The nasal cavity belongs to the upper respiratory tract due to its role in inspiration and exhalation. Belonging to the posterior nasal cavity is the nasopharynx, the first part of the pharynx. The nasopharynx is continuous caudally with the oropharynx (throat), the posterior part of the oral cavity leading to the larynx and esophagus. The nasopharynx lining’s mucosa contains the medial pharyngeal tonsil and the opening of the two auditory tubes which connect to each middle ear cavity.

The lower respiratory tract houses the lungs where gas exchange actually occurs. The lung is a respiratory organ through which air moves by a ventilating mechanism comprising the thoracic cage, intercostal muscles, diaphragm, and elastic components of the lung tissue. The alveoli are where O2 and CO2 exchanges occur with blood in the surrounding capillaries of the lungs.

REFERENCES:
Belleza, M. (2021, February 11). Respiratory System Anatomy and Physiology. Nurseslabs. https://nurseslabs.com/respiratory-system/
Mescher, A. (2018). Junqueira’s basic histology: text and atlas (15th ed.). Mcgraw Hill Education.