Final answer:
The term for the portion of tidal volume that does not reach the alveoli is Dead Space. Dead space refers to the air within the respiratory structures that never reaches functional alveoli. It is important to consider dead space when assessing respiratory health and gas exchange.
Step-by-step explanation:
The term for the portion of tidal volume that does not reach the alveoli and therefore does not participate in gas exchange is Dead Space. Dead space refers to the air within the respiratory structures that never reaches functional alveoli. It includes both anatomical dead space in the airway and alveolar dead space in non-functioning alveoli. The dead space volume is important to consider when assessing respiratory health and gas exchange.