Anatomy of the Respiratory System
The respiratory system is responsible for gas exchange — supplying oxygen to the body and removing carbon dioxide. It is divided into two main parts:
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🔹 1. Upper Respiratory Tract
Includes structures outside the chest cavity:
a) Nose and Nasal Cavity
Filters, warms, and moistens incoming air.
Contains hair and mucus to trap dust and pathogens.
b) Pharynx (Throat)
Shared by respiratory and digestive systems.
Divided into:
Nasopharynx
Oropharynx
Laryngopharynx
c) Larynx (Voice Box)
Located below the pharynx.
Contains vocal cords.
Epiglottis prevents food from entering the airway.
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🔹 2. Lower Respiratory Tract
Located within the chest cavity:
a) Trachea (Windpipe)
A tube supported by C-shaped cartilage rings.
Conducts air from larynx to bronchi.
b) Bronchi and Bronchioles
Trachea divides into:
Right and left primary bronchi → enter lungs.
Bronchi → secondary → tertiary bronchi → bronchioles.
Bronchioles are smaller airways ending in alveoli.
c) Lungs
Two lungs: Right (3 lobes), Left (2 lobes).
Covered by pleura (double-layered membrane).
Contains alveoli — tiny air sacs for gas exchange.
d) Alveoli
Functional unit of the lungs.
Surrounded by capillaries.
Site of oxygen and carbon dioxide exchange.
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🔹 3. Supporting Structures
a) Diaphragm
Dome-shaped muscle below the lungs.
Contracts during inhalation → air enters lungs.
b) Intercostal Muscles
Located between ribs.
Help expand and shrink chest cavity.
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📌 Summary Diagram (Text-based)
Nose → Pharynx → Larynx → Trachea → Bronchi → Bronchioles → Alveoli
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📘 Extra Notes for Pharmacy Students:
Airways are lined with mucociliary epithelium (important in drug absorption and defense).
Surfactant (produced in alveoli) reduces surface tension — crucial for breathing.
Many inhalation drugs target bronchioles and alveoli (e.g., bronchodilators, corticosteroids).
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