Arrange the following parts of the human respiratory tract in the same order in which air flows during expiration:
Nasal chamber, pharynx, larynx, internal nares, trachea, lungs
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Solution
The correct option is D Lungs -> trachea -> larynx -> pharynx -> internal nares -> nasal chamber Expiration is the process by which the alveolar air (after gaseous exchange) is released from the lungs into the atmosphere via the respiratory tract. From the body surface, the respiratory tract starts with the external nostrils which open into vestibules and then continue up to the pharynx via nasal chambers, internal nares, and nasopharynx respectively. The pharynx is the common passage for food and air, which opens into the larynx in the respiratory tract via the glottis. The larynx in turn opens into the trachea which further joins both the lungs via bronchi.
In the case of inspiration, the air from the atmosphere passes via these parts in order to reach the lungs. The pathway in case of inspiration is shown below:
But in expiration, the pathway is just the opposite in which the alveolar air from the lungs goes into the pharynx via trachea and larynx sequentially. From the pharynx, it goes to internal nares, and then via the nasal chamber and nostrils, it is released outside to the atmosphere. Hence, the correct sequence is:
Lungs -> trachea -> larynx -> pharynx -> internal nares -> nasal chamber