The respiratory system that one draws in the oxygen from the air and discharges carbon dioxide, the byproduct of the process of metabolic function. It comprises of the nose, throat, mouth, windpipes, bronchi, bronchioles and the lung.

Air goes into your body when you breathe via the nose or mouth. Your nose has hair that blocks dust and other small particles from being inhaled into your system. Secondly, as it goes into the mouth it is warmed and it humidifies the air.
 

• It then goes through your throat as a passage to both your stomach and your lunges. After that it passes into the larynx or the voice box situated at the bottom of the throat. The larynx also comprises vocal cords that vibrate to produce sound.
  The last bronchus or the trachea lies below the larynx.
   
• Bronchi branch into progressively tiny tubes known as bronchioles. Air sacs, which are called alveoli, are very small and they mark the end of bronchioles. Capillaries form a network that surrounds the alveoli.
   
• Oxygen comes out of the air at the alveoli and enters the blood. The carbon dioxide is a by-product from the process of the oxidation of fuel and gets through from the blood to the air. From there, it drains into the veins that deliver oxygenated blood to the heart and is pumped to all parts of the body.
   
• Carbon dioxide enriched air goes out in the opposite way: via the lungs from the trachea through the larynx, the throat, your nose/mouth, bronchioles, and bronchia.
   
• The respiratory system is under the control of brain. Your lungs will actually expand or contract as the signals are sent by the brain to the muscles in the chest. Your rib muscles and the diaphragm contract, thereby drawing air into the lungs. The suction leads to space vacuum in your chest cavity, thus sucking air to the lungs.
  Upon inhalation, your diaphragm contracts and your rib muscles relax.