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.