Phases of the Cardiac Cycle
Lung Volumes and Capacities
The amount of air in the lungs can be subdivided into four (4) volumes and four (4) capacities.
Respiratory (lung) volumes:
- Tidal volume (TV) is the amount of air that can be inhaled and exhaled during one normal (quiet) breathing cycle (about 500 ml for men & women).
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- Inspiratory reserve volume (IRV) is the amount of air that can be forcibly inhaled beyond a tidal inhalation (about 3,000 ml for men & 2,000 ml for women).
- Expiratory reserve volume (ERV) is the amount of air that can be forcibly exhaled beyond a tidal exhalation (about 1200 ml for men & 700 ml for women).
- Residual Volume (RV) (see image below)– the amount of air remaining in the lungs after an ERV (= about 1,200 ml in men & women).
- Respiratory (lung) capacities (= two or more respiratory volumes added together):1. Inspiratory capacity = TV + IRV.2. Functional reserve capacity = ERV + RV.
3. Vital capacity (see image below) = TV + IRV + ERV.
4. Total lung capacity = RV + VC.