Pathway of Air in the Human Respiratory System

When we breathe, air follows a specific pathway through the respiratory system to reach the lungs, where oxygen exchange occurs. The pathway of air includes the following structures:

1. Nose/Nasal Cavity

• Air enters the body through the nostrils.
• The nasal cavity filters, warms, and moistens the air using tiny hair-like structures called cilia and mucus.
• This helps trap dust, microbes, and pollutants.

2. Pharynx (Throat)

• The air then moves into the pharynx, a shared passageway for both air (respiratory system) and food (digestive system).
• It directs air toward the larynx.

3. Larynx (Voice Box)

• The larynx contains the vocal cords and is responsible for sound production.
• A flap-like structure called the epiglottis prevents food from entering the airway by covering the windpipe while swallowing.

4. Trachea (Windpipe)

• The air passes into the trachea, a tube lined with cartilage rings to keep it open.
• The trachea further filters air using mucus and cilia.

5. Bronchi and Bronchioles

• The trachea divides into two bronchi—one for each lung.
• Each bronchus branches into smaller tubes called bronchioles, which distribute air within the lungs.

6. Alveoli (Air Sacs)

• The bronchioles end in tiny alveolar sacs, where gas exchange occurs.
• Oxygen from inhaled air diffuses into the blood capillaries, and carbon dioxide from the blood diffuses into the alveoli to be exhaled.

7. Blood Circulation and Gas Exchange

• Oxygen is carried by red blood cells to the body’s tissues.
• Carbon dioxide, a waste product, is transported back to the lungs and expelled through the same pathway in reverse order.

Summary of Air Pathway

Nose → Pharynx → Larynx → Trachea → Bronchi → Bronchioles → Alveoli (Gas Exchange) → Blood Circulation

This process ensures that oxygen reaches the body cells and carbon dioxide is removed efficiently.