The Respiratory System I: Anatomy
 Functions of the Respiratory
System
 The Nasal Cavity and Sinuses
 Pharynx, Larynx, & Trachea
 Respiratory Mucosa
 Lungs: Lobes, Bronchioles, &
Alveoli
 Mechanics of Breathing
• Pressure Relationships
• Inspiration and Expiration
• Lung Compliance
Respiration
 Pulmonary ventilation (breathing):
movement of air into and out
of the lungs
 External respiration: O2 and CO2
exchange between the lungs
and the blood
Respiratory
system
 Transport: O2 and CO2
in the blood
 Internal respiration: O2 and CO2
exchange between systemic blood
vessels and tissues
Circulatory
system
Organs of the Respiratory system
Key Functions
 Pulmonary
ventilation
 External
respiration
 Respiratory gas
transport
 Internal
respiration
External
intercostals
Functional Anatomy
 Respiratory zone: site of gas exchange
• Microscopic structures: respiratory
bronchioles, alveolar ducts, and alveoli
 Conducting zone: conduits to gas exchange
sites
• Includes all other respiratory structures
 Respiratory muscles: diaphragm and other
muscles that promote ventilation
The Respiratory System I: Anatomy
 Functions of the Respiratory System
 The Nasal Cavity and Sinuses
 Pharynx, Larynx, & Trachea
 Respiratory Mucosa
 Lungs: Lobes, Bronchioles, &
Alveoli
 Mechanics of Breathing
• Pressure Relationships
• Inspiration and Expiration
• Lung Compliance
Upper Respiratory Tract
Cribriform plate
of ethmoid bone
Sphenoid sinus
Posterior nasal
aperture
Nasopharynx
Pharyngeal tonsil
Opening of
pharyngotympanic
tube
Uvula
Frontal sinus
Nasal cavity
Nasal conchae
(superior, middle
and inferior)
Nasal meatuses
(superior, middle,
and inferior)
Nasal vestibule
Nostril
Oropharynx
Palatine tonsil
Isthmus of the
fauces
Hard palate
Soft palate
Tongue
Lingual tonsil
Laryngopharynx
Esophagus
Trachea
(c) Illustration
Larynx
Epiglottis
Vestibular fold
Thyroid cartilage
Vocal fold
Cricoid cartilage
Thyroid gland
Hyoid bone
Figure 22.3c
Anatomy of the Nasal Cavity
 Function of respiratory mucosa in nasal cavity
•
Moistens and heats air so lungs are not dehydrated
nor cool the body’s core; cools it on way out
•
Traps incoming foreign particles
 Function of conchae (projections from lateral walls)
•
Increase surface area
•
Increases air turbulence within the nasal cavity
 Nasal cavity is separated from the oral cavity by the palate
•
Anterior hard palate (bone) and posterior soft palate
(muscle)
 Function of the sinuses
•
Lighten the skull
•
Act as resonance chambers for speech
•
Produce mucus that drains into the nasal cavity
•
Cavities within bones surrounding the nasal cavity: frontal,
sphenoid, ethmoid, maxillary bones
hard palate
soft palate
The Respiratory System I: Anatomy
 Functions of the Respiratory System
 The Nasal Cavity and Sinuses
 Pharynx, Larynx, & Trachea
 Respiratory Mucosa
 Lungs: Lobes, Bronchioles, & Alveoli
 Mechanics of Breathing
• Pressure Relationships
• Inspiration and Expiration
• Lung Compliance
Pharynx (Throat)
 Muscular passage from nasal cavity to larynx
 Three regions of the pharynx
• Nasopharynx – superior region behind
nasal cavity- pseudostratified col. epith.
• Oropharynx – middle region behind
mouth, stratified squamous epithelium
• Laryngopharynx – inferior region
attached to larynx
 The oropharynx and laryngopharynx are
common passageways for air and food
 Auditory tubes enter the nasopharynx
 Tonsils of the pharynx
• Pharyngeal tonsil (adenoids) in the
nasopharynx
• Palatine tonsils in the oropharynx
• Lingual tonsils at the base of the tongue
Larynx (Voice Box)
 Function: Routes air and food into
proper channels
 Plays a role in speech
 Made of eight rigid hyaline
cartilages and a spoon-shaped flap of
elastic cartilage (epiglottis)
 Structures of the Larynx
•
•
Thyroid cartilage
o
Largest hyaline cartilage
o
Protrudes anteriorly
(Adam’s apple)
Epiglottis
o
Superior opening of the
larynx
o
Routes food to the
esophagus and air toward
the trachea
o
Vocal cords (vocal folds)
o
Glottis – opening between
vocal cords
Respiratory Mucosa or Epithelium
 Nasal Cavity and Pharynx
• Pseudostratified ciliated columnar epithelium
• Superficial to the lamina propria of connective tissue
• Mucous secretions from goblet cells contain lysozyme and defensins
• Cilia in the nasal cavity move contaminated mucus posteriorly to throat; tracheal
cilia move mucus upward into pharynx
• Bronchi have cartilaginous reinforcement
 Trachea & Bronchi
• Pseudostratified ciliated columnar epithelium
• Cartilaginous support of hyaline cartilage deep to the lamina propria
 Bronchioles
• Simple cuboidal epithelium and cartilage
 Alveoli
• Simple squamous epithelium
Trachea (Windpipe)
 Connects larynx with
bronchi
 Lined with ciliated
mucosa
• Beat continuously in
the opposite
direction of
incoming air
• Expel mucus loaded
with dust and other
debris away from
lungs
 Walls are reinforced with
C-shaped hyaline
cartilage
Mucosa
• Pseudostratified
ciliated columnar
epithelium
• Lamina propria
(connective tissue)
Submucosa
Seromucous gland
in submucosa
Hyaline cartilage
(b) Photomicrograph of the tracheal wall (320x)
Figure 22.6b
The Respiratory System I: Anatomy
 Functions of the Respiratory System
 The Nasal Cavity and Sinuses
 Pharynx, Larynx, & Trachea
 Respiratory Mucosa
 Lungs: Lobes, Bronchioles, &
Alveoli
 Mechanics of Breathing
• Pressure Relationships
• Inspiration and Expiration
• Lung Compliance
Lungs
 Occupy most of the thoracic
cavity
• Apex is near the clavicle
(superior portion)
o Base rests on the diaphragm
(inferior portion)
• Each lung is divided into
lobes by fissures
o Left lung – two lobes
o Right lung – three lobes
Diaphragm
Lungs: Primary Bronchi
 Formed by division of the trachea
 Enters the lung at the hilus (medial depression)
 Right bronchus is wider, shorter, and straighter than left
•  More likely to get infections in right lung than left
 Bronchi subdivide into smaller and smaller branches (with rings)
Lungs: Linings (Pleura)
• Thin, doublelayered serosa
• Pleural fluid
provides
lubrication and
surface tension
Respiratory Tree Divisions
 Primary bronchi
 Secondary bronchi
 Tertiary bronchi
 Bronchioles
Bronchioles
 Bronchioles end in
terminal bronchioli
• All but the smallest
branches have
reinforcing cartilage
• Lined with simple
cuboidal epithelium
 Terminal bronchioles end
in alveoli
Capillaries Surround Alveoli to Pick Up O2 and Deliver CO2
Terminal bronchiole
Respiratory bronchiole
Smooth
muscle
Elastic
fibers
Alveolus
Capillaries
Figure 22.9a
Respiratory
bronchiole
Alveolar
duct
Alveolar
pores
Alveoli
(b)
Alveolar
sac
Figure 22.8b
Alveolar Structure and Cellular Composition
(The Respiratory Membrane)
Red blood
cell
Nucleus of type I
(squamous
epithelial) cell
Alveolar pore
Capillary
O2
Capillary
CO2
Alveolus
Alveolus
Type I cell
of alveolar wall
Macrophage
Endothelial cell nucleus
Respiratory
membrane
Red blood cell
Alveoli (gas-filled in capillary
Type II (surfactantair spaces)
secreting) cell
Type II cells also secrete
antimicrobial proteins
Alveolar
epithelium
Fused basement
membranes of the
alveolar epithelium
and the capillary
endothelium
Capillary
endothelium
External respiration: O2 and CO2 flow easily down
their concentration gradients, into and out of alveoli
across thin, simple squamous epithelium
Figure 22.9c
The Respiratory System I: Anatomy
 Functions of the Respiratory System
 The Nasal Cavity and Sinuses
 Pharynx, Larynx, & Trachea
 Respiratory Mucosa
 Lungs: Lobes, Bronchioles, &
Alveoli
 Mechanics of Breathing
• Pressure Relationships
• Inspiration and Expiration
• Lung Compliance
Pressure Relationships in the Thoracic Cavity
 Respiratory pressures are described relative to Patm
• A negative respiratory pressure is less than Patm
• A positive respiratory pressure is greater than Patm
• Zero respiratory pressure = Patm = 760 Hg at sea
level
Intrapulmonary and Intrapleural Pressures
 Intrapulmonary (intra-alveolar) pressure (Ppul)
• Pressure in the alveoli
• Fluctuates with breathing
• Always eventually equalizes with Patm
 Intrapleural pressure (Pip):
• Pressure in the pleural cavity that fluctuates with
breathing
• Expressed as a negative pressure (less than Patm and
Ppul), caused by opposing forces:
• Elastic lung recoil and alveolar surface tension are forces that
promote lung collapse (when Pip = Ppul, lungs collapse)
• Elasticity of the chest wall pulls the thorax outward; promotes
lung expansion
Lungs are Inflated if Transpulmonary Pressure > 0
Atmospheric pressure
Parietal pleura
Thoracic wall
Visceral pleura
Pleural cavity
Intrapleural
pressure
756 mm Hg
(–4 mm Hg)
Intrapulmonary
756
pressure 760 mm Hg
760
Lung
Diaphragm
(Relative to Patm= 0 mm Hg)
Transpulmonary
pressure
760 mm Hg
–756 mm Hg
= 4 mm Hg
Figure 22.12
The Respiratory System I: Anatomy
 Functions of the Respiratory System
 The Nasal Cavity and Sinuses
 Pharynx, Larynx, & Trachea
 Respiratory Mucosa
 Lungs: Lobes, Bronchioles, & Alveoli
 Mechanics of Breathing
• Pressure Relationships
• Inspiration and Expiration
• Lung Compliance
Pulmonary Ventilation: Expanding and Contracting the Lungs
 Subdivided into inspiration and expiration
• Mechanical processes that depend on volume
changes in the thoracic cavity
• Can use Boyle’s Law to understand
• P1V1 = P2V2
• Volume changes cause pressure changes
• If the volume of the lungs increases, the air
pressure within them decreases
• Pressure changes cause gases flow to equalize
pressure
Inspiration: An Active Process
Sequence of events
Changes in anteriorposterior and superiorinferior dimensions
Changes in lateral
dimensions
(superior view)
1 Inspiratory muscles
contract (diaphragm
descends; rib cage rises).
2 Thoracic cavity volume
increases.
Ribs are elevated
and sternum flares
as external
intercostals
contract.
3 Lungs are stretched;
External
intercostals
contract.
intrapulmonary volume
increases.
4 Intrapulmonary pressure
drops below Patm (–1 mm Hg).
5 Air (gases) flows into
lungs down its pressure
gradient until intrapulmonary
pressure is 0 (equal to
atmospheric pressure).
Diaphragm
moves inferiorly
during contraction.
Figure
22.13
(1 of 2)
Expiration: Normally a Passive Process
Sequence
of events
Changes in anteriorposterior and superiorinferior dimensions
Changes in
lateral dimensions
(superior view)
1 Inspiratory muscles
relax (diaphragm rises; rib
cage descends due to
recoil of costal cartilages).
2 Thoracic cavity volume
Ribs and sternum
are depressed
as external
intercostals
relax.
decreases.
3 Elastic lungs recoil
External
intercostals
relax.
passively; intrapulmonary
volume decreases.
4
Intrapulmonary
pressure
rises above Patm (+1 mm Hg).
5 Air (gases) flows out of
lungs down its pressure
gradient until intrapulmonary pressure is 0.
Diaphragm
moves
superiorly
as it relaxes.
Forced expiration is an active process: it uses
abdominal and internal intercostal muscles
Pressure anim. I online
Pressure anim II online
Figure 22.13 (2 of 2)
Atelectasis
 Atelectasis (lung collapse)
• Plugged bronchioles  collapse of alveoli
• Wound that admits air into pleural cavity
(pneumothorax)
The Respiratory System I: Anatomy
 Functions of the Respiratory System
 The Nasal Cavity and Sinuses
 Pharynx, Larynx, & Trachea
 Respiratory Mucosa
 Lungs: Lobes, Bronchioles, &
Alveoli
 Mechanics of Breathing
• Pressure Relationships
• Inspiration and Expiration
• Lung Compliance
Physical Factors Influencing Pulmonary Ventilation
 Three factors that must be overcome by inspiratory
muscles
1. Airway resistance (friction, usually insignificant
if bronchioles wide open, increasing with smaller
diameters)
2. Alveolar surface tension (alleviated by Type II
alveolar cell surfactant)
3. Lung compliance: the change in lung volume
that occurs with a given change in
transpulmonary pressure (lung “stretchiness”)
Lung Compliance: Ease of Lung Expansion
 Compliance is normally high (easily inflated) due to
• Lung tissue is readily distensible (stretched outwards)
• Surfactant alleviates alveolar surface tension
 Compliance is reduced (as in “stiff lungs”) by
• Nonelastic scar tissue (fibrosis)
• Reduced production of surfactant (e.g. death of Type II cells)
• Decreased flexibility of the thoracic cage
 Homeostatic imbalances that reduce compliance
• Paralysis of intercostal muscles
Emphysema
Features of Emphysema
 Chronic inflammation promotes lung
fibrosis (tends to decrease lung
compliance)
 Airways collapse during expiration
 Type II surfactant cells die, reducing
surfactant production and decreasing
compliance
 Alveoli enlarge as adjacent chambers
break through, increasing lung
compliance somewhat (easier to
inflate)
 Patients use a large amount of
energy to exhale, normally a passive
process
 Overinflation of the lungs leads to a
permanently expanded barrel chest
 Cyanosis appears late in the disease
The Respiratory System I: Anatomy
 Functions of the Respiratory System
 The Nasal Cavity and Sinuses
 Pharynx, Larynx, & Trachea
 Respiratory Mucosa
 Lungs: Lobes, Bronchioles, &
Alveoli
 Mechanics of Breathing
• Pressure Relationships
• Inspiration and Expiration
• Lung Compliance