Preksha Dhyana Human Body Part 2

Author(s): Jethalal S Zaveri
Publisher: Jain Vishva Bharati

Page 13

exhausted. Worst of all, our resistance to disease is reduced drastically and we develop greater susceptibility to germs and infections. Correct breathing, by ensuring complete ventilation of the lungs, immunizes us against diseases like T.B. In the following paragraphs we shall see how this can be done.
The Process of Breathing
The lungs themselves have no muscles and hence play only a passive role in breathing. The mechanical power required for the process of breathing is supplied by (a) the raising and lowering of the diaphragm, (b) the contraction and expansion of intercostal muscles and (c) raising and lowering of the upper part of the thorax called clavicle or collar bone. A slight vacuum in the lung compartment enables the lung to expand and collapse with each inhalation and exhalation respectively.
At the start of a breath, the pressure inside the lungs is the same as the outside air-pressure (760 mm. of mercury). Then the intercostal muscles contract, moving the rib-cage upwards and outwards and at the same time the diaphragm contracts and moves downwards. The size of the chest cavity is thus increased and the inside pressure falls by 2 or 3 mm, of mercury. To equalise the pressure-difference, the air rushes into the lungs. Inhalation ends with the relaxing of the diaphragm and the intercostal muscles, reducing the chest volume. Inside pressure rises by about 3 mm. and forces used air back into the atmosphere.
The fresh air inhaled in the alveolit has an oxygen tension of 100 mm. and very little carbon dioxde, while the blood in the capillaries arrive with an oxygen tension of 40 mm. and carbon dioxide tension of 46 mm. To establish equi
1. The estimate of the number of alveoli in an adult human body varies between 250 millions to 600 millions. Total area of the surface of all alveoli is estimated to be 750 sq. ft. or 70 sq. metres, equivalent to the area of a tennis court.