Function of the lung: The primary function of the lung is gas exchange, involving the intake of
oxygen and elimination of carbon dioxide. It also plays a role in regulating blood pH, filtering
small clots and metabolizing various compounds
Structure of the lung: the lung is anatomically divided into two lobes, with the right lung
comprising three lobes and left two. It consists of airways(bronchi and bronchioles), alveolar
ducts and alveoli. The respiratory zone is where gas exchange occurs, primarily in the alveoli.
The lung also contains blood vessels, nerves and lymphatics
Atelectasis: collapse of lung tissue, resulting in reduced or absent gas exchange. Can occur
due to airway obstruction, lung compression or increased surface tension. It often lead to
ventilation perfusion mismatch.( can be caused by puncture, introduction of foreign body, for
young individual, swallowing small objects may cause this)
Acute lung injury/ Acute respiratory disease syndrome(ARDS): ARDS is a severe form of
acute lung injury characterized by diffuse alveolar damage, leading to rapid onset of respiratory
failure. It is caused by a variety of direct and indirect lung injuries leading to increased vascular
permeability, alveolar edema, and inflammation. This results in impaired gas exchange and
reduced lung compliance.( hardness on breathing, Covid, fungal infection, and radiation could
cause this)
Common forms of Emphysema:
● Centriacinar Emphysema: Primarily affects the central or proximal parts of the acinus
and is strongly associated with smoking
○ Gaps and holes, could see macrophages(brown chunky)
○ Macrophage very specific to smoking
○ Marijuana- holds breath, found on periphery of the lung
● Panacinar emphysema: Involves the entire acinus uniformly and is commonly seen in
alpha-1 antitrypsin deficiency
○ Genetic syndrome, impacts all aspect of lung
● Distal Acinar Emphysema: Predominantly involves the distal part of the acinus and is
associated with spontaneous pneumothorax in young adults
Hypersensitivity Reaction in Asthma: involves a Type 1 hypersensitivity reaction (involves
eosinophils, decreased histamine, hyperactive airway), where exposure to allergens trigger the
production of IgE antibodies. These antibodies sensitize mast cells, leading to degranulation
and release of mediators like histamine, causing bronchoconstriction, inflammation, and airway
hyperresponsiveness(could see change in mucus cell in histology slide)
Morphologic Changes in Asthma: Asthmatic airways exhibits epithelial shedding, goblet cell,
hyperplasia, basement membrane thickening, subepithelial fibrosis, increased smooth muscle
mass, and infiltration by inflammatory cells such as eosinophils.
Granulomatous Lung Disease: It is characterized by the formation of granulomas, which are
nodular inflammatory lesions. Etiologies include infection (ex. Tuberculosis, fungal infections),
autoimmune diseases(ex. sarcoidosis), and exposure to certain inhaled environmental agents(
infection, fungal disease, flammable disease)
oxygen and elimination of carbon dioxide. It also plays a role in regulating blood pH, filtering
small clots and metabolizing various compounds
Structure of the lung: the lung is anatomically divided into two lobes, with the right lung
comprising three lobes and left two. It consists of airways(bronchi and bronchioles), alveolar
ducts and alveoli. The respiratory zone is where gas exchange occurs, primarily in the alveoli.
The lung also contains blood vessels, nerves and lymphatics
Atelectasis: collapse of lung tissue, resulting in reduced or absent gas exchange. Can occur
due to airway obstruction, lung compression or increased surface tension. It often lead to
ventilation perfusion mismatch.( can be caused by puncture, introduction of foreign body, for
young individual, swallowing small objects may cause this)
Acute lung injury/ Acute respiratory disease syndrome(ARDS): ARDS is a severe form of
acute lung injury characterized by diffuse alveolar damage, leading to rapid onset of respiratory
failure. It is caused by a variety of direct and indirect lung injuries leading to increased vascular
permeability, alveolar edema, and inflammation. This results in impaired gas exchange and
reduced lung compliance.( hardness on breathing, Covid, fungal infection, and radiation could
cause this)
Common forms of Emphysema:
● Centriacinar Emphysema: Primarily affects the central or proximal parts of the acinus
and is strongly associated with smoking
○ Gaps and holes, could see macrophages(brown chunky)
○ Macrophage very specific to smoking
○ Marijuana- holds breath, found on periphery of the lung
● Panacinar emphysema: Involves the entire acinus uniformly and is commonly seen in
alpha-1 antitrypsin deficiency
○ Genetic syndrome, impacts all aspect of lung
● Distal Acinar Emphysema: Predominantly involves the distal part of the acinus and is
associated with spontaneous pneumothorax in young adults
Hypersensitivity Reaction in Asthma: involves a Type 1 hypersensitivity reaction (involves
eosinophils, decreased histamine, hyperactive airway), where exposure to allergens trigger the
production of IgE antibodies. These antibodies sensitize mast cells, leading to degranulation
and release of mediators like histamine, causing bronchoconstriction, inflammation, and airway
hyperresponsiveness(could see change in mucus cell in histology slide)
Morphologic Changes in Asthma: Asthmatic airways exhibits epithelial shedding, goblet cell,
hyperplasia, basement membrane thickening, subepithelial fibrosis, increased smooth muscle
mass, and infiltration by inflammatory cells such as eosinophils.
Granulomatous Lung Disease: It is characterized by the formation of granulomas, which are
nodular inflammatory lesions. Etiologies include infection (ex. Tuberculosis, fungal infections),
autoimmune diseases(ex. sarcoidosis), and exposure to certain inhaled environmental agents(
infection, fungal disease, flammable disease)
