| What is the conducting zone in the respiratory system? | Conducting zone is the route for inhaled and exhaled air. It consists of the nose, pharynx, larynx, trachea, bronchi and bronchioles. It is involved in the warming and humidifying process and removes debris and pathogens (Celia – hair-like structures that collect debris). |
| What is the respiratory zone of the respiratory system? | The respiratory zone is directly involved with gas exchange, which requires the diffusion of oxygen and carbon dioxide between the alveoli and blood. It consists of the bronchioles, alveolar ducts and alveoli. |
| Define pleural pressure | Pleural pressure is the pressure of fluid within the space between the lungs and chest wall. Normally negative, therefore creating a suction effect. |
| Define alveolar pressure | Alveolar pressure is the pressure of air inside the alveoli. It is negative during inspiration and positive during expiration. |
| Describe mechanics of inspiration | In inspiration alveolar pressure is negative, resulting in a pressure gradient that results in airflow into the lungs. |
| Describe mechanics of expiration | In expiration alveolar pressure rises above atmospheric pressure, becoming positive, resulting in a pressure gradient that results in airflow out of the lungs |
| What are the mechanics of 'normal' breathing? | Normal breathing at rest uses the lung movement methods where the diaphragm contracts to initiate inspiration and then relaxes for expiration, with assistance from elastic recoil of lungs and chest wall. |
| Define lung compliance | Lungs are elastic structures with a tendency to collapse in the absence of any force(s) to keep them inflated, which has advantages during passive expiration. |
| What is the formula for lung compliance? | Formula - Compliance = volume/pressure |
| What are the determinants of lung compliance? | Elastic forces of lung tissue – determined by the ratio of elastin and collagen fibres. Surface tension of fluid lining the alveoli |
| Define the key measures of lung volume | Tidal volume (VT or TV): the volume inhaled and exhaled during normal breathing Inspiratory reserve volume (IRV): the maximum volume above the tidal volume that we can inhale into our lungs. Expiratory reserve volume (ERV): the maximum volume that we can exhale from our lungs at the end of a normal breath. Residual volume (RV): the volume of air remaining in the lungs after a full expiration. We can never empty them completely. |
| Define the key measures of lung capacity | Expiratory capacity (EC): all the air breathed out in a maximal exhalation after a normal breath (VT + ERV) Functional residual capacity (FRC): the volume of air remaining in the lungs at the end of a normal expiration (ERV + RV). Total lung capacity (TLC): all the air that it is possible for the lungs to contain (RV + ERV + VT + IRV). Vital capacity (VC): all the air that can be expired from a maximal inhalation (ERV + VT + IRV). Inspiratory capacity (IC): all the air breathed in during a maximal inhalation at the end of a normal exhalation (VT + IRV). |
