Biology · Breathing and Exchange of Gases · NEET
IRV (Inspiratory Reserve Volume) is the EXTRA air you can breathe IN after a normal breath, by forcing a deep breath - about 2500 to 3000 mL. ERV (Expiratory Reserve Volume) is the EXTRA air you can breathe OUT after a normal breath, by forcing a hard breath - about 1000 to 1100 mL. Simple rule: I in IRV = In (breathe in extra), E in ERV = Expire/Exit (breathe out extra). IRV is much bigger than ERV.
No, this is the most common mix-up. RESERVE volumes (IRV and ERV) are EXTRA air you can still move with force. RESIDUAL Volume (RV) is air that STAYS in the lungs even after the hardest possible expiration and can never leave. So reserve = movable extra air; residual = trapped leftover air. RV keeps the alveoli from collapsing.
Even after the most forceful expiration, the airways and alveoli still hold some air because the lungs never fully squeeze flat. This trapped air is the Residual Volume (1100-1200 mL). It stays behind so the alveoli remain slightly inflated and do not collapse, and it also lets gas exchange continue between breaths. Because it cannot be pushed out, RV is never part of Vital Capacity.
IRV is the LARGEST volume at 2500-3000 mL, because your lungs have a lot of room to take in extra air. TV is the SMALLEST at only about 500 mL, since quiet breathing moves very little air. ERV (1000-1100 mL) and RV (1100-1200 mL) are close in size and sit in the middle. Order from small to large: TV < ERV < RV < IRV.
TV = approx 500 mL; IRV = 2500 to 3000 mL; ERV = 1000 to 1100 mL; RV = 1100 to 1200 mL. NEET repeatedly asks match-the-column questions using these exact ranges, so learn the numbers, not just the definitions. Notice ERV and RV overlap around 1100 mL - examiners use this closeness to trap you.
Match List-I with List-II. List-I (Respiratory Volume): A. ERV B. RV C. IRV D. TV List-II (Capacity in mL): I. 2500-3000 mL II. 500 mL III. 1000-1100 mL IV. 1100-1200 mL Choose the correct answer:
Lungs are made up of air-filled sacs, the alveoli. They do not collapse even after forceful expiration, because of:
Match Column I with Column II: Column I: a. Tidal volume b. Inspiratory Reserve Volume c. Expiratory Reserve Volume d. Residual volume Column II: i. 2500-3000 mL ii. 1100-1200 mL iii. 500-550 mL iv. 1000-1100 mL
Try the real previous-year questions from this chapter — each with the answer and a full solution.
Tidal Volume (TV), Inspiratory Reserve Volume (IRV), Expiratory Reserve Volume (ERV) and Residual Volume (RV). Together they describe how much air the lungs move and hold. When two or more are added together, they form respiratory capacities.
About 500 mL. This is the air moved in or out during one normal quiet breath. A healthy person moves roughly 6000 to 8000 mL of air per minute at rest.
No. Vital Capacity = IRV + TV + ERV only. Residual Volume can never be exhaled, so it is left out of Vital Capacity. RV is included only in Total Lung Capacity.
A volume is a single quantity of air (like TV or RV). A capacity is the SUM of two or more volumes (like Vital Capacity or Total Lung Capacity). Learn the four volumes first, then build the capacities from them.
Tidal Volume, about 500 mL. IRV and ERV only come into play during deep forced breaths, and RV never leaves the lungs at all.
