Anatomy & Physiology
Chapter 26: Anatomy of the Respiratory
System
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Structural Plan of the
Respiratory System

Structure determined by respiratory system
functions of air distributor and gas exchanger—
supplying oxygen and removing carbon dioxide
from cells (Figure 26-1)
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Alveoli—sacs that serve as gas exchangers;
all other parts of respiratory system serve
as air distributors
The respiratory system also warms, filters,
and humidifies air
Respiratory organs involved in speech,
homeostasis of body pH, and olfaction
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Structural Plan of the
Respiratory System

The respiratory system is divided into two
structural divisions
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Upper respiratory tract—the organs are
located outside the thorax and consist of the
nose, nasopharynx, oropharynx,
laryngopharynx, and larynx
Lower respiratory tract—the organs are
located within the thorax and consist of the
trachea, the bronchial tree, and the lungs
Accessory structures include the oral cavity,
rib cage, and diaphragm
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Upper Respiratory Tract
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Nose
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Structure of the nose—external portion
consists of a bony and cartilaginous
frame covered by skin containing
sebaceous glands
 The two nasal bones meet and are
surrounded by the frontal bone to
form the root
 The nose is surrounded by the
maxilla (Figure 26-2)
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Upper Respiratory Tract

Nose (cont)
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Internal portion of the nose (nasal cavity) lies over the roof of
the mouth, separated by the palatine bones
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Cleft palate—condition in which the palatine bones fail to
unite completely and only partially separate the nose and
the mouth, thereby producing difficulty swallowing
Cribriform plate—separates the roof of the nose from the
cranial cavity
Septum—separates the nasal cavity into right and left
cavities; it consists of four structures: the perpendicular
plate of the ethmoid bone, the vomer bone, the
vomeronasal cartilages, and the septal nasal cartilage
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Upper Respiratory Tract

Nose (cont)
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Each nasal cavity is divided into three
passageways: superior, middle, and
inferior meatuses (Figure 26-3)
Anterior (external) nares—external
openings to the nasal cavities; open into
the vestibule
Sequence of airflow through the nose into
the pharynx—anterior nares to the
vestibule to all three meatuses
simultaneously and then to the posterior
(internal) nares
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Upper Respiratory Tract

Nose (cont)
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Nasal mucosa
 Air passes over respiratory
mucosa, which contains a rich
blood supply (Figure 26-4)
 Olfactory epithelium—special
sensory membrane containing
many olfactory nerve cells and a
rich lymphatic plexus
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Upper Respiratory Tract

Nose (cont)

Paranasal sinuses
 Four pairs of air-containing
spaces that open or drain into the
nasal cavity
 Each is lined with respiratory
mucosa (Figure 26-5)
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Upper Respiratory Tract
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Nose (cont)
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Functions of the nose
 Provides a passageway for air
traveling to and from the lungs
 Filters the air, aids speech, and
makes possible the sense of smell
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Upper Respiratory Tract

Pharynx (throat)
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Structure of pharynx
 Tubelike structure extending from
the base of the skull to the
esophagus
 Made of muscle and divided into
three parts (Figure 26-3)—
nasopharynx, oropharynx, and
laryngopharynx
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Upper Respiratory Tract
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Pharynx (cont)
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Pharyngeal tonsils
• Located in the nasopharynx
• Called adenoids when they become
enlarged
Oropharynx contains two pair of organs—the
palatine tonsils (most commonly removed in
tonsillectomy) and the lingual tonsils (rarely
removed)
Functions of the pharynx—pathway for the
respiratory and digestive tracts
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Upper Respiratory Tract

Larynx (Figures 26-6 and 26-7)
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Location of larynx—positioned between
the root of the tongue and the upper end of
the trachea
Structure of larynx
• Consists of cartilages attached to each
other by muscle
• Lined by a ciliated mucous membrane,
which forms two pairs of folds (Figure
26-8)— vestibular folds (false vocal
folds) and vocal folds
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Upper Respiratory Tract
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Larynx (cont)
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Cartilages (framework) of the larynx—
formed by nine cartilages
• Single laryngeal cartilages—the three
largest cartilages: the thyroid
cartilage, the epiglottis, and the cricoid
cartilages
• Paired laryngeal cartilages—three
pairs of smaller cartilages: the
arytenoid, the corniculate, and the
cuneiform cartilages
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Upper Respiratory Tract

Larynx (cont)
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Muscles of the larynx
 Intrinsic muscles both insert and
originate within the larynx
 Extrinsic muscles insert in the
larynx but originate on some other
structure
Functions of the larynx—forms part of
the airway to the lungs and produces
the voice
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Lower Respiratory Tract

Trachea—often called “windpipe” (Figure 26-10)

Structure of trachea
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Extends from the larynx to the primary bronchi
Wall composed of (outer) adventitia, (middle)
smooth muscle and C-shaped cartilage rings,
(inner) respiratory mucosa; posterior wall is very
elastic (Figure 26-11)
Incomplete rings and posterior elasticity allows
esophagus to expand into trachea during
swallowing
Functions of trachea—furnishes part of the
open airway to the lungs; obstruction causes
death
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Lower Respiratory Tract

Bronchi and alveoli
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Structure of bronchi
 Lower end of the trachea divides into
two primary bronchi, one on the right
and one on the left
 Primary bronchi enter the lung and
divide into secondary bronchi, which
branch into bronchioles and eventually
divide into alveolar ducts and alveoli
 23 levels of branching (Figure 26-12)
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Lower Respiratory Tract
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Bronchi and alveoli (cont)
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Structure of alveoli—the primary gas
exchange structures
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Respiratory membrane—the barrier between
which gases are exchanged by alveolar air
and blood (Figure 26-15)
Respiratory membrane consists of the alveolar
epithelium, the capillary endothelium, and their
joined basement membranes
Surfactant—a component of the fluid coating
the respiratory membrane that reduces
surface tension; produced by type II cells
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Lower Respiratory Tract

Bronchi and alveoli (cont)
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Functions of bronchi and alveoli
 Distribute air to the lung’s interior;
23 levels of branching are optimal
for oxygen transfer to the blood
 Mucus blanket cleans the airways
as it is moved upward by the ciliary
escalator
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Lower Respiratory Tract

Lungs
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Structure of the lungs—cone-shaped
organs extending from the diaphragm to
above the clavicles (Figure 26-17)
 Hilum—slit on the lung’s medial
surface where the primary bronchi
and pulmonary blood vessels enter
 Base—the inferior surface of the lung
that rests on the diaphragm
 Costal surface—lies against the ribs
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Lower Respiratory Tract
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Structure of the lungs (cont)
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Left lung is divided into two lobes—superior and
inferior
Right lung is divided into three lobes—superior,
middle, and inferior
Lobes are further divided into functional units—
bronchopulmonary segments
 Ten segments in the right lung
 Eight segments in the left lung
Functions of the lungs—air distribution and
gas exchange
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Lower Respiratory Tract
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Thorax (Figure 26-18)
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Structure of the thoracic cavity—three
divisions divided by the pleura
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Pleural divisions—the part occupied by the
lungs
Mediastinum—part occupied by the
esophagus, trachea, large blood vessels,
and heart
Functions of the thorax—brings about
inspiration and expiration
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Cycle of Life: Respiratory System
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Respiration may be affected by
developmental defects, age-related
structural changes, or loss of function
throughout the life cycle
Age-related changes affect lung capacity,
make ventilation difficult, or reduce the
oxygen- or carbon dioxide–carrying
capacity of blood
Respiratory efficiency is reduced in old age
as a result of changes in ribs, respiratory
muscles, and hemoglobin levels
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