Question

Describe the mechanism of inspiration and expiration in man.

Answer 1

Inspiration (breathing in) and expiration (breathing out) processes are important for supplying tissues with oxygen and extracting carbon dioxide from the body. Inspiration takes place by active muscle movement, such as the diaphragm, while expiration appears to be inactive, until it is induced.

Complete step by step answer: The breathing (respiration) process is split into two different steps, inspiration (inhalation) and expiration (exhalation).
The diaphragm contracts and pulls downwards during inspiration, while the muscles between the ribs contract and pull upward. This raises the thoracic cavity size and reduces inside pressure. Water floods in and covers the lungs as a result.
The diaphragm relaxes after expiration, and the thoracic cavity thickness reduces, while the pressure inside it increases. The lungs compress and air are squeezed out as a result.
In response to changes in pressure , air flows in and out of the lungs. When the air pressure falls below the atmospheric pressure within the alveolar spaces, air enters the lungs (inspiration) when the larynx is open; when the air pressure within the alveoli exceeds the atmospheric pressure, air is blown (expiration) from the lungs. In proportion to the degree of the pressure difference, the passage of air is fast or sluggish. Since air pressure stays relatively stable, flow is determined by how far the pressure inside the lungs raises or decreases above or below atmospheric pressure.
Fluctuations of alveolar pressure are caused by lung expansion and contraction, arising from stress and relaxation of the chest and abdominal muscles. The room enclosing lung air is transiently expanded by each slight increase in expansion. Thus, there is less oxygen in the lungs per unit of volume and pressure drop.
A variation in air pressure is produced between the atmosphere and the lungs, and air flows in until a higher lung volume is returned to equilibrium with ambient pressure.
The thickness of the chest and lungs reduces as the muscles of inspiration contract, the lung air is transiently squeezed, the pressure increases above ambient pressure, and the flow into the atmosphere results before the pressure balance at the initial lung volume is achieved. This, then, is the series of events during each natural respiratory cycle: changes in lung volume due to variations in pressure, resulting in air passage into or out of the lung, and the formation of a new lung volume.

Note: Breathing is a physiological mechanism which plays an important role in the circulation of carbon dioxide removal and oxygen supply. A number of studies show that, with advancing age, there are negative changes in the respiratory system. Deep and steady breathing by yoga can be effective in calming down these changes; it can also alleviate stress, anxiety , post-traumatic stress, chronic pain and depression.