Lecture Notes: Respiratory Physiology

Overview of the Lungs

• Main Function: Gas exchange
  • Inhale: Oxygen is brought in.
  • Exhale: Carbon dioxide is expelled.
• Muscles Involved: Diaphragm and chest muscles contract/relax to facilitate breathing.

Pathway of Air Inhalation

1. Nasal Cavity
   • Air enters through nostrils.
   • Lined with mucus-releasing cells:
     • Mucus is salty, sticky, contains lysozymes (bacteria-killing enzymes).
     • Nose hairs trap large particles, forming boogers.
2. Paranasal Sinuses
   • Types: Frontal, Ethmoid, Sphenoid, Maxillary.
   • Functions: Warm/moisten air, amplify voice.
3. Pharynx
   • Regions: Nasopharynx, Oropharynx, Laryngopharynx.
   • Soft Palate and Uvula: Prevent food entry into nasopharynx during eating.
4. Larynx
   • Contains the epiglottis: Prevents food from entering airway.
   • Located before the trachea.

Lower Respiratory Tract

• Trachea: Windpipe leading to lungs.
• Bronchi
  • Main Stem Bronchi: Right bronchus is wider, more vertical.
  • Carina: Point of split between two bronchi.
• Lung Structure
  • Right Lung: 3 lobes (upper, middle, lower).
  • Left Lung: 2 lobes (upper, lower).

Bronchi and Bronchioles

• Airway Structure
  • Large bronchi supported by cartilage rings.
  • Contains smooth muscle with autonomic nervous system innervation.
    • Sympathetic: Stimulates dilation (fight/flight).
    • Parasympathetic: Stimulates constriction (rest/digest).
• Mucociliary Escalator
  • Lined with ciliated columnar cells and goblet cells.
  • Moves mucus and particles towards the pharynx.
• Conducting Bronchioles
  • Smaller airways without cartilage support.
  • Lined by ciliated cells, goblet cells, and club cells (secrete protective substances).

Respiratory Zone

• Respiratory Bronchioles
  • Contain alveoli outpouchings.
• Alveolar Ducts
  • Final destination of inhaled air.
• Alveoli
  • Lined by type 1 and type 2 pneumocytes.
    • Type 1: Regular pneumocytes.
    • Type 2: Secrete surfactant, can transform to type 1.
  • Surrounded by capillary walls for gas exchange.

Gas Exchange Mechanism

• Blood-Gas Barrier
  • Consists of alveolar wall, basement membrane, capillary wall.
• Diffusion
  • Oxygen diffuses into blood, carbon dioxide diffuses into alveoli.

Recap

• Respiratory system facilitates gas exchange by airway conduction.
• Key structures: Pharynx, larynx, trachea, bronchi, bronchioles, alveoli.
• Inhaled air delivers oxygen to tissues, and exhaled air removes carbon dioxide.

Additional Information

• Resources: Osmosis.org for further study tools.
• Acknowledgements: Thanks to viewers and contributors for support.