Mechanism (Process) of Respiration

 MECHANISM of Respiration (process of RESPIRATION)

Respiration occur in two phases namely inspiration and expiration. 

• During inspiration, thoracic cage enlarge and lungs expand so that air enter the lungs easily. 

• During expiration, thoracic cage and lungs decrease in sizes, so that air leave the lungs easily.

• During normal quiet breathing, inspiration is active process, and expiration is a passive process. 

• Muscles involved in respiration can be classified into two groups:

I. Inspiratory muscles

👉 muscles involved in inspiratory movement are known as inspiratory muscles.

👉 primary inspiratory muscles (diaphragm, external intercostal muscles)

👉 accessory inspiratory muscles ( Sternocleidomastoid, scalene, anterior serrati, eleva tors of scapulae and pectorals)

II. Expiratory muscles

👉 primary expiratory muscles -internal intercostal muscles

👉 accessory excretory muscles-abdominal muscles. 

• Movements of thoracic cage

👉 movement of thoracic lid increases the anterior posterior diameter of thoracic cage. 

👉 movement of upper coastal series increases the anterior posterior and transverse diameter of the thoracic Cage, by pump handle movement and bucket handle movement. 

👉 movement of lower postal series increases the transverse diameter of thoracic cage by bucket handle movement. 

👉Flattening of diaphragm increases the vertical diameter of thoracic cage

• Movements of lungs:

👉 during inspiration, due to the enlargement of thoracic cage, lungs expanded. 

👉 during expiration, the thoracic cavity decreases in size, due to which lungs is compressed. 

Written by: RB Sah (MBBS)

Reference: K. Sembulimgan Physiology Book; Guyton and Hall Medical physiology