Question

Where does gaseous exchange take place during respiration in a human being
A) Bronchi
B) Pharynx
C) Laryngopharynx
D) Trachea

Answer 1

Breathing involves two stages first, inspiration during which atmospheric air is drawn in and the second one is expiration by which the alveolar air is released out from the body.

Complete answer:
Breathing is the movement of air in and out of the lungs which is carried out by creating a pressure gradient between the lungs and the atmosphere.
A) Bronchi- The trachea at the fifth thoracic vertebra divides into left and right primary bronchi. Each terminal bronchi undergoes repeated division to form secondary and tertiary bronchi and bronchioles. Each terminal bronchioles gives rise to several very thin-walled, irregular walled, and vascularized bag-like structures called alveoli. It is the primary site for the exchange of gases.
B) Pharynx- The nasal chamber opens into the pharynx. It is a common passage for both food and air.
C) Laryngopharynx- Laryngopharynx is a part of the pharynx where both food and air passes. It is a connection point and guides food and water where to go.
D) Trachea (windpipe) - The pharynx opens to the larynx region into the trachea. It transmits the air from the nasal chamber to the alveoli or vice-versa.
Thus, option A is the correct answer.

Note: Exchange of gases also occurs between blood and tissue. Oxygen and carbon dioxide are exchanged in these sites by simple diffusion mainly based on pressure/concentration gradient of the gases as well as the thickness of the membrane is involved in diffusion are also some important factors that can affect the rate of diffusion.