Respiratory System
Chapter 22
Biology 2122
Respiratory System Functions
1. Pulmonary Ventilation
2. External Respiration
3. Respiratory Gas
4. Internal Respiration
Functional Zones
1. Respiratory
2. Conducting
Animation
Nose and Para-nasal Sinuses
Functions:
 Airway
 Warmth and moisture
 Filter and cleaning
 Resonation – speech
 Site of olfactory organs
 External nose
 Internal nose
○ Lined with olfactory mucosa
○ Mucus contains lysozyme (antibacterial)
○ Epithelial cells secrete defensins (natural antibiotic)
Conchae
Paranasal sinuses
Pharaynx
Nasopharynx
Oropharynx
Laryngopharynx
Nasal
Cavity
From the 4th to the 6th vertebrae
 attached to hyoid bone (superiorly)
Functions:
Opens airway
Route air and food into correct passageways
Voice production
Structure
9 cartilage (hyaline) rings
Thyroid cartilage fuses (two plates) and forms the laryngeal prominence (adam’s apple)
Arytenoid (anchors vocal cords), cuneiform and corniculate cartilages
Larynx
Larynx
• Ninth cartilage - epiglottis (elastic cartilage)
• Vocal folds (true vocal cords) contain no BVs so appear white;
vibrate and produce sound
– vestibular folds (false vocal cords)
– glottis
• Superior part of the larynx
– stratified squamous: protection from food
Trachea
4 inches (10-12 cm) long and 1
inch (2.5 cm) in diameter
Contains:
(1). Mucosa (goblet cells and P.S.
epithelium)
(2). Submucosa (CT)
(3). Adventitia (CT reinforced by 1620 Cartilage rings –hyaline
cartilage)
Final cartilage is larger - Carina
Trachea branches at the T-7 level
Right bronchi is wider, shorter
and more vertical
Bronchi branch into secondary
and tertiary bronchi
When the size becomes less than
1 mm in diameter - bronchiole
Terminal bronchioles - less than
0.5 mm in diameter
Bronchi and
Bronchial Tree
Respiratory Zone Structures
1. Terminal bronchioles ----- respiratory
bronchioles ---- alveoli
2. Alveolar ducts lead into the alveolar sacs
(terminal); gas exchange
3. 300 million alveoli
Alveoli wall contain
– Type-I cells (simple squamous)
– Type-II-secrete fluid
The alveolar and capillary walls
form the respiratory membrane
(air-blood barrier)
Other features of the alveoli:
– Pores between alveoli allow for
equalized air pressure
– Contain macrophages
Respiratory
Membrane
Lungs
Suspended in pleural cavity
connected to mediastinum by
vascular and bronchial
attachments called roots.
Costal surface of lungs lie in
contact with ribs
Hilus
Left lung is smaller - the cardiac
notch accommodates the heart
Fissures
Lung ‘odds and ends’
Each lobe of lung contains pyramid-shaped
bronchopulmonary segments separated by CT septa
– Each is served by own artery and vein
Lobules are smallest segments of lungs
– Each is served by a large bronchiole and branches
Lungs also contain elastic CT
– spongy and elastic
Lung Circulation
Pulmonary and bronchial circulation
Pulmonary arteries
• bring in blood to be oxygenated
• feed into the pulmonary capillary networks surrounded
by the alveoli
Fresh oxygenated blood - returned to the heart via the
pulmonary veins
Innervation - Lungs
Parasympathetic, Sympathetic motor fibers and
visceral sensory fibers enter the lungs via the
pulmonary plexus on the lung root
Parasympathetic fibers constrict air tubes
Sympathetic fibers dilate air tubes
Ventilation
 Inspiration (air into the
lungs)
 Expiration (out of the lungs)
Respiratory pressures - atm
pressure
Atmospheric Pressure (Patm)
 760 mmHg sea level=1 atm
 Pressure exerted by gases
surrounding the body
 Any pressure less than 760
mmHg is less than
atmospheric pressure
Mechanics of Breathing
Thoracic Cavity Pressure
Intrapulmonary Pressure (Ppul)
(a). Pressure in the alveoli
(b). May rise or fall (short periods) but always equalizes out to equal Patm
Intrapleural Pressure (Pip)
(a). Pressure in the pleural cavity fluctuates with breathing
(b). 4 mmHg Less than Ppul and Patm (negative pressure)
How is the Intrapleural pressure established?
Forces that pull lungs away from wall (cause collapse)
Force 1: Lungs Recoil
Force 2: Surface Tension of Alevolar Fluid
What opposes these forces?
Thoracic Cavity Pressure
1. Which force will win? Neither! Due to the
adhesive force between the parietal and
visceral pleura
2. What is the significance?
 Pressure differences inside and out side the lungs allow
for breathing to take place
 Air will move down the pressure concentration gradient
 Pressure is greater outside so air will move into the lungs
3. Consequences of a collapsed lung!
The Breathing Process- Ventilation
 1. Inspiration
 Enlargement of the thorax increases volume
 Boyle’s Law
 Greater the volume - number of gas particles per
unit volume decrease
 Pressure is greater outside of the lungs!
 2. Expiration
 Volume of thorax decreases pressure increases
 1 mm Hg higher than outer pressure
 Breathe out
Changes in Thoracic Volume
Pressure Changes and Resistance
Factors that Influence Pulmonary Ventilation
(1). Airway Resistance (non elastic source of
resistance)
 Drag decreases gas flow
 Upper respiratory tract is larger; midsize bronchi offer most
resistance; terminal bronchioles air flow basically stops
(2). Aveolar Surface Tension
 Liquids drawn together create surface tension
 Water: strong surface tension
 If left alone, water create ST on the alveoli and would collapse
the alveoli
 Production of surfactant
 Less force needed to overcome forces needed to expand lungs
Factors that Influence Pulmonary Ventilation
3. Lungs stretch due to elastic fibers- Lung Compliance
– (a). Expansion of lungs increases compliance
– (b). Determined by
• Distensibility of lung tissue
• Alveolar surface tension (must be kept low)
4. Diminished by
– (a). Fibrosis, scar tissue
– (b). Blockages
– (c). Reduced production of surfactants
– (d). Reduced flexibility of rib cage
Respiratory Volumes
Links for Ventilation
• Ventilation