Class 1 Red Blood Cells (RBCs)

Dr. Laxmikanta Say

ErythrocytesRed Blood Corpuscle

{RBC}

Definition - erythrocyte Greek “erythros” means “red” “kytos” for “hollow” “cyte” translated as "cell" in modern usage.

Circular, biconcave, non-nucleated disc.

Non-nucleated formed elements of blood which plays a vital role in transport of respiratory gases.

Colour – red, presence of pigment hemoglobin.

Normal count – 4.5-5.5m/cumm of blood

Size-7.2micron,Thickness-2.2 & 1micron.Shape-Biconcave disc (Dumbbell).Life span – 120days.Site of destruction-Reticulo Endothilial System.

Advantage of biconcave disci. Flexibility to RBC - easy folding of RBCs - squeeze through narrow

capillaries easily

ii. Allows alteration of cell volume - can withstand change in osmotic pressure - resist hemolysis

iii. Greater surface area - exchange of O2 , CO2 - diffusion of other substances

Actin, Spectrin - a contractile protein - arranged in fibrillar manner - maintains shape & flexibility of RBC membrane - specific blood group substance - “antigen”

Lack of spectrin - Hereditary Spherocytosis. - Fragile in hypotonic solutions.

How the shape is maintained ?

Composition62.5% - Water35% - Haemoglobin (29.5 ± 2.5 pg/RBC)2.5% a. Sugar – Glucose b. Lipids – Cephalin, Cholesterol & Lecithin c. Protein – Glutathion - a insoluble protein - acts as reducing agent - prevents damage of haemoglobin d. Enzymes of Glycolytic system; Carbonic anhydrase & Catalase e. Ions – Na+, K+, Ca2+ , PO43-, SO42-

Dimensions o RBC

Diameter –6.5 – 8.8 µm (7.4 µm)

Surface area- 140 µm2

Volume - 78 – 94 µm3 or fL(86± 8 µm3)

Normal Count:

At Birth; 6-7 million/µLMale – 5 -6 million/ µLFemale – 4.5 -5.5 million/ µLClinically 5 million/ µL taken as 100% RBC

Functions of RBCsTransport of oxygen from lungs to tissue. 97%-Oxyhemoglobin.

Transport of carbon dioxide from tissue to lungs.(33%).

Carbonic anhydrase forms bicarbonate from carbon dioxide and water. (67%).

Buffering action. Regulates acid base.

Blood group determination. ABO and Rh antigens.

Variations

Physiological cause of increase count.AgeSexHigh altitudeExercise (spleen)Emotion TemperatureMeal.Decrease-High atmospheric pressure in deep sea, pregnancy & sleep.

PathologicalINCREASE- POLYCYTHAEMIA. Primary, secondary, relative.

DECREASE- ANAEMIA. 1.Blood loss. 2.Deficiency. 3.Haemolytic. 4.Aplastic

PolycythaemiaPHYSIOLOGICAL -Age, Sex, High altitude, Exercise, Anxiety, Environmental temperature.

PATHOLOGICALi. Primary Polycythaemia - Polycythaemia vera - Erythremia - Malignancy of red bone marrow.ii. Secondary Polycythaemia - Chronic hypoxia - Emphysema, - Congenital heart diseaseiii. Relative Polycythaemia – Polycythaemia due to hemoconcentration - Burn, Dehydration.

Variations in Shape, Size & StructureSize - Microcyte, Macrocyte, Anisocyte.

Shape - Crenation, Spherocytosis, Sickle cell, Elliptocytosis, Poikilocytosis.

Structural change -Punctate basophilia – lead poisoning

Ring in R.B.C., Howell-Jolly bodies.

Haemoglobin

DefinitionoHaem & Globin

o It is red, oxygen carrying pigment found in the RBCs of vertebrates.

Molecular weight 64,450 dalton

Hemoprotein , accounting 90% of dry weight of mature cell.

o70 kg man contains 750gms of Hb.

oApprox. 6.25 gm(90mg/kg) of Hb are produced & destroyed in the body each day.

Globin makes it ‘species-specific’.

Globin of adult Hb contains high content of “Histidine” & “Lysin” & a small amount of “Isoleucine” .

Synthesis of haem occurs in Mitochondia.

Iron-protoporphyrin-IX

Other oxygen supplying Haemoproteins -Neuroglobin found inside brain-Myoglobin found in heart & skeletal

muscle, containing single polypeptide chain with heme moiety.

-Cytochrome-C seen in respiratory chain

HEMOGLOBIN STRUCTURE

Structure

Methine(=CH--) bridges , , , Side chain 1,3,5,8 Methyl(-CH) 2,4-Vinyl(-CH=CH2) 6,7-Propionic acid (-CH.CH2.COOH)

Formation of Hemoglobin

GlobinSynthesized from free ribosome.

Normal adult hemoglobin contains two identical α-chain & two identical β-chain.

Arranged in a configuration of “tetrahedron”.

Each polypeptide chain contains a heme, called “heme-pocket”. Thus one Hb. molecule contains four heme units.

-GLOBIN GENE FAMILY-141 amino acids-Chromosome no – 16- & (zeta)- embryonic globin-1st 8wks.

-GLOBIN GENE FAMILY-146 amino acids-Chromosome no -11 ( differs by 10 amino acids) (differs by 37 amino acids) (substitution in amino acid glycine or

alanine at codon position)

Hemoglobin Type

Name Component -

Like subunit

Adult A 2 2

A2 2 2 Fetal F 2 2

Embryonic Portland 2 2

(1ST 8 wks of I.U.life)

Gower 1 2 2

Gower 2 2 2

Abnormal H 4

Bart’s 4

SOME IMP. DEFINITIONS1.OXYHAEMOGLOBIN-Reacts with oxygen to form oxyhaemoglobin

and represented as HbO2.

Hb4 + O2 Hb4O2

Hb4O2 + O2 Hb4O4

Hb4O6 + O2 Hb4O8

-Affinity depends on pH, temperature and concentration of 2,3, diphospho-glycerate

(2,3 DPG) .HbO2 + 2,3-DPG Hb-2,3-DPG + O2

2.CARBAMINO-HAEMOGLOBIN-forms carbamino-haemoglobin CO2 + HbNH2 HbNH COOH

3.DEOXYGENATED HAEMOGLOBIN(REDUCED)

4.CARBOXY HAEMOGLOBIN or CARBON MONOXY HAEMOGLOBIN

-carbon monoxide react with haemoglobin.-it has >210 times affinity than oxygen.

5.METHAEMOGLOBIN-When reduced or oxygenated Hb exposed to various

drugs or oxidising agents, the ferrous (Fe++) is oxidised to ferric (Fe+++) and the compound is called methaemoglobin (HbOH).

Functions of Haemoglobin1. Respiratory:- Facilitate transport of oxygen from lungs to tissues.- Facilitates transport of CO2 from the tissues to lungs.2.Nutritive:-Conveys absorbed food materials, glucose, amino

acids, fatty acids, vitamins, electrolyte and trace metals.

3.Excretory: Transports metabolic wastes.4.Homeostasis for water, pH, and electrolyte

concentration: Excellent Buffering actions5.Regulation of body temperature6.Chemical for communication and protection7. Blood group determination. ABO and Rh

antigens.

CATABOLISM / FATE OF HEMOGLOBIN

RBCs are destroyed in “tissue-macrophage system” also known as “reticulo-endothelial system”.

-Kupffer cell of liver-Alveolar macrophages in Lungs-Osteoclasts in bone-Microglia in brain-Lymph nodes-Spleen-Littoral cells lining the blood sinuses in bone

marrow.

Types of Haemoglobin

Adult Haemoglobin

Age Amount of HbA

At 20 wks of intra uterine life

6% (rest Hb-F)

At Birth 20%

At 2 months(post natal)

50%

At 4 months(post natal)

90%

More than 1 year >99% (<1% Hb-F)

Glycosylated HaemoglobinHb-A1C

Normal conc. 3-6 %

Addition of sugar moiety to valine.

1-amino-1-deoxy fructose to -NH2 terminal of valine of β-chain of Hb-A1.

e.g, Diabetes mellitus (7.5--15%)

Foetal HaemoglobinDesignated as Hb - 22. β- Chain replaced by - chain (differs by 37 amino –acids)

Greater affinity for oxygen.Life span is less - 80 days.Hb-F predominates after birth to 1 year.(80%)

Persistence of Hb-F beyond 4-6 months, suspicious of disorder synthesis of Hb-A .(Thalassaemia)

APPLIED / HAEMOGLOBINOPATHIES

Hemoglobins with altered amino acid sequences that result in deranged function or altered physical or chemical properties.

CLASSIFICATION OF

HEMOGLOBINOPATHIES

1) STRUCTURAL GENE MUTATIONReplacement of a single amino acid

residue of HbA1e.g. Hb-S, Hb-M, Hb-C, Hb-D(Panjab)

2) REGULATOR GENE MUTATIONRate of synthesis of peptide chains , the

amino acid sequence remaining unaffected

e.g. - thalassemia, ß –thalassemia, ß, ß etc.

HAEMOGLOBIN-S Substitution of valine or lysine

residue for glutamic acid at position 6 in the ß-subunit of hemoglobin.

A point mutation.Polymerization of deoxy-Hb-S, forming

long fibrous precipitates and distorted to sickle shaped.

Sickle cells are more fragile .Vascular stasis and anoxic damage to

tissues.Protection from malaria.Increased incidence to Salmonella

infections.

PATHOPHYSIOLOGY OF SICKLE CELL ANAEMIA

SCAN

Pathogenesis of sickle cell disease

THALASSAEMIA

Heterogenous group of inherited disorders.

Genetic lesions leads to decreased synthesis of either alpha or beta - globin chain of HbA.

Types- -thalassaemia & -thalassaemia

-THALASSAEMIA

Synthesis of -chain repressed and synthesis of and -chain increased.

Hb-H (4)Hb-Barts (4)- Hydropes foetalis

Hb-Portland (2 2) - Hydropes foetalis

Hemoglobin H Disease

3 alpha-globin gene deletion(4) - most common among Asians - amount 10-20% - extremely high affinity for oxygen, - tissue hypoxia, - prone to oxidation, - precipitates of oxidised HbH form - moderately degree of haemolytic

anaemia

Hydrops Fetalis

all 4 alpha-globin gene deletionIn fetus excess gamma globin chains

form tetramers (Hb Barts - 4)very high affinity for oxygenNo oxygen delivery to tissuesFetal distress by 3rd trimester,IUD

resultsFetus – pallor, generalized edema,

massive hepatosplenomegalyIntra-uterine transfusion can save such

infants

-THALASSAEMIASynthesis of -chain repressed. Excess of -chains with -chains

produce Hb-A2 or with -chains produce Hb-F.

Severe anaemia of infancy or early childhood called as Cooley’s anaemia.

Mongoloid features & stunted growth.Icterus, SpenomegalyHypochromasia, polychromasia,

basophilic stipling,target cells++, nucleated cells.

X-ray – Hair-on-end appearance.

MISCELLANEOUS HbHb SHb CHb EHb D-PanjabHb G-PhiladelphiaHb HasharonHb IHb JHb Korel -BuHb LeporeHb MHb O-ArabHb Kansas

Thank You For Your Attention!