Mechanism of breathing

Respiration is a multi-step process which includes

1-Breathing

2-External respiration

3-Internal respiration or Tissue respiration or Cellular respiration 

Breathing is inhalation and exhalation of gas. Exchange of gases from alveoli to transport medium is EXTERNAL RESPIRATION. Breathing is totally mechanical process

Today our topic of discussion is 

MECHANISM OF BREATHING:

As we know breathing include inspiration and expiration. How this inhalation and exhalation occur?

If we want to bring atomospheric air inside our lung then we have to make the pressure difference. Thoracic cavity consist sternum ventrally,vertebral column in  dorsally  and ribs in lateral side and diaphgram in lower side. Spaces between ribs are knoen as Intercostal space in which intercostal muscles are present. 

According to boyles law Volume has inverse releation with pressure mean if we want to bring air inside the lung then we have to increase the volume of thoracic cavity so pressure inside the lungs decreases and air from outside come inside the lung

To increase the volume of thoracic cavity two things occur. The first thing is the contraction of diaphgram(Phrenic muscle) it contribute 75% in increasing the volume. The second thing that occur is the contraction of External intercostal muscle that contribute 25% in increasing the volume of thoracic cavity. Due to contraction of external intercostal muscle ribs moves upward and outward. Diaphgram is the skeltal muscle. As we discuss that muscle contraction occurs in inhalalation. Muscle contaction needs ATP so inhalation is the active process

Reverse process occur in exhalation. Muscle relaxes due to which volume decreases and pressure increase as a result air moves outside. It is a passive process as no ATP  used because muscle relax