BIOC33H3 Lecture Notes - Respiratory Center, Brainstem, Bronchus
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Chapter 26: Respiratory System
STRUCTURES AND FUNCTIONS
The primary purpose of the respiratory system is gas exchange, which involves the transfer of
oxygen and carbon dioxide between the atmosphere and the blood.
The upper respiratory tract includes the nose, pharynx, adenoids, tonsils, epiglottis, larynx, and
The lower respiratory tract consists of the bronchi, bronchioles, alveolar ducts, and alveoli.
In adults, a normal tidal volume (VT), or volume of air exchanged with each breath, is about 500
Ventilation involves inspiration (movement of air into the lungs) and expiration (movement of
air out of the lungs).
ABGs are measured to determine oxygenation status and acid-base balance. ABG analysis
includes measurement of the PaO2, PaCO2, acidity (pH), and bicarbonate (HCO3
–) in arterial
Arterial oxygen saturation can be monitored continuously using a pulse oximetry probe on the
finger, toe, ear, or bridge of the nose.
The respiratory center in the brainstem medulla responds to chemical and mechanical signals
from the body.
A chemoreceptor is a receptor that responds to a change in the chemical composition (PaCO2
and pH) of the fluid around it.
Mechanical receptors are stimulated by a variety of physiologic factors, such as irritants, muscle
stretching, and alveolar wall distortion.
The respiratory defense mechanisms include filtration of air, the mucociliary clearance system,
the cough reflex, reflex bronchoconstriction, and alveolar macrophages.
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