742
UNIT FIVE
the gaps between their ends are f
lled with smooth muscle
and connective tissues
(f
gs. 19.9
and
19.10)
. These cartilag-
inous rings prevent the trachea From collapsing and blocking
the airway. At the same time, the soFt tissues that complete
the rings in the back allow the nearby esophagus to expand
as Food moves through it on the way to the stomach.
A blocked trachea can cause asphyxiation in minutes. IF
swollen tissues, excess secretions, or a Foreign object obstruct
the trachea, making a temporary, external opening in the tube
so that air can bypass the obstruction is liFesaving. This proce-
dure, shown in
f gure 19.11
, is called a
tracheostomy.
On December 13, 1799, George Washington spent the day walking
on his estate in a freezing rain. The next day, he had trouble breath-
ing and swallowing. Several doctors were called in. One suggested
a tracheostomy, cutting a hole in the throat so that the president
could breathe. He was voted down. The other physicians suggested
bleeding the patient, plastering his throat with bran and honey, and
placing beetles on his legs to produce blisters. No treatment was pro-
vided, and within a few hours, Washington’s voice became muF
ed,
breathing was more labored, and he was restless. ±or a short time he
seemed euphoric, and then he died.
George Washington had
epiglottitis,
an in²
ammation that swells
the epiglottis to ten times its normal size. A tracheostomy might have
saved his life.
Trachea
The
trachea
(windpipe) is a fl
exible cylindrical tube about
2.5 centimeters in diameter and 12.5 centimeters in length.
It extends downward anterior to the esophagus and into the
thoracic cavity, where it splits into right and leFt bronchi
(
f
g. 19.8
and reFerence plate 9).
The inner wall oF the trachea is lined with a ciliated
mucous membrane that has many goblet cells. This mem-
brane continues to Filter the incoming air and to move
entrapped particles upward into the pharynx where the
mucus can be swallowed.
Within the tracheal wall are about twenty C-shaped
pieces oF hyaline cartilage, one above the other. The open
ends oF these incomplete rings are directed posteriorly, and
FIGURE 19.8
The trachea transports air between the larynx and the bronchi.
Posterior portion
of tongue
Inner lining
of trachea
Glottis
Corniculate cartilage
(a)
(b)
Epiglottis
Glottis
True vocal
cord
Cuneiform
cartilage
False vocal
cord
(c)
Larynx
Trachea
Thyroid
cartilage
Cricoid
cartilage
Cartilaginous
ring
Carina
Superior (upper)
lobe bronchus
Superior (upper)
lobe bronchus
Right primary
bronchus
Left
primary
bronchus
Middle lobe
bronchus
Inferior (lower)
lobe bronchi
FIGURE 19.7
The vocal cords as viewed from above with
the glottis (
a
) closed and (
b
) open. (
c
) Photograph of the
glottis and vocal cords.
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