Pulmonary Ventilation: Inhalation and Exhalation | Biology Hubspot - Definition and Examples of Biology Terms

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Saturday, February 2, 2019

Pulmonary Ventilation: Inhalation and Exhalation


What Is Pulmonary ventilation? 

Pulmonary ventilation is also known by the more common term namely breathing. In this process, the alternating pressure differences generated by contraction and relaxation of respiratory muscles causes the air exchange between alveoli of the lungs and atmosphere.
The amount of air exchange and effort required for breathing is also affected by the other three factors viz alveolar surface tension, compliance of the lungs and airway resistance.

Pressure Changes During Pulmonary Ventilation? 

The air moves into and out of the lungs due to the air pressure difference between the inside of the lungs and outside the environment.
When the air pressure inside the lungs is lower than the air pressure outside the environment air rushes into the lungs(inhalation) and when the air pressure difference is in opposite direction air moves out of the lungs(exhalation).
Let's explain this in detail one by one
Inhalation 
The process of breathing in is known as inhalation, it is also known as inspiration. For the process of inhalation to occur the air pressure inside the lungs must be lower than the air pressure outside the environment. This condition (air pressure lower inside the lungs) is achieved by expanding the lungs.
The two important muscles that are involved in expanding of the lungs during inhalation are diaphragm and external intercostals.
  1. Diaphragm: The dome-shaped diaphragm contracts during inhalation. The contraction changes its structure from dome-shaped to flatten which results in a larger thoracic cavity and more space for the lungs.The Contraction of Diaphragm accounts for about 75% of the air to enter into the lungs.
  2. External Intercostals: The external intercoastal is responsible for uplifting the ribs during inhalation which results in an increase in the volume of the chest cavity. This increase in volume leads to a decrease in intra-alveolar pressure, creating a pressure lower than atmospheric pressure.The Contraction of external intercostals accounts for about 25% of the air to enter into the lungs.

Exhalation 

The breathing out called Exhalation (expiration) also occurs due to the air pressure difference between inside the lungs and outside the environment.But the air pressure difference in this process is in opposite direction in contrast to inhalation.
The exhalation is a passive process during Quiet breathing because no muscular activity is involved in it, as it results due to the elastic recoil of the chest wall and lungs both of which have an inherent tendency to recoil back after they are stretched.

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