A seminar presentation on Haemoglobin

Haemoglobin (abbreviated as Hb or Hgb) is the red, oxygen carrying pigment in the red blood cells of the vertebrates.

NORMAL VALUES OF Hb in BLOOD:

NEW BORNS: 18-22 gram/decilitre

At 3 MONTHS: 14- 16 gram/decilitre

3 MONTHS TO 1 YEAR: 13- 15 gram/decilitre

ADULT MALES: 14- 16 gram/decilitre of blood

ADULT FEMALES: 12- 14 gram/decilitre of blood

WHY HAEMOGLOBIN IS ENCLOSED INSIDE THE RBC:

In some lower animals Hb circulates as free protein in the in the plasma, but not in humans. When it is free in the plasma of human being, about 3% of it leaks through the capillary membrane into the tissue spaces or through the glomerular membrane of the kidney into the glomerular filtrate, each time blood passes through the capillaries. Therefore for Hb to remain inside the blood stream, it must exist inside the RBC.

Haemoglobunuria is the condition in which free Hb present in the plasma is excreted through the kidney into urine. Under normal conditions 100- 150 mg of free Hb is released from red cell destruction, which is normally bound to the haemoglobin-haptoglobin complex which cannot pass through the urine. If Hb in the plasma exceeds this amount then the Hb is excreted in the urine. Causes of Haemoglobinuria:

(i) Strenuous exercise

(ii) Mismatched blood transfusion

(iii) Blackwater fever

(iv) Paroxysmal Nocturnal Haemoglobinuria

(v) Hypotonicity of plasma

(vi) Thermal or chemical injuries.

If Hb remains outside the RBC the blood viscosity will rise (normal 4.7). The colloidal osmotic pressure will rise from 30 to 100 mmhg. While passing through the kidney haemoglobin will be precipitated, blocking the kidney tubules causing renal shutdown (Acute kidney failure).

Each RBC contains approximately 29 pg of haemoglobin and there are about 30 trillion RBC in the blood, so a total of 900 grams of haemoglobin is present in the blood of an adult man. 0.3gram/hour is formed and destroyed daily.