Chapter 25
*Lecture Outline
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Chapter 25 Outline
• General Organization and Functions of the Respiratory
System
• Upper Respiratory Tract
• Lower Respiratory Tract
• Lungs
• Pulmonary Ventilation
• Thoracic Wall Dimensional Changes During External
Respiration
• Innervation of the Respiratory System
• Aging and the Respiratory System
• Development of the Respiratory System
Figure 25.1
Respiratory System Functions
•
•
•
•
•
The main function of the respiratory
system is breathing. This involves both
inhalation and exhalation. Some of the
other functions are:
Gas conditioning
Sound production
Olfaction
Defense
Division of the
Respiratory System
• Anatomically, the system can be divided
into upper and lower respiratory tracts.
• Functionally, the system can be divided
into conducting and respiratory
portions.
Upper Respiratory Tract
The upper respiratory tract is comprised of
the following:
• nose and nasal cavities
• paranasal sinuses
• pharynx
These are all part of the conducting portion
of the respiratory system.
Upper Respiratory System
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Paranasal
sinuses
Nasal
cavity
Frontal sinus
Sphenoidal sinus
Superior nasal concha
Middle nasal concha
Inferior nasal concha
Vestibule
Nostril
Hard palate
Oral cavity
Tongue
Superior meatus
Middle meatus
Nasal
Inferior meatus
cavity
Choanae
Pharyngeal tonsil
Opening of auditory tube
Soft palate
Uvula
Nasopharynx
Oropharynx
Laryngopharynx
Palatine tonsil
Lingual tonsil
Epiglottis
Larynx
Thyroid cartilage
Cricoid cartilage
Figure 25.2
Esophagus
Trachea
Pharynx
Nose
• The nose is the main conducting airway
for inhaled air.
• It is supported by paired nasal bones
superiorly that form the bridge of the nose.
• It is supported anteroinferiorly from the
bridge by the fleshy, cartilaginous dorsum
nasi.
Nasal Cavity
• The nasal cavity begins as the internal
component of the nose and ends as openings to
the nasopharynx known as choanae.
• The nasal septum divides the nasal cavity into
right and left portions and forms the medial wall
of each cavity.
• The superior, middle and inferior nasal
conchae form the lateral wall for each cavity.
• The conchae condition the air within the nasal
cavity.
Paranasal Sinuses
Four bones of the skull contain paired air
spaces called paranasal sinuses. These
spaces make the bones lighter in weight and
are named after the bones in which they
reside:
• frontal
• ethmoidal
• sphenoidal
• maxillary
Paranasal Sinuses
Figure 25.3
Pharynx
One of the few areas of the body that is
shared by two organ systems (digestive and
respiratory). The pharynx is divided into
three regions:
• nasopharynx
• oropharynx
• laryngopharynx
Nasopharynx
• Continuous with the nasal cavity and
superior to the soft palate
• Opening of the auditory tubes found in
the lateral walls
• Posterior nasopharynx wall houses a
single pharyngeal tonsil (adenoids)
Upper Respiratory System
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Paranasal
sinuses
Nasal
cavity
Frontal sinus
Sphenoidal sinus
Superior nasal concha
Middle nasal concha
Inferior nasal concha
Vestibule
Nostril
Hard palate
Oral cavity
Tongue
Superior meatus
Middle meatus
Nasal
Inferior meatus
cavity
Choanae
Pharyngeal tonsil
Opening of auditory tube
Soft palate
Uvula
Nasopharynx
Oropharynx
Laryngopharynx
Palatine tonsil
Lingual tonsil
Epiglottis
Larynx
Thyroid cartilage
Cricoid cartilage
Figure 25.2
Esophagus
Trachea
Pharynx
Oropharynx
• Begins at the end of the soft palate and ends at
the level of the hyoid bone
• The opening of the oral cavity into the
oropharynx is the fauces, defined by two pair of
muscular arches on the lateral walls of the
fauces
• The palatine tonsils are embedded in the
lateral wall between the arches
• The lingual tonsils are at the base of the
tongue
Laryngopharynx
• Starts inferior to hyoid bone and is
continuous with the larynx and esophagus
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Paranasal
sinuses
Nasal
cavity
Frontal sinus
Sphenoidal sinus
Superior nasal concha
Middle nasal concha
Inferior nasal concha
Vestibule
Nostril
Hard palate
Oral cavity
Tongue
Superior meatus
Middle meatus
Nasal
Inferior meatus
cavity
Choanae
Pharyngeal tonsil
Opening of auditory tube
Soft palate
Uvula
Nasopharynx
Oropharynx
Laryngopharynx
Palatine tonsil
Lingual tonsil
Epiglottis
Larynx
Figure 25.2
Thyroid cartilage
Cricoid cartilage
Esophagus
Trachea
Pharynx
Regions of the Pharynx
Regions of the Pharynx
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Frontal sinus
Paranasal
sinuses
Sphenoidal sinus
Superior meatus
Superior nasal concha
Middle meatus
Middle nasal concha
Nasal
cavity
Nasal
cavity
Inferior meatus
Inferior nasal concha
Choanae
Vestibule
Pharyngeal tonsil
Nostril
Hard palate
Opening of auditory tube
Oral cavity
Nasopharynx
Oropharynx
Soft palate
Uvula
Tongue
Pharynx
Laryngopharynx
Palatine tonsil
Lingual tonsil
Epiglottis
Larynx
Esophagus
Thyroid cartilage
Trachea
Cricoid cartilage
Pharynx:
Nasopharynx
Oropharynx
Laryngopharynx
Ethmoidal sinuses
Sphenoidal sinus
Superior nasal concha
Superior meatus
Middle nasal concha
(b) Regions of pharynx
Middle meatus
Inferior nasal concha
Inferior meatus
Vestibule
Nasopharynx
Hard palate
Soft palate
Uvula
Tongue
Oral cavity
Oropharynx
Dentures
Lingual tonsil
Laryngopharynx
Epiglottis
Thyroid cartilage
Esophagus
Cricoid cartilage
Figure 25.2
(a) Sagittal section
a: © The McGraw- Hill Companies, Inc./Photo and Dissection by Christine Eckel
Lower Respiratory Tract
(Conducting Portion)
The lower respiratory tract is comprised of
the following :
• larynx
• trachea
• bronchi
• bronchioles
Lower Respiratory Tract
(Respiratory Portion)
The lower respiratory tract is comprised of
the following :
• respiratory bronchioles
• alveolar ducts
• alveoli
Lower Respiratory Tract
Larynx
•
•
•
•
Connects pharynx to trachea
Also called the voice box
Supported by a framework of cartilages,
ligaments, and muscles
The three major cartilages are:
1. Thyroid cartilage
2. Cricoid cartilage
3. Epiglottis
Major Cartilages of the Larynx
Figure 25.4
Thyroid Cartilage
•
•
•
•
Largest cartilage
Has an anterior and lateral wall
No posterior wall
V-shaped anterior projection is called the
laryngeal prominence (Adam’s apple)
• Usually larger in males than in females
because of testosterone influence on
growth of cartilage
Cricoid Cartilage
• Just inferior to the thyroid cartilage
• Complete ring-shaped cartilage
Figure 25.4
Epiglottis
• Spoon-shaped cartilage that projects
superiorly into pharynx
• Swallowing causes the epiglottis to close
the opening to the larynx thus preventing
materials from entering the lower
respiratory tract
Minor Cartilages of the Larynx
Although smaller than the three major
cartilages, these paired cartilages play an
important role in sound production. They
are:
• arytenoid cartilages
• corniculate cartilages
• cuneiform cartilages
Minor Cartilages of the Larynx
Figure 25.5
Sound Production
• Vocal folds are found in the larynx and are
comprised of vocal ligaments covered by a
mucous membrane.
• The opening between the vocal folds is the rima
glottidis.
• The vocal folds plus the rima glottidis are
collectively known as the glottis.
• When air is forced through the rima glottidis, it
causes vibration of the vocal folds, which results
in the production of sound.
Minor Cartilages of the Larynx
Figure 25.5
Trachea
• Inferior to the larynx, superior to the
primary bronchi, and anterior to the
esophagus
• 2.5 cm in diameter and 12–14 cm in length
• Supported by C-shaped tracheal
cartilages
Trachea
Figure 25.5
Trachea
• Posteriorly, the ends of the tracheal
cartilages are connected by the trachealis
muscle.
• The mucosa is lined with pseudostratified
columnar epithelium and mucin-secreting
goblet cells.
Trachea
Figure 25.7
Bronchiole Tree
• The bronchial tree is a highly branched
system of air-conducting passages that
begin with the primary bronchi and end
with the terminal bronchi.
• These passages belong to the conducting
portion of the respiratory system.
• They reside within the substance of the
lungs.
Bronchial Tree
Figure 25.8
Bronchial Tree
• The trachea branches into left and right primary
bronchi.
• The right primary bronchus is wider and more
vertical and foreign particles are more likely to
get lodged in this bronchus.
• The right primary bronchus divides into three
secondary bronchi.
• The left primary bronchus divides into two
secondary bronchi.
• The secondary bronchi divide into 8–10 tertiary
bronchi (segmental bronchi).
Bronchial Tree
As branching continues and the bronchioles
become smaller, the following is observed:
• Incomplete rings of cartilage become
smaller
and less numerous
• All bronchi are lined with pseudostratified
columnar epithelium
• Bronchi branch into bronchioles, which
lack rings
of cartilage and are lined not with
pseudostratified columnar epithelium, but
simple
columnar or simple squamous epithelium
Bronchioles
• Bronchioles are less than 1 mm in diameter.
• Their walls are composed of a relatively thick layer
of smooth muscle.
• Contraction of the smooth muscle results in a
narrowing of the bronchioles called
bronchoconstriction.
• Relaxation of the smooth muscle results in a
widening of the bronchioles called bronchodilation.
• Bronchioles branch into terminal bronchioles,
which are the last portions of the conduction portion
of the respiratory system.
Respiratory Portion of the
Respiratory System
The respiratory portion of the respiratory
system consists of:
• respiratory bronchioles
• alveolar ducts
• pulmonary alveoli
Bronchioles and Alveoli
Figure 25.9
Respiratory Portion of the
Respiratory System
• Terminal bronchioles branch into respiratory
bronchioles.
• Respiratory bronchioles branch into alveolar
ducts.
• Alveolar ducts end with small saccular
outpocketings called alveoli.
• The thin wall of the alveolus is the structure
where respiratory gases (oxygen and carbon
dioxide) diffuse between the blood and the air in
the lungs.
Bronchioles and Alveoli
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Branch of
pulmonary artery
Bronchiole
Terminal bronchiole
Respiratory bronchiole
Branch of
pulmonary vein
Arteriole
Capillary
beds
Alveolar duct
Alveoli
Connective
tissue
(a)
Terminal bronchiole
Respiratory
bronchiole
Alveolar
sac
Alveolar ducts
Alveoli
Alveolar duct
Alveoli
Respiratory bronchiole
Figure 25.9
LM 60x
(b)
SEM 180x
(c)
b: © The McGraw-Hill Companies, Inc./Photo by Dr. Alvin Telser; c: © Dr. David Phillips/Visuals Unlimited
Alveolus
The alveolar wall is formed from two types of
cells:
1. Alveolar type I cells—simple squamous
epithelial cells promote rapid diffusion of
gases
2. Alveolar type II cells—almost cuboidal
in shape and produce pulmonary
surfactant, which decreases surface
tension within the alveolus and prevents
the collapse of alveoli
Alveolus
Figure 25.10
Respiratory Membrane
It is the diffusion barrier across which
respiratory gases are exchanged between
the blood and the air in the alveoli. It
consists of the following:
• plasma membrane of the type I alveolar
cell
• plasma membrane of the capillary cell
• fused basement membrane of both cells
Respiratory Membrane
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Alveolar
Nucleus of capillary
connective Nucleus
endothelial cell
tissue
of alveolar
Erythrocyte
type I cell
Diffusion of CO2
Alveolus
Respiratory
membrane
Figure 25.10
Diffusion of O2
Alveolar epithelium
Fused basement membranes
of the alveolar epithelium and
the capillary endothelium
Capillary endothelium
(b)
Capillary
Alveolar Macrophages
• The alveolar macrophage (dust cell),
engulfs any microorganism or particulate
matter that makes its way into the
alveolus.
Lungs and Pleura
• Located in pleural cavities on the lateral sides
of the thorax and separated by the mediastinum
• The pleural cavities and the outer surface of the
lung are lined with a serous membrane called
pleura
• Visceral pleura tightly adheres to the outside of
the lung
• Parietal pleura lines the pleural cavity itself
• These two pleuras are continuous with each
other and the space between them is called the
pleural cavity
Lungs
Figure 25.11
Lungs
• Conical in shape, has a base inferiorly that
rests on the diaphragm and an apex that
is the superior most portion of the lung
• The apex projects just slightly superior and
posterior to the clavicle
• The costal surface comes in contact with
the ribs and the slightly concave
mediastinal surface faces medially
toward the mediastinum
Lungs
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Apex
Superior lobe
Horizontal fissure
Oblique fissure
Oblique fissure
Middle
lobe Cardiac
notch
Lingula
Inferior lobe
Base
Right lung
Left lung
(a) Lateral views
Apex
Superior lobe
Oblique fissure
Oblique fissure
Pulmonary arteries
Hilum
Hilum
Primary bronchi
Horizontal fissure
Middle lobe
Pulmonary
veins
Cardiac impression
Inferior lobe
Oblique fissure
Cardiac notch
Oblique fissure
Base
Figure 25.12
Right lung
Left lung
(b) Medial views
Lungs
• The mediastinal surface houses a concave
region called the hilum.
• Bronchi, pulmonary vessels, lymphatic
vessels, and nerves pass into and out of
the lungs in this region.
• Collectively, all structures within the hilum
are termed the root of the lung.
Left Lung
• Slightly smaller than right lung because heart
projects slightly to the left of midline
• Heart makes a medial surface indentation called
the cardiac impression
• Has an anterior indented region called the
cardiac notch
• Has an oblique fissure that divides the lung into
two lobes (superior and inferior lobes)
• The lingula is homologous to the middle lobe of
the right lung
Lungs
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Apex
Superior lobe
Horizontal fissure
Oblique fissure
Oblique fissure
Middle
lobe Cardiac
notch
Lingula
Inferior lobe
Base
Right lung
Left lung
(a) Lateral views
Apex
Superior lobe
Oblique fissure
Oblique fissure
Pulmonary arteries
Hilum
Hilum
Primary bronchi
Horizontal fissure
Middle lobe
Pulmonary
veins
Cardiac impression
Inferior lobe
Oblique fissure
Cardiac notch
Oblique fissure
Base
Figure 25.12
Right lung
Left lung
(b) Medial views
Right Lung
• Has two fissures, oblique and horizontal
fissures that divide the lung into three
lobes (superior, middle and inferior
lobes)
Bronchopulmonary Segments
• There are 10 bronchopulmonary
segments in the right lung and 8–10 in the
left lung.
• Each segment is supplied by its own
tertiary bronchus and a branch of a
pulmonary artery and vein.
• Each segment is surrounded by and
isolated from other segments by
connective tissue.
Bronchopulmonary Segments
Figure 25.13
Blood Supply to and
from the Lungs
•
•
The pulmonary circulation (see figure
23.22) conducts blood to and from the
gas exchange surfaces of the lungs.
The bronchial circulation is a
component of the systemic circulation
that delivers blood directly to and from
the bronchi and bronchioles.
Lymphatic Drainage
• Lymph nodes and vessels are located within the
lungs and around the bronchi and pleura.
• Lymph nodes collect particulate matter.
• Lymph first goes to the pulmonary lymph
nodes within the lungs.
• Lymph then goes to the bronchopulmonary
lymph nodes at the hilum of the lung.
• Lymph then goes to the tracheobronchial
lymph nodes and then into the left and right
bronchomediastinal trunks (see Chapter 24).
Lymphatic Drainage
Figure 25.14
Pulmonary Ventilation
• Breathing, also known as pulmonary
ventilation, is the movement of air into
and out of the respiratory system.
• Movement of gases follows Boyle’s law.
• During inhalation, the volume of the
thoracic cavity increases, intrapulmonary
pressure decreases, and air flows into the
lungs.
• During exhalation, the opposite is true.
Thoracic Wall Dimensional
Changes During Respiration
During inhalation and exhalation, the
thoracic cavity changes in all three
dimensions:
• Vertical—movement of the diaphragm
• Lateral—muscles attached to ribs
• Anterior/Posterior—muscles attached to
ribs
Muscles attached to ribs that aid in lateral and
anterior/posterior changes of the ribs are as follows:
• Scalene=Forced inhalation
•Pectoralis minor=Forced inhalation
•Sternocleidomastoid=Forced inhalation
• External intercostal=normal inhalation
• Internal intercostal=Forced exhalation
• Transverse thoracis=normal exhalation
• Serratus posterior superior=normal inhalation
• Serratus posterior inferior=normal exhalation
•Abdominals=active exhalation
Thoracic Wall Dimensional
Changes During Respiration
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Inhalation
Exhalation
Thoracic
cavity
Thoracic
cavity
Vertical
changes
Diaphragm contracts; vertical
dimensions of thoracic cavity increase.
Diaphragm relaxes; vertical
dimensions of thoracic cavity narrow.
Lateral
changes
Ribs are elevated and thoracic cavity widens.
Ribs are depressed and thoracic cavity narrows.
Anterior-posterior
changes
Figure 25.15
Inferior portion of sternum moves anteriorly.
Inferior portion of sternum moves posteriorly.
Muscles Involved
in External Respiration
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(a) Inhalation
Scalene muscles
elevate 1st and 2nd ribs
External intercostal
muscles elevate ribs
Inferior part of
sternum moves
anteriorly
Diaphragm moves
inferiorly during
contraction
(b) Exhalation
Transversus thoracis
depresses ribs
Internal intercostal
muscles depress ribs
Inferior part of
sternum moves
posteriorly
Diaphragm moves
superiorly as it relaxes
a(2)-b(2): © SIU/Visuals Unlimited
Figure 25.16
Innervation of the
Respiratory System
• The larynx, trachea, bronchial tree, and lungs
are under autonomic control.
• Sympathetic and parasympathetic fibers form
the pulmonary plexus, which is a weblike
network of nerve fibers that surrounds the
primary bronchi and enter the lungs at the hilum.
• Sympathetic stimulation results in
bronchodilation.
• Parasympathetic stimulation results in
bronchoconstriction.
Respiratory Control Centers
in the Brainstem
• The respiratory rhythmicity center in the
medulla oblongata controls the rate and
depth of breathing.
• The dorsal respiratory group (DRG)
controls inhalation by stimulating muscles
of inspiration.
• The ventral respiratory group (VRG)
controls forced exhalation.
Respiratory Control Centers
in the Brainstem
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Stimulation
Inhibition
Pneumotaxic center
Pons
Apneustic center
Respiratory
rhythmicity
center
Ventral respiratory group
(VRG)
Dorsal respiratory group
(DRG)
Medulla oblongata
Internal
intercostal
muscles
Figure 25.17
External
intercostal muscles
Diaphragm
Respiratory Control Centers
in the Brainstem
• The pons houses the apneustic center
and the pneumotaxic center.
• Both centers influence the breathing rate
by modifying the activity of the respiratory
rhythmicity center.
• The pneumotaxic center is inhibitory to
both respiration and the apneustic center.
• The apneustic center stimulates the
inspiratory center in the medulla.
Smoking, Emphysema,
and Lung Cancer Part 1
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Dilated, nonfunctional air spaces
(a)
Dilated, nonfunctional alveoli
LM 15x
(b)
a: © CNRI/Photo Researchers, Inc.; b: © The McGraw-Hill Companies, Inc./Photo by Dr. Alvin Telser
Smoking, Emphysema,
and Lung Cancer Part 2
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Squamous cell carcinoma
© Dr. E. Walker/ Photo Researchers, Inc.
Small-cell
carcinoma
© Javier Domingo/Phototake
a: © CNRI/Photo Researchers, Inc.; b: © The McGraw-Hill Companies, Inc./Photo by Dr. Alvin Telser
Development of the
Respiratory System
Figure 25.18
Summary of Respiratory
System Development