Explain the human respiratory system?

• Respiratory system is responsible for the process of respiration. It involves exchange of gases, i.e, oxygen and carbon dioxide between body and surrounding. The body can't store oxygen, so, it is vital process and it is occurs all the time.
• The body takes up oxygen and passes it to whole body through blood.
• Respiratory system is divided into 2 major parts, upper respiratory tract and lower respiratory tract.  
• Upper respiratory tract is composed of nose, pharynx and larynx.

Nasal cavity traps the dust particles.  Air passes to lungs through pharynx, and larynx is essential for speech

• Lower respiratory tract is composed of the trachea, the lungs, and bronchioles including alveoli.
• Trachea is the main pathway to lungs.  Lungs are main site of gaseous exchange, they gives oxygen to capillaries and exhale carbon dioxide, Bronchi supply the lungs with air.  Bronchioles are the branches of bronchus.  They further branches into primary and secondary bronchioles.  And they finally terminate into alveoli.  Diaphragm contracts and relaxes to allow air into the lungs.