Question

Vital capacity decreases with age (say after age 20), but TLC does not decrease. What changes in the lung volumes (TV/ERV/IRV/RV) contribute to VC are most likely to change with age to make the preceding statement true?

Answer 1

Answer:- with aging , total lung capacity remains same but vital capacity decreases. Lung maturation occurs by the time about 20-25 years old . After about the age of 35, lung function starts decreasing. There are several body changes occurring in the body with age that decreases the lung capacity:-

1. The diaphragm that moves air in and out of the lungs , gets weaker, decreasing the ability to inhale and exhale.

2. Ribcage bone becomes thinner and changes its shape with aging, so that it is less able to contract and expand with breathing.

3. Muscles and tissues that usually keep the airway open lose elasticity, causing the airways to close.

4. Alveoli where exchange of gases take place loose their shape and becomes baggy.

5. The part of the brain that controls breathing may no longer send as strong or clear signals to the lungs.

Due to the above changes, the efficiency of inhalation and exhalation decreases, thus vital capacity also decreases.

* Total Lung capacity is the total amount of air that the lung can hold.

( Total Lung capacity= vital capacity+reserve volume)

All the changes described above decreases the vital capacity but they also cause air to get trapped, decreasing the amount of oxygen moving in and carbon dioxide moving out of blood stream. This trapping causes residual volume to get increased. Thus total Lung capacity doesn't change with age and the TLC value remains unchanged.

TLC=VC+RV

VC =TV+IRV+ERV

Since vital capacity decreases, tidal Volume, inspiratory reserve volume and expiratory reserve volume also decreases.

Thus, VC decreases because-

1. TV decreases

2. ERV decreases

3. IRV decreases

4. RV increases