Blood

 Part4

# Oxygen transport ( Jb structure and breakdown, of molecules)

Haemoglobin is a large complex protein containing a large complex protein, globular protein ( globin ) and its pigment, iron containing complex called Haem.

Each haemoglobin molecule contain four atom of iron.

As each  atom of iron can combine an oxygen molecules , this means that a single Hb molecules can carry upto four molecules of oxygen. When all four oxygen binding sites on a Hb molecules are full . It is described as saturated Hb binds to oxygen to form oxyhemoglobin .

Haemoglobin + O2 _____ Oxyhemoglobin

Hb + O2 _______ HbO

Blood which is O2 is bright red  because of high level of HbO blood with lower oxygen level is that bluish in colour.

The association of oxygen with Hb is a loose one so that oxyhemoglobin release it's O2 readily, specially under certain conditions such as ____

Low pH

Low O2 level

Temperature

# Control of erythropoiesis

The number of blood cells remain constant, which they destroy. The primary stimulus to increased erythropoiesis is Hypoxia i.e is deficient O2 supply to blood cells.

This occurs when ______

 The O2 carrying capacity of blood is reduced by example:- Haemorrhage or excessive Erythrocytes breakdown ( Haemolysis ) .

 Hypoxia increases Erythrocytes formation by stimulating the product of the hormone Erythropoietin mainly by the kidneys.

 

Erythropoietin stimulates an increase in the production of proerythroblast and the release of increased number of reticulocytes into the blood. This increases the O2 carrying capacity of blood and reverse tissues hypoxia.

# Destruct of Erythrocytes or RBC 

 The life span Erythrocytes is about 120 days and their breakdown or Haemolysis is carried out by phagocytic reticuloendothelial cells, these cells are found in many tissues by the main sites of Haemolysis are the spleen  (graveyard of RBC ) , bone marrow and liver.

As Erythrocytes ages their cell membrane become susceptible to Haemolysis is retained in the body and reused in the bone marrow to form new Hb molecules.

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