Respiratory System Structure and Function

Study Notes

The respiratory system is made up of conducting airways and respiratory airways.
Conducting airways transport air, while respiratory airways participate in gas exchange.
Conducting airways warm, filter, moisten, and remove foreign materials.
Nasal passages are the preferred route for air entry, filtering, warming, and humidifying it.
Mouth and pharynx serve as an alternate airway during nasal obstruction or when large volumes of air are required.
The larynx connects the oropharynx to the trachea, functioning in speech and protecting the lungs from foreign substances.
The tracheobronchial tree comprises the trachea, bronchi, and bronchioles.
Bronchospasm can narrow bronchioles, impairing airflow.

Respiratory airways are responsible for gas exchange.
They also inactivate vasoactive substances, convert angiotensin I to angiotensin II, and serve as a blood reservoir.
Lobules are the smallest functional units of the lungs, each containing a terminal bronchiole, arteriole, pulmonary capillaries, and venule.
Alveoli are the specific site of gas exchange.
Alveolar sacs are thin-walled, cup-shaped structures with thin septa. A capillary network occupies most of the septa.
An adult lung contains approximately 300 million alveoli, providing a large surface area for gas exchange.
Type I and Type II alveolar cells exist. Type II cells synthesize pulmonary surfactant.
Surfactant is a lipoprotein that reduces surface tension, allowing alveoli to remain open.
Alveolar macrophages are responsible for phagocytizing foreign particles and microorganisms.