Preksha Dhyana Perception of Breathing

Author(s): Mahapragna Acharya
Publisher: Jain Vishva Bharati

Page 26

The nose is the gateway to the respiratory tract. It filters, warms and moistens the incoming air. The interior of the nasal cavity is lined with mucous membranes. Dust and other fine particles and bacteria are caught in the stickly mucous. The mucous membranes also help to moisten the incoming air.
The trachea or wind-pipe lies in front of the aesophagus. it divides into two bronchi, one leading into each lung. The trachea with its two branches - the bronchi and their numerous branches the bronchial tubes and bronchioles, looks very much like an inverted tree. Each tiny bronchiole terminates in a cluster of minute air sacs, the alveoli which look like a miniature bunch of grapes.
Human lungs contain about three hundred million alveoli covering a total surface area of more than 90 square metres, enough to carpet a tennis court. This enormous surface area provides for an efficient exchange of gases. The two lungs are cone-shaped with the base resting on the diaphragm and the apex into the root of the neck. They are freely movable except at the roots. Their internal structure is a mass of branching tubes and air sacs. The alveoli has an extremely thin wall and is surrounded by a network of equally thin-walled capillaries. Gases diffuse back and forth between the alveoli and capillaries network, and the actual exchange of oxygen and carbondioxide occurs here.
Breathing
Respiration is the physical act of breathing in which air is alternately drawn into the lungs and expelled from them. Mostly this is an unconscious act that goes on throughout the day and even when one is asleep. Breathing includes two phases : inspiration or breathing in and expiration or breathing out.
When the pressure inside is greater than the pressure of the atmosphere, air is expelled from the lungs. When the outside pressure is greater than the inside, the air flows in. The mechanical power, required for the process of breathing is supplied by the
1. The estimate of the mumber of alveoli in an adult human body varies between
250 millions and 600 millions and surface area 70 to 90 square metres.
11