BLOOD CELL 1

Question 1

Characteristic Features of RBCs

Answer 1

Functional Morphology
* Non-nucleated
* The cytoplasm contains pigmented protein-haemoglobin.

Normal SIZE
o Diameter - 7.2 μm
o Thickness in the periphery is 2 μm and in the center 1 μm
o Surface area of 1 RBC=120– 140 μm2
o Volume is about 80 μm3

Normal shape
The red blood cells are circular, biconcave discs

Question 2

Advantages of Biconcave Shape

Answer 2

-The red cells quite flexible so that they can pass through the capillaries whose minimum diameter is 3.5μm
-The biconcavity provides greater surface area – Rapid gas exchange
-Biconcave shape is due to “SPECTRIN

Question 3

What is Rouleaux Formation

Answer 3

❖refers to the tendency of the RBCs to pile one over the other like a pile of coins.
❖The discoid shape and protein coating of red cells play a major role
❖does not occur in the normal circulation
❖Reversible phenomenon – promotes sedimentation of the RBC ( no nucleus)
❖Albumin- decreases rouleaux formation ❖Fibrinogen, globulin – increase rouleaux
formation.

Question 4

Normal Count of RBCs

Answer 4

At birth: 6–7 million/mm3.

Adult males:5 to 6.5 million/mm3 (average 5.5 million/mm3)

Females:4.5 to 5.5 million/mm3 (average 4.8 million/mm3).

Clinically, 5 million/mm3 is considered as 100%.

Question 5

Functions of Erythrocytes (RBCs)

Answer 5

• transport oxygen from lungs to the tissue with presence of haemoglobin in RBC
• Hb participate in CO2 transport from tissue to lungs and maintenance of acid base balance
• RBC contribute 50% of viscosity of blood
• Antigen on RBC membrane help blood grp classification

Question 6

Variations of RBCs

Answer 6

size:
microcytosis
macrocytosis

shape
Spherocyte
Elliptocytes
Sickle cell
Poikilocyte

count: increase, decrease

Question 7

Size

Answer 7

Microcytosis
volume of red cell is less than 80 μm3
Decrease in the size of RBCs occurs:
– In iron deficiency anaemia
– During prolonged forced breathing
– When osmotic pressure of the blood is increased.

Macrocytosis
volume of red cell is more than 94 μm3
Increase in the size of RBCs occur:
– In megaloblastic anaemia
– During muscular exercise
– When osmotic pressure of the blood is decreased.

Question 8

Variations in Shape of RBCs(4)

Answer 8

Spherocyte
When red cells assume spherical shape
✓ Hereditary spherocytosis

Elliptocytes
Oval shape with varying degrees of elliptical aberration
✓ Hereditary elliptocytosis
✓ Thalassemia
✓ Iron deficiency anemia.

Sickle cell
Drepanocyte is the red cell having sickle shape
✓ Sickle cell anemia.

Poikilocyte
This means red cells are of different shapes.
✓ Older cells are present in
circulation

Question 9

Increase in RBCs Count

Answer 9

Physiological
✓ High altitude (due to hypoxia)
✓ New-born
✓ After exercise
✓ After meal
✓ Excessive sweating & dehydration

Pathological
✓ Polycythemia vera
✓ Secondary Polycythemia:
▪ Congenital heart disease
▪ Lung diseases
▪ Chronic respiratory disorders
▪ Phosphorus and arsenic poisoning.

Question 10

Decrease in RBCs Count

Answer 10

Physiological
✓ Children have lower values than adults
✓ Women have lower values than men

Pathological
✓ Different types of anemia
✓ Haemolysis
✓ Bone marrow suppression
✓ Chronic blood loss
✓ Chronic kidney diseases

Question 11

Describe the structure of RBC

Answer 11

RBC membrane is a trilaminar structure having a bimolecular lipid layer interposed between the two layers of proteins

LIPID BILAYER
❖Provides an impermeable barrier between cytoplasm and external environment.
❖Helps to maintain a slippery exterior – RBC do not stick to the vascular endothelium.

INTEGRAL PROTEINS
* Band-3 protein - anion exchanger
* The glycophorins – modulate interaction between red cells and interaction of red cells to endothelium.

MEMBRANE SKELETON
▪ Spectrin - maintain cellular shape, provide structural support
▪ Ankyrin - membrane stability
abnormal ankyrin causes hereditary spherocytosis

Question 12

Red Cell Fragility

Answer 12

-The tendency of the cells to hemolyze
- Mechanical Fragility
Lysis of red cells due to red cell diameter is slightly less than the diameter of average capillaries.
- Osmotic Fragility
Lysis of red cells on exposure to different osmotic solutions. It assesses the integrity of red cell membrane.

Question 13

Osmotic Fragility

Answer 13

Osmotic fragility test helps diagnosis of anemia
-hypertonic(e.g. > 0.9% NaCl)
-isotonic (e.g. 0.9% NaCl, 5% glucose, 10% mannitol and 20% urea).
-hypotonic (e.g. 0.9% NaCl, 5% glucose, 10% mannitol and 20% urea).
Spherical – increased hemolysis Flat like sickle cells - decreased hemolysis.

Interpretation of Rate of hemolysis
❖ Hemolysis ↑ osmotic fragility ↑

Question 14

Normal Value and variation of osmotic fragility

Answer 14

Conditions Diminished Fragility
* Iron deficiency anemia
* Thalassemia
* Sickle cell anemia
* Obstructive jaundice
* Post-splenectomy

Conditions Increased Fragility
* Hereditary spherocytosis
* Congenital hemolytic anemia
* Other conditions in which spherocytes are found in the blood.

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Question 15

Haemoglobin (Hb)

Answer 15

❖ Red-coloured protein pigment
❖ 4 units, each unit consists of:
❖ Haem group: red pigment that contains iron in the ferrous form (Fe2+) + Globin: polypeptide chain

Question 16

Types of Haemoglobin

Answer 16

Four types of globin molecule (α, β, δ & γ)

Major adult haemoglobin(HbA)
2 α chains & 2 β chains (α2 β2)

Minor adult haemoglobin(HbA2)
2 α chains & 2 δ chains (α2 δ2)

Foetal haemoglobin (HbF)
2 α chains & 2 γ chains (α2 γ2)
Has a higher affinity for O2 than HbA

❖At birth, 2⁄3 of the Hb content is HbF & 1⁄3 is HbA ❖By 5 years of age, HbA > 95%, HbA2 < 3.5%, HbF < 1.5 %

Question 17

Haemoglobin Normal Values

Answer 17

Average: 15 g/dL
New-born(2 – 5 months) =17 – 23 g/dL
Toddler(3 – 10 years) =11 – 15 g/dL
Males=14 – 18 g/dL
Females=12 – 16 g/dL

Question 18

Functions of Haemoglobin

Answer 18

Transport of oxygen from lung to tissue
Transport of carbon dioxide from tissue to lung
Helps in regulation of acid-base balance
Gives red color to blood

Question 19

Haemoglobin Disorder

Answer 19

When Hb is abnormal (abnormal globin chain) – it cannot carry O2
✓ Thalassaemia - Defect in the synthesis of polypeptide chain α and β of HbA
✓ Sickle cell anaemia - Abnormal production of polypeptide chains (HbS)