CHAPTER 11
Respiratory System
219
Tract
Epithelium
Glands
Skeletal
Support
Muscle
Special Features and Main
Functions
Upper Airway
Conducting portion
Nasal cavity
Nasal
vestibule
Stratif ed squamous
epithelium
Sebaceous and sweat
glands
Hyaline
cartilage
None
Vibrissae present; block large
particles and small insects
Nasal mucosa
Respiratory
epithelium
Mixed mucoserous
glands
Bone and hya-
line cartilage
None
Venous plexuses warm air to
body temperature
OlFactory
mucosa
Specialized olFactory
epithelium
Serous (Bowman)
glands
Bone
None
OlFactory receptor neurons in
epithelium detect smell and
odorants
Nasopharynx
and orophar-
ynx
Respiratory and
Stratif ed squamous
epithelium
Seromucous (mixed)
glands
Bone
Skeletal
muscle
Pharyngeal and
palatine
tonsils;
f rst-line
immunological deFense
Larynx
Epiglottis and
Vocal cords
Stratif ed squamous and
respiratory
epithelium
Mostly mucous
glands and some
serous or mixed
glands
Hyaline and
elastic carti-
lage
Skeletal
(vocalis)
muscle
Vocal cords control airfl ow and
speaking; epiglottis prevents Food
and fl uid From entering trachea
Lower Airway
Trachea
Respiratory
epithelium
Mostly mucous
glands and some
serous or mixed
glands
C-shaped hya-
line
cartilage
rings
Smooth
(trachealis)
muscle
Trachealis muscle bridges open-
ing ends oF cartilage
Extrapulmonary
(primary) bronchi
Respiratory
epithelium
Mucous and serous
(mixed glands)
C-shaped
hyaline
cartilage
rings
Smooth
muscle
Two primary bronchi outside
each lung biFurcate From trachea;
C-shaped cartilage
Intrapulmonary
bronchi
Respiratory
epithelium
Mucous and serous
(mixed glands)
Large and
small plates oF
hyaline carti-
lage
Prominent
spiral band
oF smooth
muscle
Secondary and tertiary
bronchi
branch repeatedly; spiral smooth
muscle band lies between lamina
propria and submucosa
Bronchioles
Simple ciliated
columnar
to cuboidal; Clara cells
present
Occasional goblet
cells in large bron-
chioles, but not in
small bronchioles
No cartilage
Smooth
muscle
Clara cells are present
Terminal
bronchioles
Simple ciliated
cuboidal;
numerous Clara cells
No goblet cells in
normal cases
None
Some
smooth
muscle
Numerous Clara cells are pres-
ent in these smallest conducting
airways
Respiratory portion
Respiratory
bronchioles
Simple cuboidal cells
with Few cilia; a Few
Clara cells; some type I
and II pneumocytes
No goblet cells
None
±ew smooth
muscle cells
Alveoli interrupt simple cuboidal
epithelium; gas exchange begins
here
Alveolar ducts/
alveolar sacs
Rarif ed simple
cuboidal
epithelium between
alveoli; no Clara cells
No goblet cells
None
±ew smooth
muscle cells
Air passes into alveoli For gas
exchange
Alveoli
Type I and II
pneumocytes
No goblet cells
None
None
Blood-air barrier is the
primary
site For gas exchange
TABLE 11-1
Respiratory System
SYNOPSIS 11-2
Structural Differences (From Upper to Lower Airway) in the Respiratory System
Epithelium
changes From keratinized to nonkeratinized stratif
ed squamous and then to respiratory epithelium.
Respiratory epithelium
changes From simple columnar to cuboidal and then to simple squamous (alveolar cells).
Glands
gradually decrease in numbers and disappear in bronchioles as airways become smaller.
Skeletal support
changes From bone to cartilage to none at all.
Cartilage
changes From C-shaped rings to large irregular plates to small plates and disappears in bronchioles and levels below.
Muscle
changes From skeletal to smooth muscle; numbers oF smooth muscle cells decrease.
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