BIOD 331 Module 5 Pathophysiology
(Disorders of the Pulmonary System, Mechanisms of Breathing, Ventilation and Perfusion,
Pulmonary Disorders-COPD & Asthma, Pulmonary Disorders-Pneumothorax & Atelectasis,
Pulmonary Disorders-Pulmonary Embolism, ARDS, Respiratory Acidosis)
Module 5: Disorders of the Pulmonary System
5.1: Physiology Review
● Main function of respiratory system is gas exchange. Primary goal is to get oxygen
into the blood while expelling CO2 from the body
● Divided into conducting airways and respiratory tissues. Nasal passages, mouth and
pharynx, larynx, trachea, bronchi, bronchioles are conducting airways. Air brought
in from atm & directed to lungs through conducting airways, gas exchange takes
place in resp tissues in lungs
● Most conducting airways are lined w ciliated pseudostratified columnar epithelium.
Ciliated cells protect airway by entrapping particles and redirecting them back
toward oropharynx where they can be expectorate or swallowed. Within ciliated
cells, mucus-secreting glands secrete antibacterial enzymes. Bronchus contains
smooth muscle cells, mucus glands, connective tissue, and cartilage
● Smaller bronchioles are made of simple epithelium, lack cartilage, wall is thinner.
Alveolar wall made for gas exchange not structural support
● Tracheobronchila tree starts at conducting airway and branches into lobes of the
lungs, ending in the respiratory airway where gas exchange takes place. Trachea,
bronchi, bronchioles
● Trachea connects larynx to bronchi, contains C shaped rings of hyaline cartilage to
prevent collapse. At base, divides to form L and R primary bronchi. Each main
bronchus contains pulmonary arteries, veins, and lymph vessels, enter the lung
through the hilum. Between main bronchi is the carina (ridge), highly sensitive
tissue that initiates violent coughing when contacted by a foreign object (food)
● Main bronchi divide into secondary lobular bronchi, supplying each lobe of the lungs-
R has 3 lobes, L has 2 due to heart position. Secondary bronchi divide to form
segmental bronchi
● Segmental bronchi branch into smaller bronchi until they become terminal bronchi-
smallest structures in conducting airways. Bronchi initially composed primarily of
cartilage, gradually replaced by smooth muscle and elastic tissue, by the time
bronchi branch into bronchioles, no cartilage is present
, ● Conducting airway terminates at terminal bronchioles, respiratory airways begin at
respiratory bronchioles
● Airways increase in diameter and length throughout childhood. Number and size of
alveoli increase until adolescence when respiratory development fully matures
● Gas exchange occurs in resp bronchioles as well as alveolar ducts & sacs located in
lobules of lung. Deox blood enters lungs through pulmonary artery, ox blood exits
through pulm vein
● Alveoli are sites of gas exchanges between air & blood. Alveolus is sac that fills w
ox air when breathing in, allows air to pass across membrane into blood vessel
(alveolar capillary). Alveolus contracts back down to let CO2 out and begin cycle
again. Capillaries are abundant to allow blood & air to constantly mix. O2 from
alveoli diffuses into blood, CO2 from blood diffuses into alveoli. Alveolar epithelium
has type 1 & type 2 cells plus macrophages
● Type 1 alveolar cells are 95% of surface area, thin squamous cells. Cannot divide
● Type 2 alveolar cells are cuboidal, 5% of surface area. Synthesize surfactant which
decreases surface tension in alveoli & allows for greater ease in lung inflation. Upon
lung injury, type 2 cells proliferate into both type 1 and 2 cells. Macrophages
remove offending substances from alveoli
5.2: Mechanisms of Breathing
● Ventilation: mechanical process that uses pressure differences to move air in and
out of lungs. As gas (air) always moves from areas of greater pressure into areas of
lesser pressure, during inspiration resp muscles expand thoracic cavity which
lowers pressure inside lung relative to atm, causing air to flow into the lungs. During
expiration, the resp muscles relax, and as thoracic cavity retracts a greater
internal pressure relative to the outside atm is created causing the high pressure
air in the lung ot be expelled from the body towards the area outside the body of
lesser pressure
● Intrapulmonary pressure or alveolar pressure is measured pressure inside airways
and alveoli. When air is neither being inspired or expired, the intrapulmonary
pressure is equal to atmospheric pressure, or zero. The intrapleural pressure is
measured pressure in pleural cavity. In normal inflated lung, intrapleural pressure is
negative related intrapulmonary pressure. Negative pressure in pleural cavities.
Caused by oppositional pull that occurs between parietal and visceral layers of the
pleura. As elastic recoil of lungs increases, intrapleural pressure becomes more
negative during inspiration than expiration. Holds lungs against chest wall, without
, it the elastic recoil of lungs would cause them to collapse. The intrathoracic
pressure is in the thoracic cavity, equal to intrapleural pressure
● Lungs are contained in thoracic cavity with heart, great vessels, and esophagus.
Breathing depends on this closed cavity
● Diaphragm is main muscle of inspiration. When diaphragm contracts (inspiration),
the chest expands. In a minor role, external intercostal muscles, scalene, and
sternocleidomastoid muscles aid in breathing. Each is associated along ribs, raising
and spreading them during inhalation, most commonly exerting aid during exercise
or difficulty breathing
● Innervated primarily by C4 but also C3 and C5 of spinal cord. People who sustain
spinal cord injury above C3 lose diaphragm function and require mechanical
ventilation. Paralysis on one side of the diaphragm causes the chest to move up on
that side rather than down during inspiration because of the negative pressure in
the chest. This is referred to as paradoxical movement
● Lung compliance is the ease w which lungs can inflate. Takes more pressure to move
air into a noncompliant lung than a compliant one. Lung compliance depends on
multiple factors including overall water content and surface tension, as well as the
amount of elastin and collagen fibers that are present
● Surface tension refers to the force exerted by water molecules on the surface of
alveoli. As water molecules are held together by strong covalent bonds, this force
is stronger than the force holding air molecules within the alveolar space. Air leaves
during exhalation, strong surface tension the water exerts on the surrounding
tissue causes the alveoli to deflate. Excess surface tension causes water molecules
in liquid film to contract even stronger, making lung inflation less compliant. Body
also contains pulmonary surfactants which lower surface tension and makes lung
inflation easier
● Elastin fibers are easily stretched, making lung tissue more compliant or easier to
inflate. Collagen fibers resist stretching and decrease lung compliance. Elastic
recoil is the ability of the elastic fiber of the lung to return to their original
position after being stretched. With emphysema, the elastic components lose their
recoil, making lungs easy to inflate but difficult to deflate
● Lung volumes refer to the amount of air exchanged from a single event during
ventilation, either from inhaling or exhaling. Lung volumes can be categorized into
four main components, of which 3 can be directly measured using spirometer
○ Tidal volume (Vt) is normal volume of air inhaled or exhaled w each breath,
500 mL
(Disorders of the Pulmonary System, Mechanisms of Breathing, Ventilation and Perfusion,
Pulmonary Disorders-COPD & Asthma, Pulmonary Disorders-Pneumothorax & Atelectasis,
Pulmonary Disorders-Pulmonary Embolism, ARDS, Respiratory Acidosis)
Module 5: Disorders of the Pulmonary System
5.1: Physiology Review
● Main function of respiratory system is gas exchange. Primary goal is to get oxygen
into the blood while expelling CO2 from the body
● Divided into conducting airways and respiratory tissues. Nasal passages, mouth and
pharynx, larynx, trachea, bronchi, bronchioles are conducting airways. Air brought
in from atm & directed to lungs through conducting airways, gas exchange takes
place in resp tissues in lungs
● Most conducting airways are lined w ciliated pseudostratified columnar epithelium.
Ciliated cells protect airway by entrapping particles and redirecting them back
toward oropharynx where they can be expectorate or swallowed. Within ciliated
cells, mucus-secreting glands secrete antibacterial enzymes. Bronchus contains
smooth muscle cells, mucus glands, connective tissue, and cartilage
● Smaller bronchioles are made of simple epithelium, lack cartilage, wall is thinner.
Alveolar wall made for gas exchange not structural support
● Tracheobronchila tree starts at conducting airway and branches into lobes of the
lungs, ending in the respiratory airway where gas exchange takes place. Trachea,
bronchi, bronchioles
● Trachea connects larynx to bronchi, contains C shaped rings of hyaline cartilage to
prevent collapse. At base, divides to form L and R primary bronchi. Each main
bronchus contains pulmonary arteries, veins, and lymph vessels, enter the lung
through the hilum. Between main bronchi is the carina (ridge), highly sensitive
tissue that initiates violent coughing when contacted by a foreign object (food)
● Main bronchi divide into secondary lobular bronchi, supplying each lobe of the lungs-
R has 3 lobes, L has 2 due to heart position. Secondary bronchi divide to form
segmental bronchi
● Segmental bronchi branch into smaller bronchi until they become terminal bronchi-
smallest structures in conducting airways. Bronchi initially composed primarily of
cartilage, gradually replaced by smooth muscle and elastic tissue, by the time
bronchi branch into bronchioles, no cartilage is present
, ● Conducting airway terminates at terminal bronchioles, respiratory airways begin at
respiratory bronchioles
● Airways increase in diameter and length throughout childhood. Number and size of
alveoli increase until adolescence when respiratory development fully matures
● Gas exchange occurs in resp bronchioles as well as alveolar ducts & sacs located in
lobules of lung. Deox blood enters lungs through pulmonary artery, ox blood exits
through pulm vein
● Alveoli are sites of gas exchanges between air & blood. Alveolus is sac that fills w
ox air when breathing in, allows air to pass across membrane into blood vessel
(alveolar capillary). Alveolus contracts back down to let CO2 out and begin cycle
again. Capillaries are abundant to allow blood & air to constantly mix. O2 from
alveoli diffuses into blood, CO2 from blood diffuses into alveoli. Alveolar epithelium
has type 1 & type 2 cells plus macrophages
● Type 1 alveolar cells are 95% of surface area, thin squamous cells. Cannot divide
● Type 2 alveolar cells are cuboidal, 5% of surface area. Synthesize surfactant which
decreases surface tension in alveoli & allows for greater ease in lung inflation. Upon
lung injury, type 2 cells proliferate into both type 1 and 2 cells. Macrophages
remove offending substances from alveoli
5.2: Mechanisms of Breathing
● Ventilation: mechanical process that uses pressure differences to move air in and
out of lungs. As gas (air) always moves from areas of greater pressure into areas of
lesser pressure, during inspiration resp muscles expand thoracic cavity which
lowers pressure inside lung relative to atm, causing air to flow into the lungs. During
expiration, the resp muscles relax, and as thoracic cavity retracts a greater
internal pressure relative to the outside atm is created causing the high pressure
air in the lung ot be expelled from the body towards the area outside the body of
lesser pressure
● Intrapulmonary pressure or alveolar pressure is measured pressure inside airways
and alveoli. When air is neither being inspired or expired, the intrapulmonary
pressure is equal to atmospheric pressure, or zero. The intrapleural pressure is
measured pressure in pleural cavity. In normal inflated lung, intrapleural pressure is
negative related intrapulmonary pressure. Negative pressure in pleural cavities.
Caused by oppositional pull that occurs between parietal and visceral layers of the
pleura. As elastic recoil of lungs increases, intrapleural pressure becomes more
negative during inspiration than expiration. Holds lungs against chest wall, without
, it the elastic recoil of lungs would cause them to collapse. The intrathoracic
pressure is in the thoracic cavity, equal to intrapleural pressure
● Lungs are contained in thoracic cavity with heart, great vessels, and esophagus.
Breathing depends on this closed cavity
● Diaphragm is main muscle of inspiration. When diaphragm contracts (inspiration),
the chest expands. In a minor role, external intercostal muscles, scalene, and
sternocleidomastoid muscles aid in breathing. Each is associated along ribs, raising
and spreading them during inhalation, most commonly exerting aid during exercise
or difficulty breathing
● Innervated primarily by C4 but also C3 and C5 of spinal cord. People who sustain
spinal cord injury above C3 lose diaphragm function and require mechanical
ventilation. Paralysis on one side of the diaphragm causes the chest to move up on
that side rather than down during inspiration because of the negative pressure in
the chest. This is referred to as paradoxical movement
● Lung compliance is the ease w which lungs can inflate. Takes more pressure to move
air into a noncompliant lung than a compliant one. Lung compliance depends on
multiple factors including overall water content and surface tension, as well as the
amount of elastin and collagen fibers that are present
● Surface tension refers to the force exerted by water molecules on the surface of
alveoli. As water molecules are held together by strong covalent bonds, this force
is stronger than the force holding air molecules within the alveolar space. Air leaves
during exhalation, strong surface tension the water exerts on the surrounding
tissue causes the alveoli to deflate. Excess surface tension causes water molecules
in liquid film to contract even stronger, making lung inflation less compliant. Body
also contains pulmonary surfactants which lower surface tension and makes lung
inflation easier
● Elastin fibers are easily stretched, making lung tissue more compliant or easier to
inflate. Collagen fibers resist stretching and decrease lung compliance. Elastic
recoil is the ability of the elastic fiber of the lung to return to their original
position after being stretched. With emphysema, the elastic components lose their
recoil, making lungs easy to inflate but difficult to deflate
● Lung volumes refer to the amount of air exchanged from a single event during
ventilation, either from inhaling or exhaling. Lung volumes can be categorized into
four main components, of which 3 can be directly measured using spirometer
○ Tidal volume (Vt) is normal volume of air inhaled or exhaled w each breath,
500 mL
