1. 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

2. 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
Transport: O2 and CO2 in the blood
Internal respiration: O2 and CO2 exchange between systemic blood vessels and tissues
Respiratory
system
Circulatory
system

3. Organs of the Respiratory system
Key Functions
Pulmonary ventilation
External respiration
Respiratory gas transport
Internal respiration
External intercostals

4. 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

5. 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

6. Upper Respiratory Tract
Cribriform plate
of ethmoid bone
Frontal sinus
Sphenoid sinus
Posterior nasal
aperture
Nasal cavity
Nasal conchae
(superior, middle
and inferior)
Nasopharynx
Pharyngeal tonsil
Nasal meatuses
(superior, middle,
and inferior)
Opening of
pharyngotympanic
tube
Nasal vestibule
Uvula
Nostril
Oropharynx
Hard palate
Palatine tonsil
Soft palate
Isthmus of the
fauces
Tongue
Lingual tonsil
Laryngopharynx
Hyoid bone
Larynx
Epiglottis
Esophagus
Vestibular fold
Thyroid cartilage
Vocal fold
Cricoid cartilage
Trachea
Thyroid gland
(c) Illustration
Figure 22.3c

7. 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
hard palate soft palate
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

8. 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

9. 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
Figure 22.3b

10. 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
Largest hyaline cartilage
Protrudes anteriorly (Adam’s apple)
Epiglottis
Superior opening of the larynx
Routes food to the esophagus and air toward the trachea
Vocal cords (vocal folds)
Glottis – opening between vocal cords

11. 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
Cartilaginous support of hyaline cartilage deep to the lamina propria
Bronchioles
Simple cuboidal epithelium and cartilage
Alveoli
Simple squamous epithelium

12. 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

13. (b) Photomicrograph of the tracheal wall (320x)
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

14. 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

15. Lungs Occupy most of the thoracic cavity
Apex is near the clavicle (superior portion)
Base rests on the diaphragm (inferior portion)
Each lung is divided into lobes by fissures
Left lung – two lobes
Right lung – three lobes
Diaphragm

16. 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)

17. Lungs: Linings (Pleura)
Thin, double-layered serosa
Pleural fluid provides lubrication and surface tension

18. Respiratory Tree Divisions
Primary bronchi
Secondary bronchi
Tertiary bronchi
Bronchioles

19. Bronchioles Bronchioles end in terminal bronchioli
All but the smallest branches have reinforcing cartilage
Lined with simple cuboidal epithelium
Terminal bronchioles end in alveoli

20. Capillaries Surround Alveoli to Pick Up O2 and Deliver CO2
Terminal bronchiole
Respiratory bronchiole
Smooth
muscle
Elastic
fibers
Alveolus
Capillaries
Figure 22.9a

21. Respiratory bronchiole Alveolar Alveolar duct pores Alveoli Alveolar
sac
(b)
Figure 22.8b

22. Alveolar Structure and Cellular Composition (The Respiratory Membrane)
Red blood
cell
Nucleus of type I
(squamous
epithelial) cell
Alveolar pore
Capillary O2
Capillary
Type I cell
of alveolar wall
CO2
Alveolus
Macrophage
Alveolus
Endothelial cell nucleus
Alveolar
epithelium
Fused basement
membranes of the
alveolar epithelium
and the capillary
endothelium
Respiratory
membrane
Red blood cell
in capillary
Alveoli (gas-filled
air spaces)
Type II (surfactant-
secreting) cell
Capillary
endothelium
Type II cells also secrete antimicrobial proteins
External respiration: O2 and CO2 flow easily down their concentration gradients, into and out of alveoli across thin, simple squamous epithelium
Figure 22.9c

23. 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

24. 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

25. 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

26. 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
pressure 760 mm Hg
(Relative to Patm= 0 mm Hg)
756
760
Transpulmonary
pressure
760 mm Hg
–756 mm Hg
= 4 mm Hg
Lung
Diaphragm
Figure 22.12

27. 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

28. 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

29. posterior and superior-
Inspiration: An Active Process
Changes in anterior-
posterior and superior-
inferior dimensions
Changes in lateral
dimensions
(superior view)
Sequence of events
Inspiratory muscles
contract (diaphragm
descends; rib cage rises). 1
Ribs are elevated
and sternum flares
as external
intercostals
contract.
Thoracic cavity volume
increases. 2
Lungs are stretched;
intrapulmonary volume
increases. 3
External
intercostals
contract.
Intrapulmonary pressure
drops below Patm (–1 mm Hg). 4
Air (gases) flows into
lungs down its pressure
gradient until intrapulmonary
pressure is 0 (equal to
atmospheric pressure). 5
Diaphragm
moves inferiorly
during contraction.
Figure 22.13
(1 of 2)

30. posterior and superior-
Expiration: Normally a Passive Process
Changes in anterior-
posterior and superior-
inferior dimensions
Changes in
lateral dimensions
(superior view)
Sequence
of events
Inspiratory muscles
relax (diaphragm rises; rib
cage descends due to
recoil of costal cartilages). 1
Ribs and sternum
are depressed
as external
intercostals
relax.
Thoracic cavity volume
decreases. 2
Elastic lungs recoil
passively; intrapulmonary
volume decreases. 3
External
intercostals
relax.
Intrapulmonary pressure
rises above Patm (+1 mm Hg). 4
Diaphragm
moves
superiorly
as it relaxes.
Air (gases) flows out of
lungs down its pressure
gradient until intra-
pulmonary pressure is 0. 5
Pressure anim. I online
Forced expiration is an active process: it uses abdominal and internal intercostal muscles
Pressure anim II online
Figure (2 of 2)

31. Atelectasis Atelectasis (lung collapse)
Plugged bronchioles  collapse of alveoli
Wound that admits air into pleural cavity (pneumothorax)

32. 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

33. Physical Factors Influencing Pulmonary Ventilation
Three factors that must be overcome by inspiratory muscles
Airway resistance (friction, usually insignificant if bronchioles wide open, increasing with smaller diameters)
Alveolar surface tension (alleviated by Type II alveolar cell surfactant)
Lung compliance: the change in lung volume that occurs with a given change in transpulmonary pressure (lung “stretchiness”)

34. 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

35. 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

36. 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