Respiratory System 
Nose
Mouth
Larynx
Pharynx
Trachea
Lungs
It allows air to enter your body, then filters debris and warms and moistens the air. Your nose gives you a sense of smell and helps shape your appearance.
The lungs allow us to breathe. They bring oxygen into our bodies and send carbon dioxide out.
The function of the mouth in the respiratory system is to bring air into the lungs and moisten it.
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It's a hollow tube that lets air pass from your throat (pharynx) to your trachea on the way to your lungs. It also contains your vocal cords and is essential to human speech, so it's often called the voice box.
The pharynx, usually called the throat, is part of the respiratory system and digestive system. It carries air, food and fluid down from the nose and mouth. The pharynx is the site of common illnesses, including sore throat and tonsillitis.
Trachea's main function is to carry air in and out of your lungs. Because it's a stiff, flexible tube, it provides a reliable pathway for oxygen to enter your body.
Functions
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Gas Exchange – oxygen and carbon dioxide.
Breathing – movement of air.
Sound Production.
Olfactory Assistance – sense of smell.
Protection – from dust and microbes entering body through mucus production, cilia, and coughing.
Facts
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The lungs are the only organs that can float on water. ...
Your lungs are not sterile or germ-free, even in health. ...
The common cold can be caused by hundreds of different viruses. ...
Your nose is a filter, heater and a humidifier.