The Respiratory System
Basic functions of the respiratory system
• Breathing (Pulmonary Ventilation) – movement of air in and out of the lungs
Inhalation (inspiration) draws gases into the lungs.
Exhalation (expiration) forces gases out of the lungs.
• Gas Conditioning – as gases pass through the nasal cavity and paransal
sinuses, inhaled air becomes turbulent. The gases in the air are
• warmed to body temperature
• humidified
• cleaned of particulate matter
• Gas Exchange - respiration
• Supplies body with oxygen
• Disposes of carbon dioxide
• Produces Sounds
• Protects respiratory surfaces
• Site for olfactory sensation
Respiration – four distinct processes must happen
• Pulmonary ventilation – moving air into and out of
the lungs
External respiration – gas exchange between the
lungs and the blood
Transport – transport of oxygen and carbon dioxide
between the lungs and tissues
Internal respiration – gas exchange between
systemic blood vessels and tissues
Functional Anatomy of the Respiratory System
Respiratory organs
Nose, nasal cavity, and paranasal sinuses
Pharynx, larynx, and trachea
Bronchi and smaller branches
Lungs and alveoli
Organs of the Respiratory System
Figure 21.1
Respiratory System
Consists of
Respiratory muscles – diaphragm and
other muscles that promote ventilation
Respiratory zone – site of external
respiration – respiratory bronchioles,
alveolar ducts, alveolar sacs, and
Conducting zones
• Provides rigid conduits for air to
reach the sites of gas exchange
• Includes nose, nasal cavity,
pharynx, trachea
• Air passages undergo 23 orders of
branching in the lungs
The Nose
Provides an airway for
Moistens and warms air
Filters inhaled air
Resonating chamber for
Houses olfactory receptors
Skin is thin – contains
many sebaceous glands
The Nasal Cavity
• External nares – nostrils
• Divided by – nasal septum
• Vestibule - anterior opening
• Continuous with nasopharynx
• Two types of mucous membrane
Olfactory mucosa - Near roof of
nasal cavity, houses olfactory
(smell) receptors
Respiratory mucosa - Lines nasal
• Epithelium is pseudostratified ciliated
Goblet cells within epithelium
Underlying layer of lamina propria
has glands that contribute to the
mucus layer and blood vessels that
warm the air.
Cilia move contaminated mucus
Nasal Cavity
Nasal Conchae
3 paired bony projections
along the lateral walls of the
nasal cavity
Superior and middle nasal
conchae - part of the ethmoid
Inferior nasal conchae separate bone
Function - Particulate matter
deflected to mucus-coated
The Paranasal Sinuses
Figure 7.11a, b
The Pharynx
Funnel-shaped passageway
Connects nasal cavity and
Shared by the digestive and
respiratory systems
Divided into three sections by
Nasopharynx – superior
Oropharynx – continuous
with the oral cavity
Laryngopharynx – between
the hyoid bone and the
Type of mucosal lining
changes along its length
The Nasopharynx
Superior to the point
where food enters
Only an air passageway
Closed off during
Epithelium consists of
ciliated pseudostratified
epithelium that moves
The Oropharynx
Arch-like entranceway –
Extends from soft palate to
the epiglottis
Epithelium - stratified
squamous epithelium
Two types of tonsils in the
Palatine tonsils – in the
lateral walls of the fauces
Lingual tonsils – covers
the posterior surface of the
The Laryngopharynx
Passageway for both
food and air
Epithelium - stratified
squamous epithelium
Continuous with the
esophagus and larynx
The Larynx
Prevent food and drink from entering the trachea
Passageway for air
Produces Sound
It connects the pharynx to the trachea
Epithelium of the larynx
• Stratified squamous – superior portion
• Pseudostratified ciliated columnar – inferior portion
Nine Cartilages of the Larynx
• Thyroid cartilage - shield-shaped, forms laryngeal prominence
(Adam’s apple)
Three pairs of small cartilages
• Arytenoid cartilages
• Corniculate cartilages
• Cuneiform cartilages
Epiglottis - tips inferiorly during swallowing
The Larynx
• Vocal ligaments of the
• Vocal folds (true vocal
cords) - act in sound
• Vestibular folds (false
vocal cords) - no role in
sound production
Voice production
• Length of the vocal folds
changes with pitch
• Loudness depends on the
force of air across the
vocal folds
The Trachea
Descends into the mediastinum
C-shaped cartilage rings keep airway open
Carina - marks where trachea divides into two primary
Epithelium - pseudostratified ciliated columnar
The Trachea
Figure 21.7a, b
Bronchi in the Conducting Zone
Bronchial tree - extensively
branching respiratory
Primary bronchi (main
• Largest bronchi
• Right main bronchi - wider
and shorter than the left
Secondary (lobar) bronchi
Tertiary (segmental) bronchi branch into each lung segment
Bronchioles - little bronchi,
less than 1 mm in diameter
Terminal bronchioles - less
than 0.5 mm in diameter
• Three on the right
• Two on the left
Tissue Composition of Conducting Zone
• Changes along pathway
• Supportive connective tissues change
• C-shaped rings – trachea, primary bronchi
• Replaced by cartilage plates, secondary & tertiary bronchi
• Epithelium changes
• First, pseudostratified ciliated columnar – trachea
• Replaced by simple columnar - bronchi
• Then simple cuboidal epithelium - bronchioles and
terminal bronchioles
Smooth muscle becomes important at the bronchioles controlled by the ANS (bronchoconstriction and
Lobes and Surfaces of the lungs
Right lung has three lobes
Left lung has two lobes
Concavity on medial surface = cardiac notch
Bronchi enter the lungs at the hilus
The Pleurae
• A double-layered sac surrounding each lung
• Parietal pleura
• Visceral pleura
• Pleural cavity - potential space between the visceral and parietal pleurae
• Pleurae help divide the thoracic cavity
• Central mediastinum
• Two lateral pleural compartments
Structures of the Respiratory Zone
Consists of air-exchanging structures
Respiratory bronchioles – branch from terminal
• Lead to alveolar ducts
• Lead to alveolar sacs
Structures of the Respiratory Zone
Figure 21.9b
Features Of Alveoli
Alveoli cell types
Surrounded by basal laminae and elastic fibers
Interconnect by way of alveolar pores
Internal surfaces - site for free movement of alveolar macrophages
• Type I cells site of gas exchangeand
• Type II cells - secrete surfactant
• Macrophages
Figure 21.10b