Key Terms
Conducting Zone
Everything that moves air but does NOT exchange gases.
Respiratory Zone
Structures that DIRECTLY participate in gas exchange.
Conchae
Three bony projections on each lateral wall (superior, middle, inferior). They increase surface area and disrupt airflow
Paranasal sinuses
Four paired cavities in skull bones (frontal, maxillary, sphenoidal, ethmoidal). Warm and humidify air, produce mucus, r
Lining
Pseudostratified ciliated columnar epithelium with goblet cells. Goblet cells produce mucus to trap debris.
Nasopharynx
Air only. Contains pharyngeal tonsils (adenoids) and the openings to the auditory (Eustachian) tubes.
Oropharynx
Air AND food. Contains palatine and lingual tonsils.
Laryngopharynx
Inferior; air goes anterior into larynx, food goes posterior into esophagus.
Thyroid cartilage
Largest; forms the laryngeal prominence (Adam's apple) Cricoid cartilage: ring-shaped; inferior to thyroid Epiglottis: e
True vocal cords
White membranous folds; free inner edges oscillate to produce sound. Larger folds produce lower-pitched voices.
Branching sequence
Primary bronchi -> Secondary (lobar) bronchi -> Tertiary (segmental) bronchi -> Bronchioles -> Terminal bronchioles
Alveolar duct
Smooth muscle tube opening into a cluster of alveoli
Alveolar sac
A cluster of individual alveoli Alveolus: single grape- like sac; approximately 200 micrometers in diameter; walls are e
Type I alveolar cells
Squamous epithelial cells; cover 97% of the alveolar surface; extremely thin (about 25 nm); highly permeable to gases. P
Type II alveolar cells
Cuboidal cells; secrete pulmonary surfactant (phospholipids + proteins). Surfactant reduces surface tension so alveoli d