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Anatomy and Physiology of Respiration

Apr 21, 2025

Lecture Notes: Anatomy and Physiology of Respiration

Part 1: Anatomy of Respiration

Vocabulary and Definitions

Structural Areas

  • Pleura: Double-layered membrane surrounding the lungs that reduces friction.
  • Lobes: Sections of the lungs (Right lung: 3 lobes, Left lung: 2 lobes).
  • Upper Respiratory Tract: Consists of the nose, nasal cavity, pharynx, and larynx.
  • Lower Respiratory Tract: Includes the trachea, bronchi, bronchioles, and alveoli.

Muscles

  • Diaphragm: Dome-shaped muscle under the lungs; contracts during inhalation.
  • External Intercostals: Muscles between the ribs that expand the chest during breathing.

Pathway Structures

  • Nostrils: External openings for air intake.
  • Nasal Cavity: Warms, moistens, and filters air.
  • Oral Cavity: Secondary entrance for air.
  • Pharynx: Throat; common pathway for air and food.
    • Nasopharynx: Upper section behind nasal cavity.
    • Oropharynx: Middle section behind oral cavity.
    • Laryngopharynx: Lower section leading to the larynx.
    • Epiglottis: Flap that prevents food from entering the airway.
    • Larynx: Voice box; contains vocal cords.
    • Trachea: Windpipe; conducts air to bronchi.
    • Pseudostratified Epithelium: Ciliated cells lining airways for cleaning.
    • Cilia: Hair-like structures that move mucus and debris.
    • Mucus: Traps particles and pathogens.

Airway Branching

  • Left and Right (Primary) Bronchi: First branches off the trachea into each lung.
  • Secondary Bronchi: Branches to each lobe of the lung.
  • Tertiary Bronchi: Further division within the lobes.
  • Bronchioles: Smaller air passages without cartilage.
  • Terminal Bronchiole: Last part before alveoli.
  • Alveolar Duct: Leads from bronchioles to alveoli.
  • Alveoli: Air sacs where gas exchange occurs.

Learning Target: Compare Upper vs. Lower Respiratory Tracts

T-Chart Example

  • Upper Respiratory Tract

    • Nose, Nasal Cavity, Pharynx, Larynx
    • Filters, warms, and moistens air
    • Involved in smell and vocalization
    • Contains tonsils and epiglottis
  • Lower Respiratory Tract

    • Trachea, Bronchi, Bronchioles, Alveoli
    • Conducts air to lungs, gas exchange
    • Includes respiratory membrane
    • Includes alveolar sacs for gas exchange

Part 2: Physiology of Respiration

Vocabulary and Definitions

Processes

  • Pulmonary Ventilation: Movement of air into/out of lungs (breathing).
  • Respiratory Gas Transport: Transport of O₂ and CO₂ via bloodstream.
  • Inspiration: Breathing in; diaphragm contracts, volume increases.
  • Expiration: Breathing out; diaphragm relaxes, volume decreases.
  • Internal Respiration: Gas exchange between blood and body tissues.
  • External Respiration: Gas exchange between alveoli and blood.

Volumes & Capacities

  • Tidal Volume (TV): Air moved in/out during normal breathing (~500 mL).
  • Inspiratory Reserve Volume (IRV): Extra air inhaled after normal breath (~3100 mL).
  • Expiratory Reserve Volume (ERV): Extra air exhaled after normal breath (~1200 mL).
  • Residual Volume (RV): Air remaining after full exhalation (~1200 mL).
  • Vital Capacity (VC): Total air that can be exhaled after max inhalation (TV + IRV + ERV).
  • Total Lung Capacity (TLC): VC + RV (~6000 mL in adults).

Learning Target: Trajectory of an Oxygen Molecule

Pathway of Oxygen

  1. Enters through Nostrils/Nasal Cavity → filtered, warmed, humidified.
  2. Passes through Pharynx → Larynx → Trachea.
  3. Travels down Primary Bronchi → Secondary → Tertiary Bronchi.
  4. Enters Bronchioles → Terminal Bronchioles → Alveolar Ducts → Alveoli.
  5. Gas Exchange at alveoli → O₂ enters pulmonary capillaries.
  6. O₂ binds to hemoglobin in red blood cells.
  7. Blood transports O₂ via arteries → Body Tissues for Internal Respiration.

Lung Capacity in Action (Example)

  • If taking 12 breaths per minute with a Tidal Volume of 500 mL:
    • 12 x 500 mL = 6000 mL or 6 Liters per minute
    • During exercise, TV and breathing rate increase dramatically (up to ~100 L/min in elite athletes!)