Lungs and gas exchange

Lungs and gas exchange

The primary function of the lungs is to provide oxygen to the tissues and remove carbon dioxide to outside. Respiration includes two phases:  (i) inspiration  (ii) expiration

Inspiration means supply of oxygen from the atmosphere to the tissue space through respiratory tract and blood.

Expiration means transport of carbon dioxide from the tissue space to atmosphere through respiratory tract and blood.

The respiratory system is made of                                          

(i)                 Lungs: gas exchanging organ                         

(ii)               Chest wall & respiratory muscle→ increase & decrease the size of the thoracic cavity

(iii)              Areas in the brain → control the muscles

Alveoli AND Respiratory Zone

•      Polyhedral in shape and clustered like units of honeycomb.

•      ~ 300 million air sacs (alveoli).

–     Large surface area (60–80 m²).

–     Each alveolus is 1 cell layer thick.

•      Total air barrier is 2 cells across (2 mm).

•      Respiratory Zone: Region of gas exchange between air  and blood.

–     Includes respiratory bronchioles and alveolar sacs.

–     Must contain alveoli.