Answer:
Respiratory system in humans includes a set of organs that allows a human being to breath and exchange gases throughout the body. It includes organs and tubes like nasal passage, larynx, trachea, bronchi, alveoli and lungs. The air enters the human body through two nostrils, then the air enters the nasal cavity.
The next structure to contact air after it passes from the nose to the nasal cavity is called as pharynx. It mainly directs the flow of air towards the lungs, where the oxygen replaces the carbon dioxide.