52
J. Kumar V. and K. A. Reddy
saturation in blood. Patients undergoing surgery or recovering after surgery must be
monitored for the oxygen saturation in blood.
3.2 Blood and Its Composition
Nutrients and oxygen for all the cells of the body are carried by blood. Blood also
transfers waste from all the cells of the body to waste disposal centres of the body.
Blood is composed of plasma (55%), red blood cells (RBCs in short form and known
as erythrocytes, 43%), white blood cells (termed as leukocytes, 1.5%), and platelets
(called thrombocytes, 0.5%). Nearly 90% of plasma is made of water with some
proteins and other chemicals dissolved in it. RBCs are mainly made of haemoglobin
molecules that responsible for the transport of oxygen to various other cells of the
body [4]. Typically, each mm
3 of blood contains approximately six million RBCs
and each RBC is made of about 280 million haemoglobin molecules. Haemoglobin
concentration in whole blood lies in the range: 134 gL
−1 and 173 gL
−1 [5]. The
absorption spectrum of the natural chromophore contained in the haemoglobin
depends on the number of oxygen molecules attached to a molecule of haemoglobin.
Haemoglobin without any oxygen molecule (Hb) absorbs most of the visible light
except in the dark blue region, and hence blood in the veins that has carbon dioxide
and lacks oxygen has the colour ‘dark blue’. If the haemoglobin carries oxygen
(HbO) then the natural chromophore absorbs light at all other wavelengths in the
visible spectrum except the red wavelength. That gives the bright red colour to the
arterial blood which is rich with oxygen. Blood is circulated throughout the body by
the systemic and pulmonary circulation system [6].
3.3 Systemic and Pulmonary Circulation
The flow of arterial blood, the replenishment of oxygen and exhaling of carbon
dioxide are controlled by the cardio-pulmonary system, comprising: (i) the heart,
(ii) the lungs and (iii) the blood vessels (arteries, veins and capillaries). Arteries
(except the pulmonary artery, which carries oxygen-depleted blood to the lungs for
replenishment of oxygen) carry oxygenated blood from the heart to all parts of the
body. Arteries terminate into capillaries and the blood in the capillaries provides
oxygen and nutrients to the cells and picks up the waste including carbon dioxide
from the cells. The capillaries terminate to small veins and the small veins lead to
bigger veins and the blood returns to the right atrium of the heart. The returned
venous blood then passes to right ventricle and gets pushed through the pulmonary
artery to the lungs. In the lung capillaries, the exhale of carbon dioxide and infusing
of oxygen takes place and the oxygen-rich blood from the lungs returns through the
pulmonary vein to the heart, thus completing one cycle.
J. Kumar V. and K. A. Reddy
saturation in blood. Patients undergoing surgery or recovering after surgery must be
monitored for the oxygen saturation in blood.
3.2 Blood and Its Composition
Nutrients and oxygen for all the cells of the body are carried by blood. Blood also
transfers waste from all the cells of the body to waste disposal centres of the body.
Blood is composed of plasma (55%), red blood cells (RBCs in short form and known
as erythrocytes, 43%), white blood cells (termed as leukocytes, 1.5%), and platelets
(called thrombocytes, 0.5%). Nearly 90% of plasma is made of water with some
proteins and other chemicals dissolved in it. RBCs are mainly made of haemoglobin
molecules that responsible for the transport of oxygen to various other cells of the
body [4]. Typically, each mm
3 of blood contains approximately six million RBCs
and each RBC is made of about 280 million haemoglobin molecules. Haemoglobin
concentration in whole blood lies in the range: 134 gL
−1 and 173 gL
−1 [5]. The
absorption spectrum of the natural chromophore contained in the haemoglobin
depends on the number of oxygen molecules attached to a molecule of haemoglobin.
Haemoglobin without any oxygen molecule (Hb) absorbs most of the visible light
except in the dark blue region, and hence blood in the veins that has carbon dioxide
and lacks oxygen has the colour ‘dark blue’. If the haemoglobin carries oxygen
(HbO) then the natural chromophore absorbs light at all other wavelengths in the
visible spectrum except the red wavelength. That gives the bright red colour to the
arterial blood which is rich with oxygen. Blood is circulated throughout the body by
the systemic and pulmonary circulation system [6].
3.3 Systemic and Pulmonary Circulation
The flow of arterial blood, the replenishment of oxygen and exhaling of carbon
dioxide are controlled by the cardio-pulmonary system, comprising: (i) the heart,
(ii) the lungs and (iii) the blood vessels (arteries, veins and capillaries). Arteries
(except the pulmonary artery, which carries oxygen-depleted blood to the lungs for
replenishment of oxygen) carry oxygenated blood from the heart to all parts of the
body. Arteries terminate into capillaries and the blood in the capillaries provides
oxygen and nutrients to the cells and picks up the waste including carbon dioxide
from the cells. The capillaries terminate to small veins and the small veins lead to
bigger veins and the blood returns to the right atrium of the heart. The returned
venous blood then passes to right ventricle and gets pushed through the pulmonary
artery to the lungs. In the lung capillaries, the exhale of carbon dioxide and infusing
of oxygen takes place and the oxygen-rich blood from the lungs returns through the
pulmonary vein to the heart, thus completing one cycle.