Respiratory System Flashcards

Respiratory Sytem

• Essential Functions

  • Breathing

  • Gas Exchange: Essential for respiration; lack of oxygenated blood is fatal in ~5 minutes.

• Additional Functions:

  • Warming and filtration of inspired air

  • Communication

  • Acid and base balancing

  • Changing of intrabdominal pressure

  • Removal of waste products

  • Olfaction (sense of smell).

Structure of the Ventilatory System

• Divisions:

  1. Conducting Zone:

  • Components: Trachea, terminal bronchioles.

  1. Transitional and Respiratory Zones:

  • Components: Respiratory bronchioles, alveolar ducts, alveoli.

  • Function: Location of gas exchange for respiration, occupying 2.5 – 3.0 liters of total lung volume.

Lung Capacity Comparisons

• Total Lung Capacity:

  • Horse: ~55 liters (14.5 gallons!)

  • Humans: 5-6 liters (1.5 gallons)

  • Resting Tidal Volume:

  • Horse: ~5 liters

  • Human: ~0.5 liters

  • Average Breathing Rate: Humans: 12-16 breaths/minute.

Gas Exchange Process

• Pulmonary Ventilation: Ambient air moves into lungs, exchanges gases.

  • Inspired air adjusts to body temp, is filtered, & humidified via trachea.

  • Bronchial Division:

  • Bronchi further divide into bronchioles that lead to alveolar ducts.

• Alveolar Function: Alveoli are terminal branches providing maximal gas exchange surface area.

• Gas Movement: Air flows through trachea into terminal bronchi; slows upon reaching smaller passages.

Characteristics of the Lungs

• Average Weight: 1 kg

• Average Volume: 4-6 L

• Surface Area: Ranges from 50-100 m², significantly larger than body surface area.

• Alveoli Count: 300-800 million, involved in gas exchange with a major blood supply.

• Capillary-Alveoli Interaction: Allows O₂ to move into blood and CO₂ to diffuse out.

Mechanism of Breathing

• Volume Changes: Altered by expanding or decreasing thoracic cavity volume using muscles.

• Inspiration:

  • Muscles raise ribs, diaphragm contracts, increasing thoracic volume and decreasing pressure.

  • Abdominal engagement aids further airflow.

• Expiration:

  • At rest: diaphragm returns to position, lowering thoracic volume.

  • During exertion, intercostals and abdominal muscles contract to further decrease volume.

Gas Diffusion Laws

• Key Laws:

  1. Dalton’s Law: Total pressure = sum of individual gas pressures.

  • Allows calculation of individual gas pressures from total pressure.

  1. Henry’s Law: Gas dissolves in liquid in proportion to partial pressure and temperature.

  2. Fick’s Law: Rate of gas diffusion across alveoli is proportional to surface area and pressure difference; diffusion constant (D) is influenced by gas solubility and inversely by molecular weight.

Alveolar Gas Exchange Example

• At rest: Approx. 250 mL O₂ enters blood while 200 mL CO₂ exits.

• Gas Concentration & Pressure:

  • Atmospheric air composition: 20.9% O₂, 78% N₂, 0.03% CO₂.

Pulmonary Parameters

• Identifying Lung Volumes:

  • Tidal Volume (TV): volume of air per breath (600 mL)

  • Inspiratory Reserve Volume (IRV): maximal inhalation (3.0 L)

  • Expiratory Reserve Volume (ERV): forceful exhalation post-breath (1.2 L)

  • Residual Volume (RV): air remaining post-max exhalation (1.2 L)

  • Functional Residual Capacity (FRC) = ERV + RV (2.5 L).

  • Vital Capacity (VC) = TV + IRV + ERV (4.8 L total capacity).

Diagnosing COPD and Testing Parameters

• COPD Testing:

  • Airflow limitation measurements include FEV1/VC ratio, with <0.70 indicative of COPD.

• Comparing Performance in Different Sports:

  • Studies show variations in VC and airflow between athletes and control groups.