The Airways and Alveoli

Vocabulary flashcards covering key terms and definitions from the lecture notes on the Airways and Alveoli.

Upper airway

The nose, nasal cavity, pharynx, and larynx; responsible for warming, humidifying, and filtering inspired air before it reaches the lower airways.

Lower airway

Structures below the larynx (trachea, bronchi, bronchioles) that conduct air to the gas-exchange membranes; gas exchange does not occur until the alveoli.

Conducting airways

Airway passages that provide a route for air to reach the gas-exchange membranes; no gas exchange occurs here.

Respiratory zone

Lung regions where gas exchange occurs: respiratory bronchioles, alveolar ducts, and alveoli.

Mucociliary clearance

The coordinated movement of mucus by cilia to remove inhaled particles and pathogens toward the pharynx.

Mucus blanket

The two-layer mucus system covering the airway epithelium: a gel layer and a more watery sol layer.

Gel layer

The sticky, viscid layer of the mucus blanket that traps particles.

Sol layer

The watery, less viscous layer beneath the gel layer that enables ciliary movement.

Cilia

Hair-like projections on airway epithelial cells that beat rapidly (about 1300 times per minute) to move mucus toward the pharynx.

Goblet cell

Mucus-secreting cells within the airway epithelium.

Pseudostratified ciliated columnar epithelium

The typical epithelium lining the conducting airways, containing goblet cells and cilia.

Lamina propria

Connective tissue beneath the epithelium containing smooth muscle, elastic fibers, and blood vessels.

Submucosa

Layer containing submucosal glands that produce mucus in the airways.

Adventitia

Outer connective tissue cover surrounding cartilaginous airways and blood vessels.

Nasal turbinates

Bony projections (superior, middle, inferior) that increase surface area for warming, humidifying, and filtering air.

Nares

Nostrils; the external openings of the nasal cavity.

Vibrissae

Nasal hairs that help filter large particles from inspired air.

Nasal septum

The cartilage and bone structure dividing the two nasal passages.

Nasal fossae

The nasal cavity recesses bounded by bone and cartilage through which air passes.

Choanae

Internal nasal openings that connect the nasal cavity to the nasopharynx.

Epiglottis

Leaf-shaped cartilage that covers the glottis during swallowing to protect the airway.

Vallecula

The space between the epiglottis and the tongue; an important landmark during intubation.

Larynx

The voice box; a cartilaginous structure containing the vocal cords and separating the upper and lower airways.

Thyroid cartilage

Main cartilage of the larynx; also known as the Adam’s apple.

Cricoid cartilage

Ring-shaped cartilage below the thyroid cartilage forming part of the laryngeal skeleton.

Vocal cords (true vocal cords)

Tissue folds within the larynx that vibrate to produce sound.

Vestibular folds (false vocal cords)

Mucosal folds superior to the true vocal cords that do not vibrate to produce sound.

Rima glottidis

The opening between the true vocal cords; the narrowest part of the adult upper airway.

Glottis

The opening and surrounding structures formed by the vocal cords and laryngeal inlet.

Carina

The bifurcation point where the trachea divides into the right and left main bronchi.

Right main bronchus

The shorter, wider, and more vertical main bronchus that branches from the trachea.

Left main bronchus

The longer, narrower, and more horizontal main bronchus that branches from the trachea.

Main bronchi

The two primary branches of the trachea that enter each lung and divide into lobar bronchi.

Bronchus (bronchi)

Airways that conduct air from the trachea to the bronchioles; presence of cartilage in larger airways diminishes distension with each breath.

Bronchioles

Smaller airways lacking cartilage; contain smooth muscle and can constrict (bronchoconstriction).

Terminal bronchioles

End of the conducting airways; lack cartilage and contain smooth muscle; can nearly close during constriction.

Alveolus

The tiny air sacs where gas exchange occurs; collectively form the gas-exchange surface of the lung.

Type I alveolar cell

Thin alveolar cell covering most of the alveolar surface, facilitating gas exchange.

Type II alveolar cell

Alveolar cells that secrete surfactant and contain lamellar bodies.

Surfactant

Lipid-protein substance reducing surface tension in alveoli to prevent collapse and aid expansion.

Alveolar macrophage

Immune cell within alveolar spaces that phagocytose debris and pathogens.

Pores of Kohn

Small alveolar connections that allow collateral ventilation between adjacent alveoli.

Canals of Lambert

Channels linking terminal bronchioles to nearby alveoli, aiding collateral ventilation.

Alveolar-capillary membrane

Thin barrier (<0.5 μm) between alveolar air and capillary blood; essential for gas exchange.

Isothermic saturation boundary (ISB)

Point in the airways where inspired gas is at body temperature and fully saturated with water vapor (37°C, 100% RH).

Endotracheal intubation (ETT) and dead space

Insertion of an endotracheal tube that increases the volume of anatomical dead space, impacting ventilation efficiency.

Mucociliary clearance impairment factors

Conditions like cigarette smoke, air pollution, and dehydration that reduce ciliary function or mucus transport.

Mucus layers impairment in disease

Excess mucus production and altered mucus properties in CB, CF, and asthma can hinder clearance.

Airway obstruction and aspiration reflexes

Pharyngeal musculature and reflexes (gag/swallow) prevent aspiration; glossopharyngeal IX and vagus X nerves mediate these reflexes.

Pharynx divisions

Nasopharynx (behind nasal cavity), oropharynx (behind oral cavity), and laryngopharynx (below base of tongue, above larynx).

Obstructive Sleep Apnea (OSA)

Sleep disorder where pharyngeal soft tissues obstruct the airway; CPAP therapy helps keep the airway open.

CPAP

Continuous positive airway pressure therapy used to treat OSA by splinting the airway open during sleep.