of circulating
erythrocytes and the concentration of
hemoglobin in the blood; also known as
polycythemia vera, PV, or myeloproliferative
red cell disorder, polycythemia can be primary
or secondary

46. Polycythemia
 Etiology and Pathophysiology
a. Primary
 Neoplastic stem cell disorder characterized by
increased production of RBCs, granulocytes,
and platelets
 With the over production of erythrocytes,
increased blood viscosity results in congestion
of blood in tissues, the liver, and spleen
 Thrombi form, acidosis develops, and tissue
infarction occurs as a result of the diminished
circulatory flow of blood caused by the
increased viscosity

47. Polycythemia
 b. Secondary
 Most common form of polycythemia
 The disturbance is not in the development of red
blood cells but in the abnormal increase of
erythropoietin, causing excessive erythropoiesis
 The increase in red blood cell production caused
by increased erythropoietin release is a
physiologic response to hypoxia; hypoxia
stimulates the release of erythropoietin in the
kidney

50. Polycythemia
 Chronic hypoxic states may be produced by
prolonged exposure to high altitudes,
pulmonary diseases, hypoventilation, and
smoking
 The results of an increased RBC production
include the increased viscosity of blood,
which alters circulatory flow

51. Cell Membrane & Metabolism
Red Cell Membrane
 Red cell membrane is made up of three
major structural elements:
 Lipid bilayer
 Integral proteins and
 Membrane skeleton.

58. Hematocrit
 Percent of formed elements
Hematocrit
• Normal Hematocrit is around 45%,
depending on gender

59. Packed Cell Volume (PCV)
 Hematocrit represents the percentage of red
blood cells in blood (called Packed CellVolume
(PCV)
 1. A lower than normal hematocrit is
representative of a condition known as
anemia
 2. An abnormally high hematocrit is
representative of polycythemia
 Hematocrit “ for males: 40%-54%
(47%); Females: 38%-46% (42%)

60.  True Haematocrit = is calculated by
multiplying observed haematocrit by 0.98. it
is calculated because 2% of plasma is trapped
in between the cells.
 Body Haematocrit = is calculated by
multiplying the observed haematocrit with
0.87. it is calculated because of the fact that
haematocrit estimated from venous blood
whose haematocrit is greater than the whole
body.

62. MCV (Mean Corpuscular Volume)
 It refers to average volume
of single red blood cell.
 Normal value=80-100µm3
 one cubic micro meter is equal to one
famto letre(fl)
 When MCV is normal=RBCs
are termed Normocytes.
 When MCV =Microcytes
seen in IDA (<80µm3 )
 When MCV =Macrocytes
seen in Megaloblastic
Anaemia (>100µm3 )

63. Blood indices:
2. Mean Corpuscular Haemoglobin (M.C.H.):
Is an expression of average amount of Hb per cell
in picograms (pg =10-12gm).
-
Normal M.C.H.= 27-32 pg.
*
dlerqader74@yahoo.com

64. MCH(Mean Corpuscular Haemoglobin)
 It means average amount of Hb present in
each red blood cell
 In IDA - low
 HS and Megaloblastic Anaemia -high
<27 pg. Hypochromic anaemia(Iron deficiency).
* >32 pg. (Vit.B12 deficiency).

65. MCHC(Mean Corpuscular Haemoglobin
Concentration)
 It refers to the amount of Hb
expressed as percentage of the
volume of a RBC
 Normal value= 33.3%(range 32-36%)
 RBCs with normal value of MCHC are
called Normochromic.
 MCHC<30% = Hypochromic RBCs
seen in IDA,Thalassemia
 MCHC can’t be more than(36)%

66.  So RBCs can’t be Hyperchromic
 since RBC’s can’t hold the HB beyond the
saturation point.
 Whole enzymatic machinery of RBC’s after full
working can’t form HB more than 34% of the
volume of a RBC
 MCHC has greater clinical importance as it is
independent of RBC count & RBC’s size
 It is simply ratio of MCH/MCV ×100

67. C.B.C
 Haemoglobin - 15±2.5, 14 ±2.5 - g/dl
 PCV - 0.47 ±0.07, 0.42 ±0.05 - l/l (%)
 Haematocrit, effective RBC volume
 RBC count - 5.5 ±1, 4.8 ± 1 x1012/l
 MCHC - Hb/PCV - 32-36 - g/dl
 Hb synthesis within RBC
 MCH - Hb/RBC - 29.5 ± 2.5 pg/dl
 Average Hb in RBC
 MCV - PCV/RBC- 85 ± 8 - fl

70. Roulaeux Formation
 Is the tendency of RBC’s to pile one over
the another like a pile of coins.
 Albumin decreases the rouleaux
formation, while fibrinogen and
globulin & other products of tissue
destruction increases it.
 This is a reversible phenomina ,but it
promotes sedimentation of RBC;s
 It does not occur in normal
circulation,however within a blood
vessel in absence of significant flow &
when the blood is taken out the red cells
tend to form roulaeux.

71. ESR(Erythrocyte
Sedimentation Rate)
 Is the rate at which the red blood cells
sediment(settle-down) when the blood
containing an anti coagulant is allowed to
stand in a vertically placed tube. It is
expressed to m.m. at the end of 1st hour.
 Westergren’s Method normal value 0-15 mm
1st hour(M) 0-20mm1st hour (F)
 Wintrobe’s Method: 0-9mm 1st hr(M), 0-
20(increase with age)

72. Put anti-coagulated
blood in vertical tube,
then RBC will sink slowly
for its larger density.
ESR is expressed by RBC
sinking distance during
the first hour.
Measurement of ESR

74. ESR
 Has no specific diagnostic value.
 However ,raised level of ESR do suggest
presence of some chronic inflammatory
condition in body
 Estimation of ESR is more useful as a
prognostic test i.e. to judge the progress of
the disease in patients under treatment.

75. Factors affecting ESR
 Rouleaux formation- = ESR
,fibrinogen & proteins which
enters in plasma in
inflammatory and neoplastic
disease favours RF
 In size of RBC’s= ESR
 When no of RBC’s increased
the ESR is decreased & when
the no of RBC’s decreased(as
in aneamia) the ESR is
increased
 ESR increases when the
viscosity of blood is & vice
versa.
 Males =ESR is higher then
females
 Pregnancy=ESR is High
 New Born=ESR is low

76. The most important factor that determines ESR
is the extent of rouleaux formation by erythrocytes
Rouleaux formation is determined mainly by the nature of plasma. Increased
rouleaux formation occurs when plasma contains
increased amounts of fibrinogen (as in pregnancy)
and serum globulin (as in inflammatory diseases).
Red cell characteristics also affect rouleaux formation and therefore affect the ESR
too. Red cells with higher MCHC (mean corpuscular hemoglobin concentration) tend
to fall faster in plasma than those with normal or low MCHC. Poikilocytosis
(excessive variation in shape of the red cells) or anisocytosis (excessive variation in
size of the red cells) reduces ESR

78. Two well-known pathological causes of elevated ESR are
tuberculosis and rheumatoid arthritis. However, since ESR is
elevated in almost all inflammatory disorders and collagen
diseases, it has little diagnostic utility.
Its main utility is in prognosis, that is, prediction of the probable
course of a disease in an individual and the chances of recovery.
Thus, during a 6-month course of tuberculosis treatment, serial
measurements of ESR will indicate if the patient is improving. It
has similar use in certain malignancies, especially Hodgkin
disease.

79. Pathological variation of
ESR
ESR ESR
 Tuberculosis
 Malignancy
 Chronic infections
 All anemia's except Sickle
cell
 Collagen diseases.
 Polycythemia
 Decreased fibrinogen level
 Sickle Cell Anemia
 Allergic Conditions

80. APPLIED ASPECTS
Red Cell Fragility:
 The tendency of the cells to hemolyse
is called fragility of the cells.
There are 2 types of fragility:
 Mechanical
 Osmotic.

81. Mechanical Fragility
 Lysis of red cells due to mechanical stress and strain is called
mechanical fragility.
 Therefore, when red cells pass through capillaries and
splenic pulp, their membrane undergoes mechanical stress.
 On average, a red cell passes about three lakh times though
capillaries during its life span, which makes the cell more
fragile.
 Also, when red cells become older, the membrane becomes
rigid. Increased membrane stiffness and mechanical stress
make cell vulnerable to rupture.
 Red cell membrane defects increase mechanical fragility.

82. Osmotic Fragility
 Lysis of red cells on exposure to different
osmotic solutions is called osmotic fragility.
 It assesses the integrity of red
cellmembrane.
 The osmotic fragility test helps in the
diagnosis of anemia in which the physical
properties of the red cells are altered.
 This test detects whether or not the red cells
can easily be hemolyzed.
 .

83.  In an isotonic solution, the solution of equal
concentration as that of red cell content, the red
cells remain intact.
 Such a solution has same tonicity with that of
plasma. Examples are 0.9% NaCl, 5% glucose,
10% mannitol and 20% urea.
 When suspended in hypertonic solution, a
solution with more tonicity (> 0.9% NaCl), red cells
shrink due to loss of water from them by
exosmosis.

84.  Red cells absorb water by endosmosis, when
kept in hypotonic solutions, a solution with
less tonicity
(< 0.9% NaCl). Endosmosis results in hemolysis
due to swelling and rupture of the cells

86. Cell shrinkage or swelling：
Isotonic: cell neither shrinks nor swells
Hypertonic: cell shrinks (crenation)
Hypotonic: cell swells (lysis)

87. Properties of RBC
3. Osmotic
Fragility
：
The resistance of
RBC to hypotonic
solution.
0.8% 0.46% 0.34%
0.9% 
Normally, osmotic fragility begins at 0.45 to 0.50 and completes at 0.30 to 0.33

88. Interpretation: When the rate of hemolysis of red cells is increased, the
osmotic fragility is said to be increased, and when the rate of hemolysis
is decreased, the osmotic fragility is said to be decreased

89. Normal Value & Variations
Normally, osmotic fragility begins at 0.45 to 0.50 and completes
at 0.30 to 0.33.
Conditions of Diminished Fragility:
- Iron deficiency anemia
-Thalassemia
- Sickle cell anemia
- Obstructive jaundice
- Post-splenectomy
Conditions of Increased Fragility:
- Hereditary spherocytosis
- Congenital hemolytic anemia
- Other conditions in which spherocytes are found in the blood.

90. Metabolism of Red Cells
 Red cells have no nuclei, mitochondria and ribosomes.
Therefore, adequate synthesis of proteins and lipids does
not occur in red cells.
 Glucose is the primary fuel for red cells. Though enzymes
for glycolysis are present, enzymes for TCA cycle are
absent.
 ATP is formed by Embden-Mayerhoff pathway(EM
pathway).
 The HMP shunt provides NADPH.
 Glucose entry into the red cells occurs easily by facilitated
diffusion, which is independent of insulin action.
 Red cells depend mostly on glucose metabolism for their
energy supply.
 90% of glucose is oxidized by EM pathway and 10% by
HMP shunt.

91. Glucose Metabolism in RBCs
1- Glycolysis
2- Hexose mono-phosphate shunt (HMPS)

92. Glycolysis in RBCs
Glucose
2
NAD
2 NADH+H
2 ATP
2 Lactate
Glucose
1,3Disphosphoglycerate
2,3Disphosphoglycerate

93. EM Pathway
 Red cells metabolize glucose, usually by
anerobic glycolysis using EM pathway.
 Two ATP molecules are generated by
glycolysis through EM pathway.
 2, 3- DPG is produced in red cells. 2, 3- DPG
influences oxygen affinity of hemoglobin and
therefore, plays an important role in red cell
function.

94. Importance of glycolysis in red cells:
a) Energy production: it is the only pathway that
supplies the red cells with ATP.
haemolytic anaemia may occur due to an inherited
deficiency of glycolytic enzymes mainly pyruvate
kinase deficiency.
b) Reduction of methaemoglobin: glycolysis provides
NADH for reduction of met Hb by NADH-Cyto.b5
reductase
c) In red cells 1,3 Disphosphoglycerate is converted to
2,3 Disphosphoglycerate which binds to oxy Hb and
helps release of O2 to tissues.

95. HMP Shunt
The enzyme in the red cell, glucose-6-phosphate
dehydrogenase (G-6-PD) is the main enzyme for HMP
shunt.
 HMP shunt generates NADPH, keeps glutathione
in reduced state, which is a strong reducing agent
and prevents damage to the red cell.
 Therefore, G-6-PD deficiency interferes with red
cell functions and produce Hemolytic anemia

96. Importance of HMPS in Red cells:
 Red cells are liable for oxidative damage by H2O2
due to their role in O2 transport.
 In RBCs, H2O2 can cause both oxidation of iron in
haemoglobin (to form methaemoglobin) and lipid
peroxidation (increases the cell membrane fragility).
 The major role of HMS in red cells is the production
of NADPH, which protect these cells from oxidative
damage by reduction of glutathione that helps
removal of H2O2.

97. Non- Oxidative Phase
Oxidative Phase
Reversible
Non-Regulatory
Irreversible
Regulatory
6 moles of Pentose-P
5 moles of G-6-P
6 moles of G-6-P
6 moles of Pentose-P
12 NADP
12 NADPH +12 H
6 H2O
6 CO2

99. Role of NADPH+H in reduction of glutathione
G-S-S-G 2-GSH
2 GSH
+H2O2
G-S-S-G
+ 2 H2O
Glutathione
Reductase
Glutathione
peroxidase
NADPH+H NADP