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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 outof the lungs
External respiration: O2 and CO2
exchange between the lungsand the blood
Transport: O2 and CO2
in the blood
Internal respiration: O2 and CO2
exchange between systemic bloodvessels and tissues
Respiratorysystem
Circulatorysystem
Organs of the Respiratory systemKey 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
Figure 22.3c
Sphenoid sinus Frontal sinus
Nasal meatuses(superior, middle,and inferior)
Nasopharynx
Uvula
Palatine tonsilIsthmus of thefauces
Posterior nasalaperture
Opening ofpharyngotympanictube
Pharyngeal tonsil
Oropharynx
Laryngopharynx
Vocal fold
Esophagus
(c) Illustration
Nasal conchae(superior, middle and inferior)
Nasal vestibuleNostril
Nasal cavity
Hard palate
Soft palate
Tongue
Lingual tonsil
Epiglottis
Hyoid boneLarynx
Thyroid cartilageVestibular fold
Cricoid cartilage
Thyroid glandTrachea
Cribriform plateof ethmoid bone
Upper Respiratory Tract
Anatomy of the Nasal Cavity
hard palate soft palate
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
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
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
Figure 22.3b
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
Figure 22.6b
(b) Photomicrograph of the tracheal wall (320x)
Hyaline cartilage
• Lamina propria (connective tissue)Submucosa
Mucosa
Seromucous glandin submucosa
• Pseudostratified ciliated columnar epithelium
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, double-layered 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
Figure 22.9a
Elasticfibers
Smoothmuscle
Alveolus
Capillaries
Terminal bronchiole
Respiratory bronchiole
Capillaries Surround Alveoli to Pick Up O2 and Deliver CO2
Figure 22.8b
(b)
Alveolarpores
Alveolarduct
Respiratorybronchiole
Alveoli
Alveolarsac
Figure 22.9c
Capillary
Type II (surfactant-secreting) cell
Type I cellof alveolar wall
Endothelial cell nucleusMacrophage
Alveoli (gas-filledair spaces)
Red blood cellin capillary
Alveolar pore
Capillary endothelium
Fused basement membranes of the alveolar epitheliumand the capillary endothelium
Alveolar epithelium
Respiratorymembrane
Red blood cell
O2
AlveolusCO2
Capillary
Alveolus
Type II cells also secrete antimicrobial proteins
Alveolar Structure and Cellular Composition(The Respiratory Membrane)
Nucleus of type I(squamousepithelial) cell
External respiration: O2 and CO2 flow easily down their concentration gradients, into and out of alveoli across thin, simple squamous epithelium
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
Figure 22.12
Atmospheric pressure
Intrapleuralpressure756 mm Hg(–4 mm Hg)
Transpulmonarypressure760 mm Hg –756 mm Hg= 4 mm Hg
Thoracic wall
DiaphragmLung
Intrapulmonarypressure 760 mm Hg(Relative to Patm= 0 mm Hg)
Parietal pleura
Pleural cavityVisceral pleura
756
760
Lungs are Inflated if Transpulmonary Pressure > 0
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
Figure 22.13 (1 of 2)
Sequence of events
Changes in anterior-posterior and superior-
inferior dimensions
Changes in lateraldimensions
(superior view)
Ribs are elevatedand sternum flares
as externalintercostals
contract.
Diaphragmmoves inferiorly
during contraction.
Externalintercostalscontract.
Inspiratory muscles contract (diaphragm descends; rib cage rises).
2
1
Thoracic cavity volume increases.
3 Lungs are stretched; 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).
Inspiration: An Active Process
Figure 22.13 (2 of 2)
Sequenceof events
Changes in anterior-posterior and superior-
inferior dimensions
Changes inlateral dimensions
(superior view)
Ribs and sternumare depressed
as externalintercostals
relax.
Externalintercostalsrelax.
Diaphragmmovessuperiorlyas it relaxes.
1 Inspiratory muscles relax (diaphragm rises; rib cage descends due to recoil of costal cartilages).
2 Thoracic cavity volume decreases.
3 Elastic lungs recoil passively; intrapulmonary volume decreases.
4 Intrapulmonary pressurerises above Patm (+1 mm Hg).
5 Air (gases) flows out of lungs down its pressure gradient until intra-pulmonary pressure is 0.
Expiration: Normally a Passive Process
Forced expiration is an active process: it uses abdominal and internal intercostal muscles
Pressure anim. I online
Pressure anim II online
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
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”)
1. Airway resistance (friction, usually insignificant if bronchioles wide open, increasing with smaller diameters)
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