Erythrocytes

Erythrocytes or Red blood cells

Red blood cells are the most numerous blood cells, they comprise about 99% of all blood cells.

Shape

Erythrocytes are circular bi-concave, non-nucleated (mature erythrocytes has no nucleus), slightly concave on top and bottom.

Diameter

7-8 micrometer in diameter.

Thickness

2micrometer thickness at periphery 1micrometer in centre.

Number of Red blood cells

In Males; 4.8 to 5.4 million/mm3 of blood

In Female; 4.5 to 5 million/mm3

Erythrocytes are 700 times more numerous than WBCs.

And 17 times more numerous than platelets.

Components of Erythrocytes

Main components of erythrocytes is pigmented protein Haemoglobin.

Haemoglobin (Hb)

Haemoglobin is an O2 carrying globular proteins.

Plasma membrane of RBCs encloses haemoglobin which is synthesized before loss of nucleus.

More than 90% of weight of erythrocytes consists if Hb.

 Hb occupies about 1/3rd of the total cell volume.

Each RBC contains about 280 million Hb molecules.

Composition of Haemoglobin

Hb molecule consist of 5% heme and 95% globin.

Structure of Haemoglobin

Hb molecules consist 4 protein chains and 4 heme group.

1. Polypeptide chains

Each chain consist of protein called globin. Globin is bound to one heme and provide nutrient to the heme.

2. Heme group

Heme group is red pigment molecule containing one iron atom, which gives blood its colour.

A heme group containing carbon, nitrogen and hydrogen atoms, with single Fe2+ ion at center.

Each haemoglobin can bind to four oxygen molecules.

Normal Haemoglobin Level

Normal Values of Haemoglobin;  12-17g/dl

In Adult males; 14-16.5 g/100ml of blood

In Adult females; 12-15 g/100ml of blood

In Infants; 14-20g/100ml of blood

Heme formation take place in Mitochondria.

Globin formation, polypeptide chain of globin are produced on ribosome.

Forms of Haemoglobin

1. Oxyhaemoglobin

2. Deoxyhaemoglobin

Function of Haemoglobin

1. Haemoglobin transport O2 from lungs to body tissue.

2. Hb Carries waste CO2 from tissue to the lungs.

3. By removing CO2, Hb help to maintain stable acid-balancing blood.

4. Colour of blood (arterial) is due to oxygenated Hb called oxyhaemoglobin, and bluish appearance in vein due to absence of oxygen is called deoxyhaemoglobin.

5. It Buffers the blood pH 

6. Maintaining homeostasis environment in body.