lab 51: Breathing and Respiratory Volumes

thoracic cavity increases during inspiration by contraction of inspiration muscles or diaphragm. External intercostals help widen the thoracic cavity. Sternum and rib cage elevate because of contractions of sternocleidomastoid, scalenes, pectoralis minor, and intercartilaginous part of internal intercostals.

Mechanism for inspiration

cannot be calculated with a spirometer

calculate functional residual capacity using data obtained from respiratory volumes

IC = TV + IRV

calculate inspiratory capacity using data obtained from respiratory volumes

VC-(TV+ERV) = IRV

calculate inspiratory reserve volume using data obtained from respiratory volumes

Volume of air in addition to tidal volume that leaves the lungs during forced expiration

expiratory reserve volume

volume of air that remains in the lungs following the exhalation of tidal volume

functional residual capacity

maximum volume of air a person can inhale following exhalation of tidal volume

inspiratory capacity

Volume of air in addition to tidal volume that enters lungs during forced inspiration

inspiratory reserve volume

1. breathe normally for a few minutes and set the needle to 0 2. at the end of ordinary expiration, place mouthpiece between lips and exhale as much as possible. pinch nose to prevent air from escaping 3. record

measure expiratory reserve volume using a spirometer

1. sit quietly 2. position spirometer dial to 0 3. exhale 3 expirations after inhaling each time 4. divide the total value on the needle by 3 and record as resting tidal volume

measure tidal volume using a spirometer

1. breath normally for a few moments and set the needle to 0 2. breathe in and out deeply a couple times, then take the deepest breath possible 3.place mouthpiece between lips and exhale all air out of lungs slowly and forcefully 4. record

measure vital capacity using a spirometer

interosseous part of internal intercostals depress the ribcage which narrows the thoracic cavity. rectus abdominis and external oblique compresses abdominal viscera forcing diaphragm to ascend and reduce the size of thoracic cavity

mechanism for expiration

volume of air that always remains in the lungs after the most forceful expiration

residual volume

Volume of air that enters or leaves the lungs during one respiratory cycle (one inspiration and expiration)

tidal volume

maximum volume of air that can be exhaled after taking the deepest breath possible

vital capacity