ide into the air. Without ventilation (breathing), however,
the respiration process would soon be out of commission.
The Respiratory Organs Are
Functionally Divided into Upper
and Lower Respiratory Tracts
The upper respiratory tract consists of the nose, nasal
epithelium, and pharynx; it warms, filters, and humidi-
fies incoming air; detects smells in that air; and expels
mucus from the respiratory tract. The lower respiratory
tract starts with the larynx, which serves as the entrance
into the trachea. The epiglottis, a portion of the larynx,
covers the glottis, the vocal folds in the layrnx plus the
space between them, during swallowing so that food does
not enter the airways. The larynx is also involved in pro-
ducing sounds. Within the larynx are several folds of tis-
sues, the vocal cords, which aid in the creation of sound.
As air passes through the larynx, the vocal cords vibrate,
changing the flow of air through the passage.
The lower respiratory tract continues with the trachea,
bronchi, bronchioles, and lungs. The trachea, bronchi,
and bronchioles are a series of branching tubes that directs
the air into and through the lung tissue. Because all of the
airways resemble an upside-down tree with many branches,
their arrangement is known as the bronchial tree.
b. Lower respiratory
or voice box, is a short tube of
cartilage that connects the pharynx
with the trachea. The larynx contains
the vocal cords, which produce sounds.
is a leaf-like flap
of cartilage that covers the
airway during swallowing.
Thyroid cartilage
(Adams’s apple)
arytenoid cartilage
are attachment points for
the vocal cords.
Anterior view
Posterior view
Superior lobe of lung
(right and left).
Horizontal fissure
separates superior and
middle lobes of lung
(right only).
Oblique fissure
middle and inferior lobes of
lung (right and left).
Inferior lobe of lung
(right and left).
—Cartilaginous tube that extends
from larynx to bronchi (at vertebra T5). It
is the main airway and is lined with a
mucous membranes that move trapped
particles upward to the pharynx.
Pleural membranes
enclose and protect
each lung.
Pleural cavity
— Fluid-filled
space between lungs and
pleural membranes that
connects the lungs to the
thoracic wall.
right bronchi
connect trachea with left and right lungs;
pulmonary blood vessels, lymph vessels, and
nerves enter and exit along bronchial passages.
branch from primary bronchi.
are smaller tubes that
branch from tertiary bronchi.
— Indentation in left
lung where heart sits.
Middle lobe of lung
(right only)
—One of the
major respiratory muscles.
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