🌬️

Understanding Human Gas Exchange Processes

May 20, 2025

Summary Notes: Gas Exchange in Humans

Human Respiratory System

Key Structures

  • Lungs: Main organs for gas exchange.
  • Ribs and Intercostal Muscles: Protect lungs and heart; aid in breathing by expanding/contracting the rib cage.
  • Larynx: Contains vocal cords.
  • Trachea: Connects throat to bronchi; supported by C-shaped cartilage rings.
  • Bronchi: Carries air from trachea to lungs; branches into left and right lungs.
  • Bronchioles: Smaller branches from bronchi leading to alveoli.
  • Alveoli: Site of gas exchange; oxygen diffuses into blood, carbon dioxide diffuses out.

Ventilation

  • Breathing In:
    • Internal intercostal muscles relax; external muscles contract.
    • Ribs move up and out; diaphragm flattens.
    • Thorax volume increases, causing air to diffuse into lungs.
  • Breathing Out:
    • Thorax volume decreases, increasing pressure to push air out.
    • Generally passive, but can involve muscle contraction when forced.

Composition of Air

  • Inhaled air: Higher oxygen content.
  • Exhaled air: More carbon dioxide and water vapor.

Impact of Exercise

  • Increases rate of respiration and demand for oxygen.
  • Produces more carbon dioxide, prompting faster breathing and heart rate.

Adaptations of Exchange Surfaces

  • Large Surface Area: Facilitates efficient diffusion.
  • Thin Surface: Short diffusion distance for rapid exchange.
  • Good Blood Supply: Maintains concentration gradient.
  • Good Ventilation: Ensures efficient gas exchange.
  • Moisture: Allows gases to dissolve and diffuse effectively.

Protection from Pathogens

  • Goblet Cells: Secrete mucus to trap pathogens.
  • Cilia: Move mucus towards throat.
  • Stomach Acid: Destroys swallowed pathogens.