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The Respiratory System
Ch 22
Leonardo Da Vinci
Human Anatomy
Sonya Schuh-Huerta, Ph.D.
The Upper Respiratory Tract
Cribriform plate
of ethmoid bone
Frontal sinus
Nasal cavity
Nasal conchae
(superior, middle
and inferior)
Sphenoid sinus
Posterior nasal
aperture
Nasopharynx
Pharyngeal tonsil
Opening of
pharyngotympanic
tube
Nasal meatuses
(superior, middle,
and inferior)
Nasal vestibule
Nostril
Uvula
Oropharynx
Palatine tonsil
Isthmus of the
fauces
Hard palate
Soft palate
Laryngopharynx
Lingual tonsil
Hyoid bone
Esophagus
Trachea
Tongue
Larynx
Epiglottis
Vestibular fold
Thyroid cartilage
Vocal fold
Cricoid cartilage
Thyroid gland
Organs of the Respiratory System
Nasal cavity
Nostril
Larynx
Trachea
Carina of
trachea
Right main
(primary)
bronchus
Right lung
Parietal
pleura
Oral cavity
Pharynx
Left main
(primary)
bronchus
Bronchi
Alveoli
Left lung
Diaphragm
Bronchi in the Conducting Zone
Superior lobe
of right lung
Trachea
Superior lobe
of left lung
Left main
(primary)
bronchus
Lobar
(secondary)
bronchus
Segmental
(tertiary)
bronchus
Inferior lobe
of left lung
Inferior lobe
of right lung
Middle lobe
of right lung
(a) The branching of the bronchial tree
Structures of the Respiratory Zone
Alveoli
Alveolar duct
Respiratory
bronchioles
Terminal
bronchiole
(a)
Alveolar duct
Alveolar
sac
Alveoli & the Respiratory Membrane
Terminal bronchiole
Respiratory bronchiole
Smooth
muscle
Elastic
fibers
Alveolus
Capillaries
(a) Diagrammatic view of capillary-alveoli relationships
Anatomy of Alveoli & the Respiratory
Membrane
Red blood
cell
Nucleus of type I
(squamous
epithelial) cell
Alveolar pores
Capillary
O2
Macrophage
Endothelial cell nucleus
Alveolus
Respiratory
membrane
Red blood cell
in capillary
Alveoli (gas-filled
air spaces)
Type I cell
of alveolar wall
Type II (surfactantsecreting) cell
(c) Detailed anatomy of the respiratory membrane
Capillary
CO2
Alveolus
Alveolar epithelium
Fused basement
membranes of the
alveolar epithelium
and the capillary
endothelium
Capillary endothelium
The Respiratory System
• Basic functions of the respiratory system
– Supplies body with oxygen
– Disposes of carbon dioxide
• 4 processes involved in respiration:
– Pulmonary ventilation
– External respiration
– Transport of respiratory gases
– Internal respiration
Functional Anatomy of the
Respiratory System
• Respiratory organs
– Nose, nasal cavity, & paranasal sinuses
– Pharynx, larynx, & trachea
– Bronchi & smaller branches
– Lungs & alveoli
Organs of the Respiratory
System
• Divided into
– Conducting zone
– Respiratory zone
The Nose
•
•
•
•
•
Provides an airway for respiration
Moistens & warms air (humidifies air)
Filters inhaled air
Resonating chamber for speech
Houses olfactory receptors (olfaction)
The Nose
• Size variation due to differences in nasal
cartilages
• Skin is thin  contains many sebaceous glands
Frontal bone
Epicranius,
frontal belly
Nasal bone
Root and bridge
of nose
Septal cartilage
Maxillary bone
(frontal process)
Dorsum nasi
Ala of nose
Lateral process of
septal cartilage
Minor alar
cartilages
Apex of nose
Dense fibrous
connective tissue
Naris (nostril)
Major alar
cartilages
Philtrum
(a) Surface anatomy
(b) External skeletal framework
The Nasal Cavity
• External nares  nostrils
• Divided by nasal septum
• Continuous with nasopharynx
Nasal Cavity
• 2 types of mucous membrane:
– Olfactory mucosa
• Near roof of nasal cavity
• Houses olfactory receptors
– Respiratory mucosa
• Lines nasal cavity
• Pseudostratified ciliated columnar epithelium
The Upper Respiratory Tract
Cribriform plate
of ethmoid bone
Frontal sinus
Nasal cavity
Nasal conchae
(superior, middle
and inferior)
Sphenoid sinus
Posterior nasal
aperture
Nasopharynx
Pharyngeal tonsil
Opening of
pharyngotympanic
tube
Nasal meatuses
(superior, middle,
and inferior)
Nasal vestibule
Nostril
Uvula
Oropharynx
Palatine tonsil
Isthmus of the
fauces
Hard palate
Soft palate
Laryngopharynx
Lingual tonsil
Hyoid bone
Esophagus
Trachea
Tongue
Larynx
Epiglottis
Vestibular fold
Thyroid cartilage
Vocal fold
Cricoid cartilage
Thyroid gland
Respiratory Mucosa
• Consists of:
– Pseudostratified ciliated columnar epithelium
– Goblet cells within epithelium
– Underlying layer of lamina propria
• Cilia move contaminated mucus
posteriorly
Nasal Conchae
• Superior & middle nasal conchae
– Part of the ethmoid bone
• Inferior nasal conchae
– Separate bone
• Project medially from the lateral wall of the
nasal cavity
• Particulate matter:
– Deflected to mucus-coated surfaces
The Pharynx
• Funnel-shaped passageway
• Connects nasal cavity & mouth
• Divided into 3 sections by location:
– Nasopharynx
– Oropharynx
– Laryngopharynx
• Type of mucosal lining changes along its
length
The Nasopharynx
•
•
•
•
Superior to the point where food enters
Only an air passageway
Closed off during swallowing
Pharyngeal tonsil (adenoids)
– Located on posterior wall
– Destroys pathogens that enter
• Contains the opening to the pharyngotympanic
tube (auditory or eustachian tube)
– Tubal tonsil
• Provides some protection from infection
The Oropharynx
• Arch-like entrance-way  fauces
– Extends from soft palate to epiglottis
• Epithelium
– Stratified squamous epithelium
• 2 types of tonsils in the oropharynx
– Palatine tonsils  in lateral walls of the fauces
– Lingual tonsils  covers the posterior surface
of the tongue
The Laryngopharynx
• Passageway for both food & air
• Epithelium
– Stratified squamous epithelium
• Continuous with the esophagus & larynx
The Larynx
• 3 functions 
– Voice production
– Provides an open airway
– Routes air & food into the proper channels
• Superior opening (epiglotis) is:
– Closed during swallowing
– Open during breathing
9 Cartilages of the Larynx
• Thyroid cartilage
– Shield-shaped, forms laryngeal prominence
(= Adam’s apple)
• 3 pairs of small cartilages
– Arytenoid cartilages
– Corniculate cartilages
– Cuneiform cartilages
• Epiglottis
– Tips inferiorly during swallowing
The Larynx
• Vocal ligaments of the larynx
– Vocal folds (= true vocal cords)
• Function in sound production
– Vestibular folds (= false vocal cords)
• No role in sound production
• Epithelium of the larynx:
– Stratified squamous  superior portion
– Pseudostratified ciliated columnar  inferior
portion
Anatomy of the Larynx
Body of hyoid bone
Laryngeal prominence
(Adam’s apple)
Cricoid cartilage
Sternal head
Clavicular head
Sternocleidomastoid
Clavicle
Jugular notch
(a) Surface view
Epiglottis
Thyrohyoid
membrane
Body of hyoid bone
Thyroid cartilage
Laryngeal prominence
(Adam’s apple)
Cricothyroid ligament
Cricoid cartilage
Cricotracheal ligament
Tracheal
cartilages
(b) Anterior view
Anatomy of the Larynx
Epiglottis
Thyrohyoid
membrane
Hyoid bone
Corniculate cartilage
Thyroid
cartilage
Arytenoid cartilage
Cricoid cartilage
Glottis
Tracheal cartilages
(c) Photograph of cartilaginous framework of the larynx, posterior view
Epiglottis
Thyrohyoid
membrane
Body of hyoid bone
Thyrohyoid membrane
Cuneiform cartilage
Fatty pad
Corniculate cartilage
Arytenoid cartilage
Vestibular fold
(false vocal cord)
Arytenoid muscle
Cricoid cartilage
Thyroid cartilage
Vocal fold
(true vocal cord)
Cricothyroid ligament
Cricotracheal ligament
Tracheal cartilages
(d) Sagittal section (anterior on the right)
Movements of the Vocal Cords
Anterior
Thyroid cartilage
Cricoid cartilage
Vocal ligaments
of vocal cords
Glottis
Lateral
cricoarytenoid muscle
Arytenoid cartilage
Corniculate cartilage
Posterior
cricoarytenoid muscle
Posterior
Base of tongue
Epiglottis
Vestibular fold
(false vocal cord)
Vocal fold
(true vocal cord)
Glottis
Inner lining of trachea
Cuneiform cartilage
Corniculate cartilage
(a) Vocal folds in closed position; closed glottis
(b) Vocal folds in open position; open glottis
The Larynx
• Voice production
– Length of the vocal folds changes with pitch
– Loudness depends on the force of air across
the vocal folds
• Sphincter function of the larynx
– Valsalva’s maneuver  straining
• Innervation of the larynx
– Recurrent laryngeal nerves (branch of vagus)
The Trachea
• Descends into the mediastinum
• C-shaped cartilage rings keep airway open!
• Carina
– Marks where trachea divides into 2 primary
bronchi
– Epithelium 
• Pseudostratified ciliated columnar epithelium
~remember this?
The Trachea
Mucosa
Pseudostratified
ciliated columnar
epithelium
Lamina propria
(connective tissue)
Submucosa
Seromucous gland
in submucosa
Posterior
Hyaline cartilage
Mucosa
Esophagus
Trachealis
muscle
Submucosa
Lumen of
trachea
Seromucous gland
in submucosa
Hyaline cartilage
Adventitia
Anterior
(a) Cross section of the trachea and esophagus
(b) Photomicrograph of the tracheal wall (250)
Bronchi in the Conducting Zone
• Bronchial tree
– Extensively branching respiratory
passageways
• Primary bronchi (main bronchi)
– Largest bronchi
• Right main primary bronchi
– Wider & shorter than the left
– Right lung also bigger than the left
Bronchi in the Conducting Zone
Superior lobe
of right lung
Trachea
Superior lobe
of left lung
Left main
(primary)
bronchus
Lobar
(secondary)
bronchus
Segmental
(tertiary)
bronchus
Inferior lobe
of left lung
Inferior lobe
of right lung
Middle lobe
of right lung
(a) The branching of the bronchial tree
Bronchi in the Conducting Zone
• Secondary (lobar) bronchi
– Three on the right
– Two on the left
• 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
Bronchi in the Conducting Zone
Mucosa
Pseudostratified
epithelium
Lumen
Lamina propria
Fibromusculocartilaginous
layer
Cartilage plate
Smooth muscle
(b) Photomicrograph of a bronchus (13)
Changes in Tissue Along
Conducting Pathways
• Supportive connective tissues change
– C-shaped rings replaced by cartilage plates
• Epithelium changes
– First, pseudostratified ciliated columnar
– Replaced by simple columnar, then simple
cuboidal epithelium
• Smooth muscle becomes important:
– Airways widen with sympathetic stimulation
– Airways constrict with parasympathetic stim.
Structures of the Respiratory
Zone
• Consists of air-exchanging structures
• Respiratory bronchioles  branch from
terminal bronchioles
– Lead to alveolar ducts
• Lead to alveolar sacs
Structures of the Respiratory Zone
Alveoli
Alveolar duct
Respiratory
bronchioles
Terminal
bronchiole
(a)
Alveolar duct
Alveolar
sac
Structures of the Respiratory Zone
Respiratory
bronchiole
Alveolar
pores
Alveolar
duct
Alveoli
Alveolar
sac
(b)
Structures of the Respiratory
Zone
• Alveoli
– ~300 million alveoli account for tremendous
surface area of the lungs!
• Surface area of alveoli is ~140 square meters!!!
• Why such a large surface area?
Structures of the Respiratory
Zone
• Structure of alveoli
– Type I cells  single layer of simple
squamous epithelial cells
• Surrounded by basal lamina
– Alveolar & capillary walls plus their basal
lamina form
• The Respiratory membrane
Anatomy of Alveoli & the Respiratory
Membrane
Terminal bronchiole
Respiratory bronchiole
Smooth
muscle
Elastic
fibers
Alveolus
Capillaries
(a) Diagrammatic view of capillary-alveoli relationships
Structures of the Respiratory
Zone
• Structures of alveoli (cont.)
– Type II cells  scattered among type I cells
• Are cuboidal epithelial cells
• Secrete  surfactant (very important!)
– Detergent-like molecule, that reduces surface tension
within alveoli (prevents them from collapsing)
– Alveolar macrophages also present
Anatomy of Alveoli & the Respiratory
Membrane
Red blood
cell
Nucleus of type I
(squamous
epithelial) cell
Alveolar pores
Capillary
O2
Macrophage
Endothelial cell nucleus
Alveolus
Respiratory
membrane
Red blood cell
in capillary
Alveoli (gas-filled
air spaces)
Type I cell
of alveolar wall
Type II (surfactantsecreting) cell
(c) Detailed anatomy of the respiratory membrane
Capillary
CO2
Alveolus
Alveolar epithelium
Fused basement
membranes of the
alveolar epithelium
and the capillary
endothelium
Capillary endothelium
The Respiratory Zone
• Features of alveoli
– Surrounded by elastic fibers
– Interconnect by way of alveolar pores
– Internal surfaces
• A site for free movement of alveolar macrophages
Gross Anatomy of the Lungs
• Major landmarks of the lungs
– Apex, base, hilum, & root
• Left lung
– Superior & inferior lobes
• Right lung
– Superior, middle, & inferior lobes
Gross Anatomy of the Lungs
Anterior View of Thoracic Structures
Intercostal muscle
Rib
Lung
Apex of lung
Parietal pleura
Pleural cavity
Visceral pleura
Pulmonary
artery
Trachea
Thymus
Apex of lung
Left
superior lobe
Left
superior lobe
Left main
bronchus
Oblique
fissure
Oblique
fissure
Pulmonary
vein
Left inferior
lobe
Impression
of heart
Right inferior lobe
Heart
(in mediastinum)
Hilum
Oblique
fissure
Diaphragm
Aortic
impression
Right superior lobe
Horizontal fissure
Right middle lobe
Left inferior
lobe
Oblique fissure
Base of lung
Cardiac notch
(a) Anterior view. The lungs flank mediastinal structures laterally.
Lobules
(b) Photograph of medial view of the left lung
Bronchial Tree
Right lung
Right
superior
lobe (3
segments)
Left lung
Left superior
lobe
(4 segments)
Right
middle
lobe (2
segments)
Right
inferior lobe
(5 segments)
Left inferior
lobe
(5 segments)
Blood Supply & Innervation of
the Lungs
• Pulmonary arteries
– Deliver oxygen-poor blood to the lungs
• Pulmonary veins
– Carry oxygenated blood to the heart
• Innervation
– Sympathetic, parasympathetic, & visceral
sensory fibers
• Parasympathetic  constrict airways
• Sympathetic  dilate airways
Transverse Cut Through Lungs
Vertebra
Right lung
Parietal pleura
Visceral pleura
Pleural cavity
Posterior
Esophagus
(in mediastinum)
Root of lung
at hilum
Left main bronchus
Left pulmonary
artery
Left pulmonary vein
Left lung
Thoracic wall
Pulmonary trunk
Pericardial
membranes
Sternum
Heart (in mediastinum)
Anterior mediastinum
Anterior
(d) Transverse section through the thorax, viewed from above. Lungs, pleural
membranes, and major organs in the mediastinum are shown.
The Pleurae (review)
• A double-layered sac surrounding each
lung
– Parietal pleura
– Visceral pleura
• Pleural cavity
– Potential space between the visceral &
parietal pleurae
• Pleurae help divide the thoracic cavity
– Central mediastinum
– 2 lateral pleural compartments
Diagram of the Pleurae & Pleural Cavities
Intercostal muscle
Rib
Parietal pleura
Pleural cavity
Visceral pleura
Lung
Trachea
Thymus
Apex of lung
Left
superior lobe
Right superior lobe
Oblique
fissure
Horizontal fissure
Left inferior
lobe
Right middle lobe
Oblique fissure
Right inferior lobe
Heart
(in mediastinum)
Diaphragm
Base of lung
Cardiac notch
(a) Anterior view. The lungs flank mediastinal structures laterally.
The Mechanisms of Ventilation
• 2 phases of pulmonary ventilation
– Inspiration  inhalation
– Expiration  exhalation
Inspiration
• Volume of thoracic cavity increases
– Decreases internal gas pressure
– Action of the diaphragm
• Diaphragm flattens
– Action of intercostal muscles
• Contraction raises the ribs
Inspiration
• Deep inspiration requires
– Scalenes
– Sternocleidomastoid
– Pectoralis minor
– Erector spinae  extends the back
Expiration
• Quiet expiration  chiefly a passive
process!
– Inspiratory muscles relax
– Diaphragm moves superiorly
– Volume of thoracic cavity decreases
• Forced expiration  an active process
– Produced by contraction of
• Internal & external oblique muscles
• Transverse abdominis muscles
Changes in Thoracic Volume
(a) Inspiration
Diaphragm and intercostal muscles
contract (diaphragm descends and
rib cage rises). Thoracic cavity
volume increases.
Changes in
superiorinferior and
anteriorposterior
dimensions
Ribs are
elevated and
sternum flares
as external
intercostals
contract.
Diaphragm moves
inferiorly during
contraction.
Changes
in lateral
dimensions
(superior
view)
External
intercostals
contract.
(b) Expiration
Inspiratory muscles relax (diaphragm rises and
rib cage descends due to recoil of the costal
cartilages). Thoracic cavity volume decreases.
Ribs and
sternum are
depressed as
external
intercostals
relax.
Diaphragm moves
superiorly as it relaxes.
External
intercostals
relax.
Changes in Thoracic Volume
1 At rest, no air
movement: Air
pressure in lungs is
equal to atmospheric
(air) pressure. Pressure
in the pleural cavity is
less than pressure in the
lungs. This pressure
difference keeps the
lungs inflated.
Trachea
Main bronchi
Thoracic wall
Pleural
cavity
Lung
Lung
3 Expiration: Inspiratory
muscles relax, reducing thoracic
volume, and the lungs recoil.
Simultaneously, volumes of the
pleural cavity and the lungs
decrease, causing pressure to
increase in the lungs, and air
flows out. Resting state is
reestablished.
Pleural Thoracic
cavity wall
Diaphragm
Air
2 Inspiration: Inspiratory
muscles contract and increase
the volume of the thoracic and
pleural cavities. Pleural fluid in
the pleural cavity holds the
parietal and visceral pleura close
together, causing the lungs to
expand. As volume increases,
pressure decreases and air flows
into the lungs.
Parietal
pleura
Visceral
pleura
At rest
V
P
Expanded
V
P
Air flows in
Air
V
P
Air flows
out
V
P
Neural Control of Ventilation
• Respiratory center
– Generates baseline respiration rate
– In the reticular formation of the medulla
oblongata
• Chemoreceptors
– Sensitive to rising & falling oxygen levels
– Central chemoreceptors  located in
medulla
– Peripheral chemoreceptors
• Aortic bodies
• Carotid bodies
Location of Peripheral Chemoreceptors
Brain
Sensory nerve fiber in cranial nerve
IX (pharyngeal branch
of glossopharyngeal)
External carotid artery
Internal carotid artery
Carotid body
Common carotid artery
Cranial nerve X (vagus nerve)
Sensory nerve fiber in
cranial nerve X
Aortic bodies in aortic arch
Aorta
Heart
Disorders of Lower Respiratory
Structures
• Bronchial asthma
– A type of allergic inflammation
• Hypersensitivity to irritants in the air or to stress
– Asthma attacks characterized by
• Contraction of bronchiole smooth muscle
• Secretion of mucus in airways
Disorders of Lower Respiratory
Structures
• Cystic fibrosis (CF)  inherited disease
– Exocrine gland function is disrupted
– Respiratory system affected by
• Oversecretion of viscous mucus
• Pneumonia  infectious disease
– Accumulation of fluid in alveoli
– Interferes with gas exchange (drowning)
Disorders of Lower Respiratory
Structures
• Chronic obstructive pulmonary disease
(COPD)
– Airflow into & out of the lungs is difficult
• Obstructive emphysema
• Chronic bronchitis
– History of smoking usually associated
Disorders of Lower Respiratory Structures
Figure 22.18
Alveolar Changes in Emphysema
Figure 22.19
Lung Cancer
• Most common cause of
cancer-related death!
– 1.3 million deaths/year worldwide
– Treated by surgery, radiation, and/or
chemotherapy
– Symptoms  shortness of
breath, coughing (up blood),
weight loss
– History of smoking or 2ndhand smoke usually associated
– 14% survival rates
Aging of the Respiratory System
• The number of glands in nasal mucosa declines
• Nose dries
– Produces thickened mucus
• Thoracic wall becomes more rigid
• Lungs lose elasticity
• Oxygen levels in the blood may fall
• Again…Exercise throughout life important
for respiratory health!
Questions…?
What’s Next?
Wed Lecture: Lecture Exam 4!
Wed Lab: Start Digestive System
Mon Lecture: Digestive Sys.
& class Potluck!
~We’ll eat while we learn about eating & digestion