Structure of Lungs

Lungs are respiratory organ.

Location – thoracic cavity.

At the time of birth, the lungs are pinkish in color because they are filled with air and blood.
After the human grows, they becomes blackish due to pollutants. 

Lungs are protected by bony skeleton, called rib cages.

Lungs are also protected with the help of coverings, called pleura.

Structure of Lungs

The lungs are made up of alveoli cells around 750-800 millions.
 

Between these two pleura layer a cavity exits, known as pleura cavity that is filled with pleural fluid.

 
Pleural layer and pleural fluid are protect the lungs from mechanical shocks and absorbing shocks. These also provide friction-less movement.

 
The cells of the body needs energy for all their metabolic reaction/activities. Most of this energy is derived from chemical reactions, which can only takes place in the presence of oxygen. The main waste product of these reactions is carbon dioxide. The respiratory system provides the route by which the supply of oxygen present in the atmosphere entire body and it provides the route of excretion for carbon dioxide.
 

Alveoli 

There are two type of alveoli cells.

 
Type 1 – Compose with simple squamous epithelium that helps in diffusion of gases.

 
Type 2 - Compose with simple cuboidal epithelium that secretes surfactant.