NSG 530 Module 5: Respiratory System

Jun 25, 2024

Respiratory System Lecture Notes

Main Functions of the Lungs

  • Gas exchange: Bringing in oxygen and expelling carbon dioxide.
  • Inhalation: Diaphragm contracts downward and chest muscles expand chest cavity, sucking in air.
  • Exhalation: Diaphragm and chest muscles relax, expelling air.

Pathway of Air

  1. Nasal Cavity
    • Air enters through nostrils.
    • Lined with mucus-producing cells (contain lysozymes) to trap dust, pollen, and bacteria.
    • Nose hairs trap particles forming boogers.
  2. Paranasal Sinuses
    • Air-filled spaces (frontal, ethmoid, sphenoid, maxillary sinuses).
    • Warm and moisten air, amplify voice.
  3. Pharynx (Throat)
    • Nasopharynx connects nasal cavity.
    • Oropharynx connects oral cavity.
    • Laryngopharynx connects to larynx.
    • Soft palate and uvula prevent food from entering nasopharynx.
  4. Larynx (Voice Box)
    • Epiglottis seals airway during swallowing.
    • Triggers cough reflex if foreign particles enter.
  5. Trachea (Windpipe)
    • Splits into two mainstem bronchi.
    • Right lung has 3 lobes; left lung has 2 lobes.
    • Right mainstem bronchus more vertical and wider.
  6. Bronchi and Bronchioles
    • Trachea supported by cartilage rings.
    • Smooth muscle innervated by autonomic nervous system.
      • Sympathetic nerves: Dilate airways via beta-2 adrenergic receptors.
      • Parasympathetic nerves: Constrict airways via muscarinic receptors.
    • Lined with ciliated columnar cells and goblet cells (mucus).
    • Mucociliary escalator moves mucus and particles up to pharynx.
    • Conducting bronchioles lead to respiratory bronchioles.
    • Terminal bronchioles mark end of conducting bronchioles.

Alveoli and Gas Exchange

  • Alveoli (around 500 million)
    • Tiny outpouchings in respiratory bronchioles.
    • Transition into alveolar ducts.
    • Lined by pneumocytes (thin epithelial cells).
    • Type I Pneumocytes: Main structural cells.
    • Type II Pneumocytes: Secrete surfactant, can transform into Type I.
  • Blood-Gas Barrier
    • Alveolar wall, basement membrane, and capillary wall facilitate gas exchange.
    • Carbon dioxide diffuses from blood to alveoli to be exhaled.
    • Oxygen diffuses from alveoli to blood to be distributed throughout the body.
  • Alveolar Macrophages
    • Capture particles, ride mucociliary escalator to pharynx.

Summary

  • Respiratory system: Facilitates gas exchange.
    • Pathway: Nostril -> Nasal cavity -> Pharynx -> Larynx -> Trachea -> Bronchi -> Conducting bronchioles -> Respiratory bronchioles -> Alveoli -> Capillary.
    • Oxygen inhaled, carbon dioxide exhaled.