The Respiratory System
Chapter 22
The Respiratory System
• Principal function:
– Gas transport
– Gas exchange
Nasal cavity
• Supplies body with oxygen
Nostril
• Disposes of carbon dioxide
Larynx
• Participates in:
– Regulating blood pH
– Has receptors for smell
– Filters inhaled air
– Produces sounds
– Rids body of small amount of
water and heat in exhaled air
Trachea
Carina of
trachea
Right main
(primary)
bronchus
Right lung
Parietal
pleura
Oral cavity
Pharynx
Left main
(primary)
bronchus
Bronchi
Alveoli
Left lung
Diaphragm
Functional Anatomy of Respiratory System
• Upper Respiratory system:
– Nose, nasal cavity, paranasal sinuses
– Pharynx (throat)
• Lower respiratory system:
– Larynx (boice box)
– Trachea (windpipe)
– Bronchi and smaller branches
– Lungs and alveoli
Respiratory System – functionally consists of
two zones
• Conducting zone
– Nose, nasal cavity, pharynx, larynx,
trachea, bronchi, bronchioles,
terminal bronchioles
– Function: filter, warm, moisten and
conduct air to the lungs
• Respiratory zone
– Respiratory bronchioles, alveolar
ducts, alveolar sacs, alveoli
– Function: gas exchange between air
and blood
The Nose and Nasal Cavity
• The Nose:
–
–
–
–
–
Provides an airway for respiration
Moistens and warms air
Filters inhaled air
Resonating chamber for speech
Houses olfactory receptors
• The Nasal Cavity
– External nares—nostrils
– Divided by nasal septum
– Conchae subdivides each side of the nasal cavity
• Particulate matter deflected to mucus-coated
surfaces
– Continuous with nasopharynx
• Posterior nasal apertures—choanae
The Nose
• Size variation due to differences in nasal cartilages
• Skin is thin—contains many sebaceous glands
Frontal bone
Epicranius,
frontal belly
Root and bridge
of nose
Dorsum nasi
Ala of nose
Apex of nose
Naris (nostril)
Philtrum
(a) Surface anatomy
Nasal bone
Septal cartilage
Maxillary bone
(frontal process)
Lateral process of
septal cartilage
Minor alar
cartilages
Dense fibrous
connective tissue
Major alar
cartilages
(b) External skeletal framework
Figure 22.2
The Upper Respiratory Tract
Cribriform plate
of ethmoid bone
Sphenoid sinus
Posterior nasal
aperture
Nasopharynx
Pharyngeal tonsil
Opening of
pharyngotympanic
tube
Uvula
Oropharynx
Palatine tonsil
Isthmus of the
fauces
Laryngopharynx
Esophagus
Trachea
Frontal sinus
Nasal cavity
Nasal conchae
(superior, middle
and inferior)
Nasal meatuses
(superior, middle,
and inferior)
Nasal vestibule
Nostril
Hard palate
Soft palate
Tongue
Larynx
Epiglottis
Vestibular fold
Thyroid cartilage
Vocal fold
Cricoid cartilage
Thyroid gland
Lingual tonsil
Hyoid bone
Figure 22.3c
Nasal Cavity
• Mucous membrane lines the nasal cavity and conchae:
– Olfactory mucosa
• Near roof of nasal cavity
• Houses olfactory (smell) receptors
– Respiratory mucosa
• Lines nasal cavity
• Epithelium is pseudostratified ciliated columnar
– Goblet cells within epithelium
– Underlying layer of lamina propria
– Cilia move contaminated mucus posteriorly
Paranasal sinuses
• Nasal cavity divided by a septum: nasal septum formed by the septal
nasal cartilage
– Attaches to the vomer and perpendicular plate of the ethmoid bone
• Paranasal sinuses: frontal, sphenoidal, maxillary, ethmoidal
Copyright 2012, John Wiley & Sons,
Inc.
Pharynx
• Funnel-shaped tube ~13 cm (5 in.): starts at internal nares
– Ends at cricoid cartilage (most inferior of the larynx)
– Muscles innervated by cranial nerves IX and X
• Functions of the pharynx
– Passageway for air and food
– Provides a resonating chamber for speech sounds
– Houses the tonsils
• The pharynx can be divided into three anatomical regions
– Nasopharynx: respiratory pathway; pharyngeal tonsil (adenoid)
– Oropharynx: both a respiratory and a digestive pathway
• Fauces (throat); palatine and lingual tonsils
– Laryngopharynx: both a respiratory and a digestive pathway
Nose and Pharynx
Larynx (Voice Box)
• Connects the laryngopharynx with the trachea
• The wall of the larynx is composed of nine cartilage
– Three occur singly (thyroid cartilage, epiglottis, and cricoid cartilage)
– Three occur in pairs (arytenoid, cuneiform, and corniculate cartilages)
• The arytenoid cartilages are the true vocal cords
The Larynx
Body of hyoid bone
• Three functions
– Voice production
– Provides an open airway
– Routes air and food into the proper
channels
• Superior opening closed during
swallowing and open during breathing
Laryngeal prominence
(Adam’s apple)
Cricoid cartilage
Sternal head
Clavicular head
Sternocleidomastoid
Clavicle
Jugular notch
(a) Surface view
Epiglottis
Body of hyoid bone
Thyrohyoid
membrane
Thyroid cartilage
Laryngeal prominence
(Adam’s apple)
Cricothyroid ligament
Cricoid cartilage
Cricotracheal ligament
Tracheal
cartilages
Figure 22.5a, b
The Structures of Voice Production
• Membrane of the larynx forms two
pair of folds
– Ventricular folds (superior pair): false vocal
cords
– Vocal folds (inferior pair): true vocal cords
• Air passing through the larynx
vibrates the folds and produces
sound
• Variation in pitch related to the
tension in the vocal folds
Movements of the Vocal Folds
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
Figure 22.6
Anatomy of the Larynx
Epiglottis
Thyrohyoid
membrane
Hyoid bone
• Sphincter function of the larynx
– Valsalva’s maneuver: straining
• Innervation of the larynx
Corniculate cartilage
Arytenoid cartilage
Thyroid
cartilage
Cricoid cartilage
Glottis
– Recurrent laryngeal nerves (branch
of vagus)
Tracheal cartilages
c) Cartilaginous framework of the larynx, posterior view
Epiglottis
Thyrohyoid
membrane
Cuneiform cartilage
Corniculate cartilage
Arytenoid cartilage
Arytenoid muscle
Cricoid cartilage
Body of hyoid bone
Thyrohyoid membrane
Fatty pad
Vestibular fold
(false vocal cord)
Thyroid cartilage
Vocal fold
(true vocal cord)
Cricothyroid ligament
Cricotracheal ligament
Tracheal cartilages
(d) Sagittal section (anterior on the right)
Figure 22.5c, d
The Trachea
• Descends into the mediastinum
– Smooth muscle and glands of trachea innervated by CN X
• C-shaped cartilage rings keep airway open
• Carina marks where trachea divides into two primary bronchi
– Epithelium: pseudostratified ciliated columnar
Posterior
Mucosa
Esophagus
Trachealis
muscle
Lumen of
trachea
Submucosa
Seromucous gland
in submucosa
Hyaline cartilage
Adventitia
Anterior
(a) Cross section of the trachea and esophagus
Bronchi in the Conducting Zone
Superior lobe
of right lung
Trachea
Superior lobe- left lung
Left main (primary)
bronchus
Lobar (secondary)
bronchus
Segmental (tertiary)
bronchus
Inferior lobe -left lung
Middle lobe
Inferior lobe
of right lung
of right lung
(a) The branching of the bronchial tree
Figure 22.8a
The Bronchial Tree
• Divides into right and left primary bronchi
at the carina
• Bronchi divide to form secondary (lobar)
bronchi, one for each lobe of the lung
– Right lung: three lobes (3 lobar bronchi)
– Left lung: two lobes (2 lobar bronchi)
• Lobar branches into tertiary (segmental)
bronchi
– Segmental divides into bronchioles that branch
repeatedly
– Smallest bronchioles branch into the terminal
bronchioles (contain Clara cells)
Copyright 2012, John Wiley & Sons,
Inc.
The Bronchial Tree
Copyright 2012, John Wiley & Sons,
Inc.
Changes in Tissue Composition
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 under parasympathetic direction
Structures of the Respiratory Zone
• Consists of air-exchanging structures
• Respiratory bronchioles—branch from terminal bronchioles
– Lead to alveolar ducts that lead to alveolar sacs
Alveoli
Alveolar duct
Respiratory
bronchioles
Terminal
bronchiole
Alveolar duct
Alveolar
sac
(a)
Figure 22.9a
Structures of the Respiratory Zone
Respiratory
bronchiole
Alveolar
pores
Alveolar
duct
Alveoli
Alveolar
sac
(b)
Figure 22.9b
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
• Structure of alveoli
– Type I cells: single layer of simple squamous epithelial cells
• Surrounded by basal lamina
• Alveolar and capillary walls plus basal lamina form respiratory
membrane
– Type II cells—scattered among type I cells
• Cuboidal epithelial cells that secrete surfactant
– Reduces surface tension within alveoli
– Alveolar macrophages
Features of Alveoli
• Surrounded by elastic fibers
• Interconnect by way of alveolar pores
• Internal surfaces – site for free movement of alveolar macrophages
Terminal bronchiole
Respiratory bronchiole
Smooth
muscle
Elastic
fibers
Alveolus
Capillaries
(a) Diagrammatic view of capillary-alveoli relationships
Figure 22.10a, b
Anatomy of Alveoli and 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
Type I cell
in capillary
of alveolar wall
Alveoli (gas-filled
Type II (surfactantair spaces)
secreting) 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
Figure 22.10c
Gross Anatomy of the Lungs
• Major landmarks – apex, base, hilum, and root
• Left lung – superior and inferior lobes; oblique fissure
• Right lung – superior, middle, and inferior lobes; horizontal and
oblique fissures
Intercostal muscle
Apex of lung
Rib
Parietal pleura
Pleural cavity
Visceral pleura
Lung
Pulmonary
artery
Trachea
Thymus
Apex of lung
Right superior lobe
Horizontal fissure
Right middle lobe
Oblique fissure
Left
superior lobe
Oblique
fissure
Left inferior
lobe
Right inferior lobe
Heart
(in mediastinum)
Diaphragm
Cardiac notch
Base of lung
(a) Anterior view. The lungs flank mediastinal structures laterally.
Left
superior lobe
Left main
bronchus
Oblique
fissure
Pulmonary
vein
Impression
of heart
Oblique
fissure
Left inferior
lobe
Hilum
Aortic
impression
Lobules
(b) Photograph of medial view of the left lung
Figure 22.11a, b
Bronchopulmonary Segments
Right lung
Left lung
Right
superior
lobe (3
segments)
Left superior
lobe
(4 segments)
Right
middle
lobe (2
segments)
Right
inferior lobe
(5 segments)
Figure 22.12
Left inferior
lobe
(5 segments)
Blood Supply and Innervation of the Lungs
• Pulmonary arteries – deliver oxygen-poor blood to the lungs
• Pulmonary veins – carry oxygenated blood to the heart
• Innervation – sympathetic, parasympathetic, and visceral
sensory fibers
– Parasympathetic—constrict airways
– Sympathetic—dilate airways
Superior Thorax
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.
Figure 22.11d
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
Diagram of the Pleurae and Pleural Cavities
Intercostal muscle
Rib
Parietal pleura
Pleural cavity
Visceral pleura
Lung
Trachea
Thymus
Apex of lung
Right superior lobe
Horizontal fissure
Right middle lobe
Oblique fissure
Left
superior lobe
Oblique
fissure
Left inferior
lobe
Right inferior lobe
Heart
(in mediastinum)
Diaphragm
Cardiac notch
Base of lung
(a) Anterior view. The lungs flank mediastinal structures laterally.
Figure 22.11a
Location of Lungs in Thoracic Cavity
• Four processes involved in respiration
–
–
–
–
Pulmonary ventilation
External respiration
Transport of respiratory gases
Internal respiration
Clavicle
Lung
Rib 3
4
Rib
8
Nipple
9
5
Lung
6
7
10
11
12
Parietal
pleura
8
Midaxillary
line
9
10
Midclavicular line
(a) Posterior view
(b) Anterior view
Infrasternal Angle at
xiphisternal joint
Parietal
pleura
Costal margin
Figure 22.13
The Mechanisms of Ventilation
• Two phases of pulmonary ventilation
– Inspiration: inhalation
– Expiration: exhalation
• Inspiration – volume of thoracic cavity increases
– Decreases internal gas pressure
– Contraction of the diaphragm (flattens)
– Contraction of intercostal muscles raises the ribs
• Deep inspiration requires
– Scalenes, sternocleidomastoid, pectoralis minor, and erector spinae
group (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 and 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.
Figure 22.14
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
Figure 22.15
Neural Control of Ventilation
• Respiratory center – generates baseline respiration rate
– In the reticular formation of the medulla oblongata
• VRG (ventral respiratory group) – most important respiratory
center
– Neurons generate respiratory rhythm
Respiratory Centers in the Brain Stem
Pons
Medulla
Ventral respiratory group (VRG)
contains rhythm generators
whose output drives respiration.
Pons
Medulla
To inspiratory
muscles
Pontine respiratory centers
interact with the medullary
respiratory centers to smooth
the respiratory pattern.
Dorsal respiratory group (DRG)
integrates peripheral sensory
input and modifies the rhythms
generated by the VRG.
Diaphragm
External intercostal
muscles
Figure 22.16
Location of Peripheral Chemoreceptors
• Chemoreceptors
– Sensitive to rising and falling
oxygen levels
• Central chemoreceptors
—located in medulla
• Peripheral chemoreceptors
– Aortic bodies
– Carotid bodies
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
Figure 22.17
Disorders of Lower Respiratory Structures
• Bronchial asthma – type of allergic inflammation
– Hypersensitivity to irritants in the air or to stress
– Asthma attacks characterized by contraction of bronchiole smooth
muscle and secretion of mucus in airways
• Cystic fibrosis (CF)—inherited disease
– Exocrine gland function is disrupted
– Respiratory system affected by oversecretion of viscous mucus
• Chronic obstructive pulmonary disease (COPD) – airflow into
and out of the lungs is difficult
– Obstructive emphysema and chronic bronchitis
– History of smoking
Disorders of Lower Respiratory Structures
Figure 22.18
Alveolar Changes in Emphysema
Figure 22.19
Disorders of Upper Respiratory Structures
• Epistaxis—nosebleed
The Respiratory System Throughout Life
• By week 4 of development:
– Olfactory placodes appear
• Invaginate to form olfactory pits
– Laryngotracheal bud
• Forms trachea, bronchi, and bronchi subdivisions
• Reaches functional maturity late in development
• At birth, only one-sixth of alveoli are present
• Those who begin smoking as teenagers
– Lungs never fully develop
– Additional alveoli never form
The Respiratory System Throughout Life
Future mouth
Pharynx
Frontonasal elevation
Eye
Olfactory placode
Foregut
Stomodeum
(future mouth)
Olfactory
placode
Esophagus
Liver
(a) 4 weeks: anterior
superficial view of
the embryo’s head
Trachea
Laryngotracheal Bronchial
bud
buds
(b) 5 weeks: left lateral view of the developing lower
respiratory passageway mucosae
Figure 22.20
Aging and the Respiratory System
• Aging results in decreased vital capacity, decreased blood level of O2,
and diminished alveolar macrophage activity
• The elderly are more susceptible to pneumonia, emphysema,
bronchitis, and other pulmonary disorders
Aging and the Respiratory System
• Emphysema (em′-fi-SĒ-ma = blown up or full of air): disorder
characterized by destruction of the walls of the alveoli
– Produces abnormally large air spaces that remain filled with air during
exhalation
– With less surface area for gas exchange, O2 diffusion across the respiratory
membrane is reduced
– Blood O2 level is lowered, and any mild exercise that raises the O2 requirements
of the cells leaves the patient breathless
– As increasing numbers of alveolar walls are damaged, lung elastic recoil
decreases due to loss of elastic fibers, and an increasing amount of air becomes
trapped in the lungs at the end of exhalation
– Over several years, added respiratory exertion increases the size of the chest
cage, resulting in a “barrel chest”
– Emphysema is a common precursor to the development of lung cancer
Aging of the Respiratory System
• Number of glands in the nasal mucosa declines
• Nose dries – produces thickened mucus
• Thoracic wall becomes more rigid
• Lungs lose elasticity
• Oxygen levels in the blood may fall