Anatomy Notes- 02/02/26

Introduction to Lung Volumes and Capacities

  • Lung volumes and capacities are critical to understanding respiration.

  • Volumes are measured in cubic centimeters.

  • Capacities represent optimum or maximum volumes of air that lungs can hold.

Lung Volumes

Definition and Explanation

  • Volume: Refers to the space inside the lungs, measured in cubic centimeters.

  • Capacity: The optimal or maximum amount of air that can fit in these volumes.

Key Lung Volumes

  1. Tidal Volume (TV)

    • Definition: The amount of air inhaled or exhaled during normal, relaxed breathing.

    • Typical Value: Approximately 500 cc in average adults.

    • Example: At rest, when sitting, TV is simply the regular breath taken without any force.

  2. Inspiratory Reserve Volume (IRV)

    • Definition: The additional air that can be inhaled after a normal inhalation, representing a deep breath.

    • Example: Used during activities like playing wind instruments or physical exertion.

    • In daily life, usually not reached during casual breathing.

  3. Expiratory Reserve Volume (ERV)

    • Definition: The additional air that can be forcefully exhaled after normal expiration.

    • Example: As seen during a spirometry test, where a patient exhales fully as instructed.

  4. Residual Volume (RV)

    • Definition: The air remaining in the lungs after a forceful expiration, ensuring that the lungs do not collapse.

    • Important for gas exchange during respiration, as it prevents total lung collapse.

Summary of Key Volumes

  • Tidal Volume (TV): Normal breath.

  • Inspiratory Reserve Volume (IRV): Deep inhalation.

  • Expiratory Reserve Volume (ERV): Forceful exhalation.

  • Residual Volume (RV): Air remaining post-exhalation.

Lung Capacities

Definition and Importance

  • Lung capacities are functional combinations of different lung volumes.

  • Understanding these capacities is vital for various fields including speech pathology.

Key Lung Capacities

  1. Inspiratory Capacity (IC)

    • Formula: IC = TV + IRV

    • Definition: Maximum amount of air that can be inhaled after normal expiration.

    • Average Value: Approximately 3,000 cc.

  2. Vital Capacity (VC)

    • Formula: VC = TV + IRV + ERV

    • Definition: Total amount of air that can be exhaled after taking the deepest breath possible.

    • Typical Value: Around 4,000 cc.

  3. Total Lung Capacity (TLC)

    • Formula: TLC = TV + IRV + ERV + RV

    • Definition: Total volume of air the lungs can hold, including residual volume.

    • Average Value: Approximately 5,100 cc, but can vary by age, sex, and physical condition.

Importance of Lung Capacities

  • Relevant for speech pathologists to assess and understand voice production and breathing patterns.

  • Vital for managing voice clients, and ensuring effective breath support for speaking and singing.

Postures and Their Effects on Vital Capacity

  • Seated Upright: Optimal for maximum lung function and inhalation.

  • Reclining: May reduce vital capacity by 20% due to gravity influencing diaphragm function.

  • Supine Position: Also decreases lung capacity, as forces act more on muscles of respiration.

Lung Pressure Concepts

Types of Pressure in Respiration

  1. Pulmonary (Alveolar) Pressure

    • Definition: Pressure within the alveoli of the lungs, specifically during breathing.

    • Important for understanding airflow during inhalation and exhalation.

  2. Intrapleural Pressure

    • Definition: Pressure within the pleural cavity, the space between the lungs and chest wall.

    • Typically negative, helping keep the lungs inflated.

  3. Subglottal Pressure

    • Definition: Pressure beneath the vocal folds; crucial for voice production.

    • Created when the vocal folds are closed and air from the lungs builds up.

    • Essential for speech pathologists to assess voice quality and loudness.

  4. Intraoral Pressure

    • Definition: The pressure within the oral cavity.

    • Varies during speech, affecting articulation and sound production.

  5. Atmospheric Pressure

    • Definition: The pressure exerted by the weight of air in the environment.

    • Acts as the baseline pressure affecting respiratory airflow.

Pressure Relationships During Breathing

  • At rest: Atmospheric, intraoral, alveolar pressures equalize.

  • During inhalation: Intrapleural pressure becomes more negative; alveolar pressure becomes lower than atmospheric, creating airflow into the lungs.

  • During exhalation: Alveolar pressure becomes positive, forcing air out, while intrapleural pressure remains negative but less so.

Summary of Airflow and Pressures

  • It is crucial to recognize how various pressures interact during the respiratory cycle.

  • Inhalation involves negative pressure that allows air to enter the lungs.

  • Exhalation changes these pressures, allowing air to exit the lungs efficiently.

Discussion of Relaxation Pressure

  • Relaxation Pressure: The pressure created by passive lung elasticity and thoracic wall recoil when relaxing from forced inhalation or exhalation.

  • Measured as a percentage of vital capacity; used to assess respiratory function.

Future Study and Applications

  • The dynamic nature of pressures and volumes in respiratory physiology highlights the importance of the respiratory system in both general health and specific applications like speech therapy.

  • Encouragement to discuss further questions during office hours or next class.