Important Questions Class 11 Biology Chapter 14 Breathing and Exchange of Gases With Answers

Breathing is the exchange of oxygen from the atmosphere with carbon dioxide produced by body cells. Lungs, alveoli, haemoglobin, pressure gradients, and respiratory centres support gas exchange in humans.

Every breath depends on pressure change, diffusion, haemoglobin, and brain regulation. Important Questions Class 11 Biology Chapter 14 help students prepare Breathing and Exchange of Gases for CBSE 2026-27 school exams, NEET foundation practice, and NCERT-based state board tests. The chapter carries diagram-based, formula-based, definition-based, and reasoning questions from respiratory organs, pulmonary ventilation, respiratory volumes, alveolar diffusion, oxygen transport, carbon dioxide transport, respiratory rhythm, asthma, emphysema, and occupational lung disorders.

Key Takeaways

• Breathing Rate: A healthy human breathes about 12-16 times per minute.
• Tidal Volume: A normal breath moves about 500 mL of air.
• Oxygen Transport: About 97 percent of oxygen travels through RBCs.
• Carbon Dioxide Transport: About 70 percent of carbon dioxide travels as bicarbonate.

Important Questions Class 11 Biology Chapter 14 Structure 2026

Important Questions Class 11 Biology Chapter 14 for CBSE 2026-27

The chapter becomes simple when students separate breathing from cellular respiration. Breathing moves gases between lungs and atmosphere, while cellular respiration uses O₂ inside cells.

1. What is breathing in Class 11 Biology?

Breathing is the exchange of atmospheric O₂ with CO₂ produced by body cells. It is commonly called respiration in daily language.

1. O₂ enters the body during inspiration.
2. CO₂ leaves the body during expiration.
3. Breathing supports cellular respiration.
4. Cellular respiration releases energy from food molecules.

Final answer: Breathing exchanges O₂ and CO₂ between the body and atmosphere.

2. Why do cells need continuous oxygen supply?

Cells need O₂ to break down molecules like glucose, amino acids, and fatty acids for energy. CO₂ forms during these catabolic reactions.

1. O₂ supports oxidation of food molecules.
2. Cells release energy through cellular respiration.
3. CO₂ forms as a harmful waste.
4. The respiratory system removes CO₂.

Final fact: O₂ supply and CO₂ removal must continue throughout life.

3. What are the five steps of respiration in humans?

Human respiration includes breathing, gas diffusion, blood transport, tissue diffusion, and cellular oxygen use.

1. Pulmonary ventilation draws air in and releases alveolar air.
2. O₂ and CO₂ diffuse across alveolar membranes.
3. Blood transports O₂ and CO₂.
4. Gases diffuse between blood and tissues.
5. Cells use O₂ and release CO₂.

Final answer: Respiration has five linked steps from breathing to cellular respiration.

Respiratory Organs Class 11 Biology Questions

Different animals use different respiratory surfaces based on habitat and body organisation. NCERT 2026 expects students to match organisms with their respiratory structures.

4. How do lower invertebrates exchange gases?

Lower invertebrates exchange gases by simple diffusion across the body surface.

1. Sponges use body surface diffusion.
2. Coelenterates use body surface diffusion.
3. Flatworms use body surface diffusion.
4. Their body organisation supports direct diffusion.

Final fact: Simple diffusion works in animals with simpler body organisation.

5. What are the respiratory organs in earthworms, insects, fishes, and frogs?

Earthworms use moist cuticle, insects use tracheal tubes, fishes use gills, and frogs use lungs and moist skin.

1. Earthworm: moist cuticle.
2. Insects: tracheal tubes.
3. Aquatic arthropods and molluscs: gills.
4. Terrestrial vertebrates: lungs.
5. Frogs: lungs and cutaneous respiration.

Final answer: Respiratory organs vary with habitat and organisation.

6. What is branchial respiration?

Branchial respiration is gaseous exchange through gills.

1. Gills are vascularised structures.
2. Most aquatic arthropods use gills.
3. Most molluscs use gills.
4. Fishes also use gills.

Final fact: Gills support gas exchange in many aquatic animals.

7. What is pulmonary respiration?

Pulmonary respiration is gaseous exchange through lungs.

1. Lungs are vascularised bags.
2. Terrestrial forms commonly use lungs.
3. Amphibians, reptiles, birds, and mammals use lungs.
4. Human respiration occurs through lungs.

Final fact: Pulmonary respiration occurs through lungs.

Human Respiratory System Class 11 Biology Questions

The human respiratory system has a conducting part and an exchange part. The conducting part prepares air, while alveoli perform actual gas exchange.

8. Write the pathway of air in the human respiratory system.

Air passes through nostrils, nasal chamber, pharynx, larynx, trachea, bronchi, bronchioles, and alveoli.

1. External nostrils receive atmospheric air.
2. Nasal passage leads to nasal chamber.
3. Nasal chamber opens into pharynx.
4. Pharynx opens into larynx.
5. Larynx connects to trachea.
6. Trachea divides into right and left bronchi.
7. Bronchi branch into bronchioles.
8. Terminal bronchioles lead to alveoli.

Final answer: Alveoli are the final air-exchange structures.

9. What is the larynx?

Larynx is a cartilaginous box that helps in sound production. It is also called the sound box.

1. It lies between pharynx and trachea.
2. Air passes through the larynx region.
3. It supports voice production.
4. It has a glottis opening.

Final fact: Larynx produces sound in humans.

10. What is the function of epiglottis?

Epiglottis prevents food from entering the larynx during swallowing.

1. It is a thin elastic cartilaginous flap.
2. It covers the glottis during swallowing.
3. It directs food away from the respiratory passage.
4. It protects the airway.

Final answer: Epiglottis prevents food entry into the larynx.

11. What are alveoli?

Alveoli are thin, irregular-walled, vascularised bag-like structures where gas exchange occurs.

1. Terminal bronchioles give rise to alveoli.
2. Alveoli form the exchange part of the respiratory system.
3. They allow diffusion of O₂ and CO₂.
4. They connect air with blood capillaries.

Final fact: Alveoli are the primary sites of gaseous exchange.

12. What is pleura?

Pleura is a double-layered membrane that covers the lungs. Pleural fluid lies between its two layers.

1. Outer pleural membrane touches the thoracic lining.
2. Inner pleural membrane touches the lung surface.
3. Pleural fluid reduces friction.
4. It supports smooth lung movement.

Final answer: Pleura reduces friction on the lung surface.

13. What is the conducting part of the respiratory system?

The conducting part extends from external nostrils to terminal bronchioles.

1. It transports atmospheric air to alveoli.
2. It clears air of foreign particles.
3. It humidifies air.
4. It brings air to body temperature.

Final fact: The conducting part prepares air before gas exchange.

14. What is the exchange part of the respiratory system?

The exchange part includes alveoli and their ducts. It performs actual diffusion of gases.

1. O₂ diffuses from alveoli to blood.
2. CO₂ diffuses from blood to alveoli.
3. Thin alveolar walls support diffusion.
4. Blood capillaries surround alveoli.

Final answer: The exchange part performs actual O₂ and CO₂ diffusion.

Mechanism of Breathing Class 11 Biology Questions

Breathing depends on pressure gradients between lungs and atmosphere. Inspiration occurs when lung pressure falls, while expiration occurs when lung pressure rises.

15. What is inspiration?

Inspiration is the process in which atmospheric air enters the lungs.

1. Diaphragm contracts.
2. External intercostal muscles contract.
3. Thoracic volume increases.
4. Pulmonary volume increases.
5. Intra-pulmonary pressure falls below atmospheric pressure.
6. Air moves into the lungs.

Final fact: Inspiration occurs due to negative pressure inside lungs.

16. What is expiration?

Expiration is the process in which alveolar air moves out of the lungs.

1. Diaphragm relaxes.
2. Intercostal muscles relax.
3. Thoracic volume decreases.
4. Pulmonary volume decreases.
5. Intra-pulmonary pressure rises above atmospheric pressure.
6. Air moves out of the lungs.

Final fact: Expiration occurs when intra-pulmonary pressure exceeds atmospheric pressure.

17. Explain the process of inspiration under normal conditions.

Inspiration starts when diaphragm and external intercostal muscles contract. This increases thoracic and pulmonary volume.

1. Diaphragm contraction increases antero-posterior thoracic volume.
2. External intercostal muscles lift ribs and sternum.
3. Dorso-ventral thoracic volume increases.
4. Pulmonary volume increases with thoracic volume.
5. Intra-pulmonary pressure becomes lower than atmospheric pressure.
6. Air enters the lungs.

Final answer: Normal inspiration occurs through pressure reduction inside the lungs.

18. Explain expiration under normal conditions.

Expiration starts when diaphragm and intercostal muscles relax. This reduces thoracic and pulmonary volume.

1. Diaphragm returns to normal position.
2. Sternum and ribs return to normal position.
3. Thoracic volume decreases.
4. Pulmonary volume decreases.
5. Intra-pulmonary pressure rises slightly above atmospheric pressure.
6. Air leaves the lungs.

Final answer: Normal expiration occurs through pressure increase inside the lungs.

19. What muscles help in breathing?

Diaphragm and intercostal muscles help generate breathing pressure gradients.

1. Diaphragm changes antero-posterior thoracic volume.
2. External intercostal muscles lift ribs and sternum.
3. Internal intercostal muscles support expiration.
4. Abdominal muscles help forceful breathing.

Final fact: Breathing muscles alter thoracic volume.

20. What is the normal breathing rate in healthy humans?

A healthy human breathes about 12-16 times per minute.

1. Breathing rate changes with activity.
2. Exercise increases tissue oxygen demand.
3. Neural centres regulate rhythm.
4. Clinical assessment may use spirometry.

Final answer: Normal breathing rate is 12-16 breaths per minute.

Respiratory Volumes and Capacities Class 11 Biology Questions

Respiratory values often appear as direct numerical questions. Learn every term with its formula and approximate NCERT value.

21. What is tidal volume Class 11 Biology?

Tidal volume is the volume of air inspired or expired during normal breathing. Its approximate value is 500 mL.

1. It applies to quiet breathing.
2. A healthy person breathes 12-16 times per minute.
3. Minute ventilation uses tidal volume and breathing rate.

Formula:
Tidal air per minute = TV × Breathing rate

Calculation:
500 mL × 12 to 16 = 6000 to 8000 mL per minute

Final result: Tidal volume is about 500 mL.

22. Find the tidal volume of a healthy human in one hour.

A healthy human moves about 360-480 litres of air in one hour through normal breathing.

Given Data:

1. Tidal volume = 500 mL.
2. Breathing rate = 12-16 breaths per minute.
3. Time = 60 minutes.

Formula Used:
Tidal air per hour = TV × Breathing rate × 60

Calculation:
500 × 12 × 60 = 360000 mL = 360 L
500 × 16 × 60 = 480000 mL = 480 L

Final Result: Tidal volume per hour = 360-480 L.

23. What is inspiratory reserve volume?

Inspiratory reserve volume is the extra air a person can inspire by forceful inspiration.

1. It is measured after normal inspiration.
2. Its average value is 2500-3000 mL.
3. It increases air intake during deep breathing.

Final answer: IRV is about 2500-3000 mL.

24. What is expiratory reserve volume?

Expiratory reserve volume is the extra air a person can expire by forceful expiration.

1. It is measured after normal expiration.
2. Its average value is 1000-1100 mL.
3. It supports forceful breathing assessment.

Final answer: ERV is about 1000-1100 mL.

25. What is residual volume?

Residual volume is the air remaining in the lungs after forceful expiration.

1. It prevents complete lung collapse.
2. Its average value is 1100-1200 mL.
3. It remains after maximum expiration.

Final answer: RV is about 1100-1200 mL.

26. What is the volume of air remaining after normal breathing?

Functional residual capacity remains in the lungs after normal expiration. It includes ERV and RV.

Formula:
FRC = ERV + RV

Using NCERT values:
ERV = 1000-1100 mL
RV = 1100-1200 mL

Final result: FRC is about 2100-2300 mL.

27. What is inspiratory capacity?

Inspiratory capacity is the total air a person can inspire after normal expiration.

Formula:
IC = TV + IRV

Components:

1. TV = tidal volume.
2. IRV = inspiratory reserve volume.

Final answer: Inspiratory capacity equals TV + IRV.

28. What is expiratory capacity?

Expiratory capacity is the total air a person can expire after normal inspiration.

Formula:
EC = TV + ERV

Components:

1. TV = tidal volume.
2. ERV = expiratory reserve volume.

Final answer: Expiratory capacity equals TV + ERV.

29. What is vital capacity Class 11 Biology?

Vital capacity is the maximum air a person can breathe out after forced inspiration or breathe in after forced expiration.

Formula:
VC = ERV + TV + IRV

Components:

1. ERV = expiratory reserve volume.
2. TV = tidal volume.
3. IRV = inspiratory reserve volume.

Final answer: Vital capacity equals ERV + TV + IRV.

30. What is total lung capacity?

Total lung capacity is the total air accommodated in lungs after forced inspiration.

Formula:
TLC = RV + ERV + TV + IRV

Alternative formula:
TLC = VC + RV

Final answer: Total lung capacity equals vital capacity plus residual volume.

Exchange of Gases Class 11 Biology Questions

Gas exchange works through diffusion across thin membranes. NCERT values for partial pressure help explain why O₂ enters blood and CO₂ leaves blood.

31. Why does diffusion of gases occur only in alveolar region?

Alveoli provide the thin, vascularised, and pressure-gradient-rich surface needed for gas diffusion.

1. Alveoli have thin squamous epithelium.
2. Alveoli have rich capillary supply.
3. Their membrane is less than a millimetre thick.
4. Partial pressure gradients exist across alveoli.
5. Conducting parts do not perform actual exchange.

Final answer: Alveoli are the primary sites of gas exchange.

32. What factors affect diffusion of gases?

Gas diffusion depends on partial pressure gradient, gas solubility, and membrane thickness.

1. Higher pressure gradient increases diffusion.
2. Higher solubility increases diffusion.
3. Thinner membrane increases diffusion.
4. Alveolar membrane supports rapid diffusion.

Final fact: CO₂ diffuses faster because it is more soluble than O₂.

33. What is partial pressure?

Partial pressure is the pressure contributed by one gas in a mixture of gases.

1. Oxygen partial pressure is written as pO₂.
2. Carbon dioxide partial pressure is written as pCO₂.
3. Partial pressure decides gas diffusion direction.
4. Gases move from higher partial pressure to lower partial pressure.

Final fact: Partial pressure gradients drive respiratory gas exchange.

34. Compare pO₂ and pCO₂ in atmospheric and alveolar air.

Atmospheric air has higher pO₂ and lower pCO₂ than alveolar air.

Values:

1. Atmospheric pO₂ = 159 mm Hg.
2. Alveolar pO₂ = 104 mm Hg.
3. Atmospheric pCO₂ = 0.3 mm Hg.
4. Alveolar pCO₂ = 40 mm Hg.

Final answer: Atmospheric pO₂ is higher, and atmospheric pCO₂ is lower.

35. Why does oxygen diffuse from alveoli to blood?

O₂ diffuses from alveoli to blood because alveolar pO₂ is higher than deoxygenated blood pO₂.

Values:

1. Alveolar pO₂ = 104 mm Hg.
2. Deoxygenated blood pO₂ = 40 mm Hg.
3. O₂ moves down the pressure gradient.

Final answer: O₂ moves from alveoli to blood due to higher alveolar pO₂.

36. Why does carbon dioxide diffuse from blood to alveoli?

CO₂ diffuses from blood to alveoli because deoxygenated blood pCO₂ is higher than alveolar pCO₂.

Values:

1. Deoxygenated blood pCO₂ = 45 mm Hg.
2. Alveolar pCO₂ = 40 mm Hg.
3. CO₂ moves down its pressure gradient.

Final answer: CO₂ moves from blood to alveoli due to higher blood pCO₂.

Transport of Oxygen Class 11 Biology Questions

O₂ mainly travels through haemoglobin inside RBCs. Its loading and unloading depend on pO₂, pCO₂, H⁺ concentration, and temperature.

37. How is oxygen transported in blood?

About 97 percent of O₂ is transported by RBCs, and 3 percent dissolves in plasma.

1. Haemoglobin binds O₂ reversibly.
2. Oxyhaemoglobin forms in lungs.
3. O₂ dissociates in tissues.
4. Plasma carries a small dissolved fraction.

Final answer: Most O₂ travels as oxyhaemoglobin in RBCs.

38. What is oxyhaemoglobin?

Oxyhaemoglobin is the reversible compound formed when O₂ binds with haemoglobin.

1. Haemoglobin contains iron.
2. Each haemoglobin molecule carries up to four O₂ molecules.
3. Binding occurs strongly at high pO₂.
4. Dissociation occurs at low pO₂.

Final fact: Oxyhaemoglobin forms at the lung surface.

39. What is oxygen dissociation curve Class 11 Biology?

Oxygen dissociation curve shows percentage saturation of haemoglobin with O₂ at different pO₂ values.

1. It has a sigmoid shape.
2. It shows haemoglobin oxygen binding.
3. It shows O₂ release in tissues.
4. It helps study effects of pCO₂, H⁺ and temperature.

Final answer: The oxygen dissociation curve is sigmoid.

40. Why is oxygen dissociation curve sigmoid?

The oxygen dissociation curve is sigmoid because haemoglobin shows cooperative oxygen binding.

1. First O₂ binding increases affinity for later O₂ molecules.
2. High pO₂ favours oxyhaemoglobin formation.
3. Low pO₂ favours O₂ release.
4. Tissue conditions shift O₂ unloading.

Final fact: Sigmoid shape reflects cooperative binding by haemoglobin.

41. What conditions favour oxyhaemoglobin formation?

High pO₂, low pCO₂, low H⁺ concentration, and lower temperature favour oxyhaemoglobin formation.

Location:

1. Alveoli have high pO₂.
2. Alveoli have low pCO₂.
3. Alveoli have lower H⁺ concentration.
4. Alveolar conditions support O₂ loading.

Final answer: Oxyhaemoglobin forms mainly in alveoli.

42. What conditions favour oxygen dissociation in tissues?

Low pO₂, high pCO₂, high H⁺ concentration, and higher temperature favour O₂ release.

Location:

1. Tissues have lower pO₂.
2. Tissues have higher pCO₂.
3. Tissues have higher H⁺ concentration.
4. Tissue metabolism raises temperature.

Final fact: O₂ dissociates from oxyhaemoglobin in tissues.

43. How much oxygen does 100 mL oxygenated blood deliver to tissues?

Every 100 mL of oxygenated blood delivers about 5 mL of O₂ to tissues.

1. Haemoglobin carries O₂ from lungs.
2. Tissue conditions favour O₂ unloading.
3. O₂ diffuses into tissue cells.

Final answer: 100 mL oxygenated blood delivers around 5 mL O₂.

Transport of Carbon Dioxide Class 11 Biology Questions

CO₂ travels mainly as bicarbonate, with smaller amounts through haemoglobin and plasma. Carbonic anhydrase makes bicarbonate transport fast.

44. What are the major transport mechanisms for CO₂?

CO₂ travels as bicarbonate, carbamino-haemoglobin, and dissolved CO₂ in plasma.

1. About 70 percent travels as bicarbonate.
2. About 20-25 percent binds haemoglobin.
3. About 7 percent dissolves in plasma.
4. RBCs contain carbonic anhydrase.

Final answer: Bicarbonate is the main form of CO₂ transport.

45. How is carbon dioxide transported as bicarbonate?

CO₂ forms bicarbonate inside RBCs with the help of carbonic anhydrase.

Reaction:
CO₂ + H₂O ⇌ H₂CO₃ ⇌ HCO₃⁻ + H⁺

1. CO₂ diffuses into blood at tissues.
2. Carbonic anhydrase speeds carbonic acid formation.
3. Carbonic acid dissociates into bicarbonate and H⁺.
4. At alveoli, the reaction reverses.
5. CO₂ releases into alveolar air.

Final answer: Carbonic anhydrase supports bicarbonate transport of CO₂.

46. What is carbamino-haemoglobin?

Carbamino-haemoglobin forms when CO₂ binds with haemoglobin.

1. About 20-25 percent CO₂ travels this way.
2. Binding increases when pCO₂ is high.
3. Binding increases when pO₂ is low.
4. Tissue conditions favour its formation.
5. Alveolar conditions favour CO₂ release.

Final fact: Carbamino-haemoglobin carries part of CO₂ in blood.

47. How much CO₂ does 100 mL deoxygenated blood deliver to alveoli?

Every 100 mL of deoxygenated blood delivers about 4 mL of CO₂ to alveoli.

1. CO₂ reaches lungs through blood.
2. Alveolar pCO₂ is lower.
3. CO₂ diffuses from blood to alveoli.
4. Expiration removes it.

Final answer: 100 mL deoxygenated blood delivers about 4 mL CO₂.

48. What is the effect of pCO₂ on oxygen transport?

High pCO₂ reduces haemoglobin affinity for O₂ and promotes O₂ release in tissues.

1. Tissues have high pCO₂.
2. H⁺ concentration also rises.
3. These conditions favour oxyhaemoglobin dissociation.
4. O₂ reaches active tissues.

Final fact: High pCO₂ supports O₂ unloading.

Regulation of Respiration Class 11 Biology Questions

Respiratory rhythm changes with tissue demand. Brain centres and chemosensitive regions adjust breathing mainly through CO₂ and H⁺ levels.

49. How is respiration regulated?

Respiration is regulated by neural centres in the medulla and pons.

1. Respiratory rhythm centre lies in medulla.
2. It controls basic breathing rhythm.
3. Pneumotaxic centre lies in pons.
4. It moderates rhythm centre function.
5. Chemosensitive area detects CO₂ and H⁺ changes.

Final answer: Medulla and pons regulate respiratory rhythm.

50. What is the respiratory rhythm centre?

Respiratory rhythm centre is a specialised centre in the medulla that controls breathing rhythm.

1. It maintains basic rhythm.
2. It responds to body demands.
3. It receives signals from chemosensitive regions.
4. It adjusts respiratory process.

Final fact: The medulla contains the main rhythm centre.

51. What is pneumotaxic centre?

Pneumotaxic centre is a pons region centre that moderates respiratory rhythm.

1. It sends neural signals to the rhythm centre.
2. It can reduce inspiration duration.
3. It can alter respiratory rate.
4. It fine-tunes breathing.

Final fact: Pneumotaxic centre lies in the pons.

52. Why is oxygen less important in regulating breathing rhythm?

O₂ has an insignificant role in normal respiratory rhythm regulation. CO₂ and H⁺ changes act more strongly.

1. Chemosensitive area responds to CO₂.
2. It also responds to H⁺ concentration.
3. Aortic and carotid receptors detect these changes.
4. Rhythm centre makes necessary adjustments.

Final answer: CO₂ and H⁺ mainly regulate breathing rhythm.

Respiratory Disorders Class 11 Biology Questions

Respiratory disorders often connect symptoms with affected structures. CBSE 2026 questions may ask asthma, emphysema, and occupational lung damage.

53. What is asthma?

Asthma is difficulty in breathing with wheezing due to inflammation of bronchi and bronchioles.

1. Airways become inflamed.
2. Air movement becomes difficult.
3. Wheezing occurs during breathing.
4. Bronchi and bronchioles are affected.

Final answer: Asthma affects bronchi and bronchioles.

54. What is emphysema?

Emphysema is a chronic disorder where alveolar walls get damaged.

1. Respiratory surface decreases.
2. Gas exchange becomes less efficient.
3. Cigarette smoking is a major cause.
4. Alveoli lose functional surface area.

Final fact: Emphysema reduces respiratory surface.

55. What are occupational respiratory disorders?

Occupational respiratory disorders occur due to long exposure to industrial dust.

1. Grinding industries can produce heavy dust.
2. Stone-breaking industries can produce heavy dust.
3. Dust overloads body defence mechanisms.
4. Inflammation can lead to fibrosis.
5. Fibrosis causes serious lung damage.

Final fact: Workers in dusty industries should wear protective masks.

56. What happens to respiratory process when a person goes up a hill?

Breathing rate increases when a person goes up a hill because oxygen availability decreases.

1. Higher altitude has lower oxygen partial pressure.
2. Less O₂ enters blood.
3. Body tissues need O₂ supply.
4. Respiratory rate increases to compensate.

Final answer: Hill climbing increases breathing rate due to lower oxygen availability.

Class 11 Biology Breathing and Exchange of Gases Questions With Answers for Board Practice

NCERT exercise questions from this chapter often test formulas and exact values. Keep units clear because respiratory volumes and partial pressures depend on them.

57. Distinguish between IRV and ERV.

IRV is extra inspired air, while ERV is extra expired air.

Final fact: IRV is larger than ERV in NCERT values.

58. Distinguish between inspiratory capacity and expiratory capacity.

Inspiratory capacity measures maximum air inspired after normal expiration, while expiratory capacity measures maximum air expired after normal inspiration.

Final fact: IC and EC use tidal volume in their formulas.

59. Distinguish between vital capacity and total lung capacity.

Vital capacity excludes residual volume, while total lung capacity includes residual volume.

Final fact: TLC equals VC + RV.

60. Why is a spirometer used?

A spirometer measures respiratory volumes and supports clinical assessment of pulmonary functions.

1. It estimates air involved in breathing movements.
2. It helps assess lung performance.
3. It supports diagnosis of respiratory problems.
4. It measures values like TV, IRV, and ERV.

Final answer: Spirometer assesses pulmonary function.

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