Breathing and Exchange of Gases
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During forceful expiration, abdominal muscles and internal inter-costal
muscles contract..
- Respiratory cycle= an inspiration + an expiration
- Normal respiratory (breathing) rate: 12-16 times/min
- Spirometer (respirometer): To measure respiratory rate.
RËSPÏRÅTØRÝ VØLÜMËS ÅÑD ÇÅPÅÇÏTÏËS
Tidal volume (TV) : Volume of air inspired or expired during a normal
respiration. It is about 500 ml, i.e., 6000-8000 ml per minute.
Inspiratory reserve volume (IRV) or complemental air : Additional
volume of air that a person can inspire by forceful inspiration. It is 2500-
3000 ml.
Expiratory reserve volume (ERV) or supplemental air : Additional volume
of air that a person can expire by a forceful expiration. It is 1000-1100 ml.
Residual volume (RV): Volume of air remaining in lungs after a forcible
expiration. It is 1100-1200 ml. [NEET 2017]
Inspiratory capacity (IC) : Total volume of air inspired after a normal
expiration (TV + IRV). It is 3000-3500 ml.
Expiratory capacity (EC) : Total volume of air expired after a normal
inspiration (TV + ERV). It is 1500-1600 ml. [NEET 2019]
Functional residual capacity (FRC) : Volume of air remaining in the
lungs after a normal expiration (ERV + RV). It is 2100-2300 ml.
Vital capacity (VC) : Maximum volume of air that a person can breathe
in after a forced expiration or maximum volume of air that a person can
breathe out after a forced inspiration (ERV + TV + IRV). It is 4000-4600 ml.
[AIPMT 2009]
Total lung capacity (TLC) : Total volume of air in the lungs after the end
of a forced inspiration. (RV + ERV + TV + IRV or VC + RV). It is 5000-6000 ml.
Part of respiratory tract (from nostrils to terminal bronchi) not involved
in gaseous exchange is called dead space. Dead air volume is about
150 ml.
GÅS ËXÇHÅÑGË
Gas exchange occurs between:
Alveoli and blood
Blood and tissues
Alveoli are the primary sites of gas exchange. O2 & CO2 are exchanged by
simple diffusion. It depends upon the following factors: