Gaseous Exchange in Human

 

Gaseous Exchange in Human

In humans and other higher animals the exchange of gases is carried out by the respiratory System.

  The respiratory system is divided into two parts.

(A) Air passage way      (B) The lungs 

(A)  Air passage way:
The air passage way consist of the parts through which the outside air comes in the lungs
And after the exchange of gases it goes out. This passage way of air consists of following parts.

1- The nasal cavity:
The nose encloses the nasal cavity. It opens to the outside through the openings called the
Nostrils.
2-Pharynx:
The nasal cavity opens into the pharynx by means of two small openings called internal
Nostrills.Pharynx is a muscular passage and is common to both food and air. It extends to the
Opening of the esophagus and the larynx. The air goes from the pharynx into the larynx.   
3-Larynx:
The larynx is a box, made of cartilage. It is present between pharynx and trachea. It is also called the voice box.
4- Trachea:
Larynx continues to the trachea, which is also called the wind pipe. It is about 12 cm long tube
This lies in the front of esophagus.
5- Bronchi:
On entering the chest cavity, the tracheas divided into two smaller tubes called bronchi.
6- Bronchioles:
The bronchi continue dividing in the lungs until they make several fine tubes called bronchioles.
7- Alveolar duct:
The bronchioles progressively lose the cartilages as the become narrower. The bronchioles end as fine tubes called the alveolar duct.
8-Alveoli:
Each alveolar duct opens into a cluster of pouches called alveoli.