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Air enters the respiratory system through nostrils or external nares into nasal vestibule. From vestibule to internal nares: through superior, middle, and inferior meatuses. Constricted passageways that produce air turbulence that:
o warm and humidify incoming air
o trap particles
The Nasal Mucosa warm and humidify inhaled air for arrival at lower respir...

Air enters the respiratory system through nostrils or external nares into nasal vestibule. From vestibule to internal nares: through superior, middle, and inferior meatuses. Constricted passageways that produce air turbulence that:
o warm and humidify incoming air
o trap particles
The Nasal Mucosa warm and humidify inhaled air for arrival at lower respiratory organs. Breathing through mouth bypasses this important step.
The Pharynx, a chamber shared by digestive and respiratory systems, extends from internal nares to entrances to larynx and esophagus.
The Nasopharynx
* Superior portion of the pharynx
* Contains pharyngeal tonsils and openings to left and right auditory tubes
The Oropharynx
* Middle portion of the pharynx
* Communicates with oral cavity
The Laryngopharynx
* Inferior portion of the pharynx
* Extends from hyoid bone to entrance to larynx and esophagus
The Epiglottis Prevents entry of food and liquids into respiratory tract.
* Air passing through glottis:
o vibrates vocal folds
o produces sound waves
The Trachea
* Also called the windpipe
* Extends from the cricoid cartilage into mediastinum
o where it branches into right and left pulmonary bronchi
The Right Lung
* Has 3 lobes:
o superior, middle, and inferior
o separated by horizontal and oblique fissures
The Left Lung
* Has 2 lobes:
o superior and inferior
o are separated by an oblique fissure
* The walls of primary, secondary, and tertiary bronchi:
o contain progressively less cartilage and more smooth muscle
o increasing muscular effects on airway constriction and resistance
* Each terminal bronchiole delivers air to a single pulmonary lobule
* Each pulmonary lobule is supplied by pulmonary arteries and veins
1 tertiary bronchus forms about 6500 terminal bronchioles.
What physical principles govern the movement of air into the lungs?
Atmospheric Pressure
* The weight of air: has several important physiological effects
Boyle’s Law
* Defines the relationship between gas pressure and volume:
* As volume decreases, pressure increases
* In a contained gas:
o external pressure forces molecules closer together
o movement of gas molecules exerts pressure on container

* Diaphragm:
o contraction draws air into lungs
o 75% of normal air movement
* External intracostal muscles:
o assist inhalation
o 25% of normal air movement
* Accessory muscles assist in elevating ribs:
o sternocleidomastoid
o serratus anterior
o pectoralis minor
o scalene muscles