overloading the system with oxygen and depleting
the carbon dioxide needed for balance.
ANATOMY OF THE RESPIRATORY
Air enters the nasal chambers and the mouth,
then passes through the pharynx, larynx, and
bronchi into the bronchioles, which form a net-
work around the alveolar air sacs in the lungs
(figs. 3-34 and 3-35).
Air enters the NASAL CAVITY through the
nostrils (NARES). Lining the nasal passages are
hairs, which together with the mucous membrane,
entrap and filter out dust and other minute par-
ticles that could irritate the lungs. Incoming air
is warmed and moistened in the chambers of the
nasal cavity to prevent damage to the lungs.
The mouth and nose serve as auxiliary
The PHARYNX, or throat, serves both the
respiratory and digestive systems and aids in
speech. It has a mucous membrane lining that
traps microscopic particles in the air and aids in
adjusting temperature and humidifying inspired
air. The pharynx connects with the mouth and
nasal chambers posteriorly. According to its loca-
tion, it is referred to as:
NASOPHARYNXposterior to the nasal
OROPHARYNXposterior to the
Figure 3-35 .The lung and air passages
The EPIGLOTTIS is a lidlike, cartilaginous
structure that covers the entrance to the larynx
and separates it from the pharynx. It acts as a trap
door to deflect food particles and liquids from
the entrance to the larynx and trachea.
The LARYNX, or voice box, is a triangular
cartilaginous structure located between the tongue
and the trachea. It is protected anteriorly by the
thyroid cartilage (Adams apple), which is usu-
ally larger and more prominent in men than in
women. During the act of swallowing, it is pulled
upward and forward toward the base of the
tongue. The larynx is responsible for the produc-
tion of voice. This is accomplished by the passing
of air over the vocal cords. The ensuing vibra-
tions can be controlled to produce the sounds of
speech or singing. The nose, mouth, throat, bone
sinuses, and chest serve as resonating chambers
to further refine and individualize the voice.
The TRACHEA, or windpipe, begins at the
lower end of the larynx and terminates by dividing
into the right and left bronchi. It is a long tube
composed of 16 to 20 C-shaped cartilaginous
rings, embedded in a fibrous membrane, that sup-
port its walls, preventing their collapse (fig. 3-35).
The trachea has a ciliated mucous membrane
lining that entraps dust and foreign material. It
also propels secretions and exudates from the
lungs to the pharynx, where they can be
The BRONCHI are the terminal branches of
the trachea, which carry air to each lung and fur-
ther divide into the bronchioles (fig. 3-35).
The BRONCHIOLES are much smaller than
the bronchi and lack supporting rings of cartilage.
They terminate at the alveoli (fig. 3-36).
The ALVEOLI are thin, microscopic air sacs
within the lungs. They are in direct contact with
the pulmonary capillaries. It is here that fresh ox-
ygen exchanges with carbon dioxide by means of
Figure 3-36.Bronchiole and alveoli.