Mechanisms of Ventilation
Learning Targets: Define the process of ventilation. (knowledge) Determine how certain factors affect breathing rate. (reasoning) Ventilation- movement of air into and out of lungs
1 2 3-4 Also refer to the next page Structures 3-4 Inhalation 5-9 Contraction of external intercostal muscles pulls ribs upward and outward. Diaphragm contracts. Volume of thoracic cavity increases. Pressure in pleural cavity decreases. Lungs inflate as air rushes in. 5-9 Image Inhalation (a) Maximum Inhalation (b)
10-11 Expiration (Exhalation)
12-15 Muscles of inhalation relax due to elastic recoil. Volume of thoracic cavity decreases. Pressure in pleural cavity increases. Lungs deflate. Exhalation (a) Maximum Exhalation (b)
16 Exhalation (a) Maximum Exhalation (b) Please watch by clicking on the illustration.
Summary animation for questions 5-16. Theres more to it Like a new balloon, a new lung has a lot of elastic recoil. It is difficult to inflate. The first breath for an infant is 20 times more difficult than any breath after that. Also, elastic recoil can also cause a balloon or alveoli to completely collapse.
Alveoli cannot completely collapse.It would take too much energy to breath. So the body produces surfactant which decrease elastic recoil. Premature babies may not produce surfactant and need to have it administer artificially. Surfactant A phospholipid Reduces elastic recoil
17-19 A phospholipid Reduces elastic recoil Prevents complete deflation of our lungs Measuring Breathing Intensities
A respiratory therapist uses a peek flow meter to measure the patients breathing intensities. Breathing intensities graph Selected volumes, capacities and levels
Tidal Volume (TV) Volume of air inspired/expired during rest breathing. Expiratory Reserve Volume (ERV) Volume of air that can be forcefully exhaled, below tidal volume. Inspiratory Reserve Volume (IRV) Volume of air that can be inhaled, above tidal volume. Vital Capacity (VC) Volume of air that can be inhaled/exhaled (i.e. VC=IRV +TV+ERV) Residual Volume (RV) Volume of air left after maximal expiration. Measurable, but not easily so. Total Lung Capacity (TLC) Volume of air enclosed in the respiratory system (i.e. TLC=RV+ERV+TV+IRV) Resting End Expiratory Level (REL) Location in lung volume space where tidal breathing typically ends (35-40 % VC in upright position) Some typical adult values
Typical Volumes & Capacities Vital Capacity (VC) 4-5 liters Total Lung Capacity (TLC) ~ one liter more than VC Resting Tidal Volume (TV) ~ 10 % VC Resting expiratory end level (REL) ~ 35-40% VC when upright Typical Rest Breathing Values Respiratory rate 12-15 breaths/minute Alveolar Pressure Palv +/- 2 cm H20 Airflow ~ 200 ml/sec How does breathing affect speech?