What is the primary organ of the respiratory system?
A) Heart
B) Lung ✅
C) Kidney
D) Liver Explanation: Lungs are the primary organs responsible for gas exchange.
What gas do we inhale to survive?
A) Carbon dioxide
B) Oxygen ✅
C) Nitrogen
D) Hydrogen Explanation: Oxygen is essential for cellular respiration and energy production.
Which structure connects the throat to the lungs?
A) Esophagus
B) Bronchi
C) Trachea ✅
D) Larynx Explanation: The trachea (windpipe) conducts air to the bronchi.
Where does gas exchange occur in the lungs?
A) Trachea
B) Bronchioles
C) Alveoli ✅
D) Pleura Explanation: Alveoli are tiny sacs where oxygen and carbon dioxide exchange.
Which muscle helps in breathing?
A) Biceps
B) Diaphragm ✅
C) Hamstring
D) Deltoid Explanation: The diaphragm contracts and relaxes to allow inhalation and exhalation.
What is the process of taking air into the lungs called?
A) Exhalation
B) Respiration
C) Inhalation ✅
D) Circulation Explanation: Inhalation is the act of breathing in air.
How many lungs does a human have?
A) 1
B) 2 ✅
C) 3
D) 4 Explanation: Humans have two lungs – one on each side of the chest.
What protects the lungs inside the chest cavity?
A) Skull
B) Vertebral column
C) Rib cage ✅
D) Pelvic girdle Explanation: The rib cage encloses and protects the lungs and heart.
Which part of the respiratory system filters dust and microbes?
A) Alveoli
B) Trachea
C) Nasal cavity ✅
D) Lungs Explanation: The nasal cavity has mucus and cilia to trap particles.
What gas is expelled from the body during exhalation?
A) Oxygen
B) Hydrogen
C) Carbon dioxide ✅
D) Nitrogen Explanation: Carbon dioxide is a waste product of respiration.
What is the tube that carries air from the trachea into the lungs?
A) Bronchi ✅
B) Esophagus
C) Diaphragm
D) Larynx Explanation: The bronchi branch off the trachea and enter the lungs.
Which structure is also called the voice box?
A) Trachea
B) Pharynx
C) Larynx ✅
D) Epiglottis Explanation: The larynx contains the vocal cords and produces sound.
Which structure covers the trachea during swallowing?
A) Uvula
B) Epiglottis ✅
C) Tongue
D) Soft palate Explanation: The epiglottis prevents food from entering the windpipe.
Which gas is necessary for cellular respiration?
A) Nitrogen
B) Carbon dioxide
C) Oxygen ✅
D) Helium Explanation: Oxygen is required to break down glucose for energy.
The windpipe is also known as the:
A) Larynx
B) Trachea ✅
C) Pharynx
D) Bronchi Explanation: Trachea is the medical term for windpipe.
Which lung is slightly smaller to accommodate the heart?
A) Right lung
B) Left lung ✅
C) Both are equal
D) None Explanation: The left lung has a cardiac notch to accommodate the heart.
Breathing rate is controlled by which part of the brain?
A) Cerebellum
B) Cerebrum
C) Medulla oblongata ✅
D) Thalamus Explanation: The medulla regulates involuntary breathing.
Respiration is essential for:
A) Photosynthesis
B) Energy production ✅
C) Digestion
D) Excretion Explanation: Respiration releases energy needed for body functions.
Which part of the respiratory tract warms and moistens the air?
A) Alveoli
B) Nasal cavity ✅
C) Bronchi
D) Pharynx Explanation: The nasal passage warms and humidifies incoming air.
What happens to the diaphragm when we inhale?
A) It relaxes
B) It contracts ✅
C) It remains still
D) It thickens Explanation: The diaphragm contracts and flattens to expand lung volume.
🟡 Moderate Level (21–40)
What lines the respiratory tract to trap particles and microbes?
A) Mucus and cilia ✅
B) Capillaries
C) Alveoli
D) Cartilage Explanation: Mucus traps particles, and cilia move them out of the tract.
How many lobes are in the right lung?
A) 1
B) 2
C) 3 ✅
D) 4 Explanation: The right lung has 3 lobes; the left has 2.
What is the function of surfactant in the lungs?
A) Increase friction
B) Reduce surface tension ✅
C) Absorb oxygen
D) Trap dust Explanation: Surfactant prevents alveoli from collapsing by reducing surface tension.
Where is the respiratory center located?
A) Hypothalamus
B) Medulla oblongata ✅
C) Cerebellum
D) Pituitary Explanation: The medulla oblongata regulates the rhythm of breathing.
Which phase of respiration involves the intake of air?
A) Exhalation
B) Inhalation ✅
C) Diffusion
D) Osmosis Explanation: Inhalation is the process of drawing air into the lungs.
What part of the pharynx conducts air to the larynx?
A) Nasopharynx
B) Oropharynx
C) Laryngopharynx ✅
D) Hypopharynx Explanation: Laryngopharynx is the lowest part of the pharynx and directs air into the larynx.
The exchange of gases in the lungs is facilitated by:
A) Active transport
B) Diffusion ✅
C) Osmosis
D) Filtration Explanation: Gases move across alveolar membranes by passive diffusion.
What type of epithelial tissue lines the alveoli?
A) Columnar
B) Cuboidal
C) Squamous ✅
D) Transitional Explanation: Alveoli are lined by simple squamous epithelium for rapid gas exchange.
What is tidal volume?
A) Total lung volume
B) Volume during forced inhalation
C) Air exchanged in normal breathing ✅
D) Residual air left after exhalation Explanation: Tidal volume is the air exchanged during normal, quiet breathing.
What is the function of pleural fluid?
A) Transport gases
B) Aid blood flow
C) Lubricate lungs ✅
D) Trap bacteria Explanation: Pleural fluid reduces friction between lung surfaces and chest wall.
Which condition involves inflammation of bronchi?
A) Asthma
B) Pneumonia
C) Bronchitis ✅
D) Emphysema Explanation: Bronchitis is the inflammation of the bronchial tubes.
What is the primary stimulus for breathing?
A) Low oxygen
B) High carbon dioxide ✅
C) Low blood pressure
D) High pH Explanation: Rising CO₂ levels in the blood stimulate the respiratory center.
Which muscle group assists the diaphragm during deep breathing?
A) Abdominal muscles ✅
B) Quadriceps
C) Biceps
D) Gluteals Explanation: Abdominal muscles help forcefully expel air during deep or forced breathing.
Vital capacity is the sum of:
A) Residual and tidal volume
B) Tidal, inspiratory, and expiratory reserve volumes ✅
C) Total and residual volume
D) None of the above Explanation: Vital capacity includes all air that can be inhaled and exhaled.
What is the main function of the respiratory system?
A) Produce energy
B) Transport nutrients
C) Exchange gases ✅
D) Filter blood Explanation: The system exchanges oxygen and carbon dioxide with the environment.
What percentage of oxygen is transported in hemoglobin?
A) 98% ✅
B) 75%
C) 50%
D) 25% Explanation: Most oxygen in blood is carried bound to hemoglobin.
Carbon monoxide is dangerous because it:
A) Blocks oxygen entry
B) Binds to hemoglobin tightly ✅
C) Causes lung infection
D) Destroys alveoli Explanation: CO binds to hemoglobin more strongly than oxygen, reducing oxygen delivery.
What is residual volume?
A) Extra air inhaled
B) Air exhaled forcibly
C) Air remaining after full exhalation ✅
D) Air used in speech Explanation: Residual volume is the air that stays in lungs after maximum exhalation.
Which disease destroys alveoli and reduces surface area for gas exchange?
A) Asthma
B) Tuberculosis
C) Emphysema ✅
D) Bronchitis Explanation: Emphysema breaks down alveoli walls, impairing gas exchange.
Hyperventilation causes:
A) Decreased CO₂ levels ✅
B) Oxygen depletion
C) Lung collapse
D) Alkalosis prevention Explanation: Rapid breathing removes too much CO₂, leading to respiratory alkalosis.
🔴 Hard Level (41–50)
Bohr effect describes the relationship between:
A) CO₂ and oxygen release from hemoglobin ✅
B) Oxygen and pH
C) CO₂ and pH only
D) pH and bicarbonate Explanation: Bohr effect shows that higher CO₂ lowers hemoglobin’s oxygen affinity.
Carbaminohemoglobin forms when:
A) CO₂ binds with water
B) CO₂ binds with hemoglobin ✅
C) Oxygen binds with hemoglobin
D) CO binds with hemoglobin Explanation: CO₂ binds to globin part of hemoglobin forming carbaminohemoglobin.
What enzyme helps convert CO₂ into bicarbonate in RBCs?
A) Trypsin
B) Catalase
C) Carbonic anhydrase ✅
D) Pepsin Explanation: Carbonic anhydrase facilitates rapid conversion of CO₂ into bicarbonate.
Oxygen-hemoglobin dissociation curve shifts right due to:
A) Low CO₂
B) High pH
C) Low temperature
D) High CO₂ and temperature ✅ Explanation: High CO₂, temperature, and low pH decrease hemoglobin’s oxygen affinity.
Which part of the respiratory system has the smallest cross-sectional area?
A) Trachea ✅
B) Bronchi
C) Bronchioles
D) Alveoli Explanation: The trachea is a single tube; total alveolar surface is much larger.
In which form is most CO₂ transported in the blood?
A) Dissolved in plasma
B) Carbaminohemoglobin
C) Bicarbonate ion ✅
D) CO₂ gas Explanation: ~70% of CO₂ is transported as bicarbonate ions.
Which law explains gas diffusion based on pressure gradient?
A) Boyle’s law
B) Charles’ law
C) Dalton’s law
D) Henry’s law ✅ Explanation: Henry’s law governs gas diffusion based on partial pressure and solubility.
Oxygen is primarily carried in the blood by:
A) Plasma
B) Hemoglobin ✅
C) White blood cells
D) Platelets Explanation: Hemoglobin binds to and transports oxygen in RBCs.
The respiratory membrane consists of:
A) Alveolar and capillary walls ✅
B) Bronchioles
C) Cartilage and mucus
D) Cilia and goblet cells Explanation: The respiratory membrane is where alveolar and capillary walls meet for gas exchange.
Which condition results in difficulty exhaling air from the lungs?
A) Asthma ✅
B) Pneumonia
C) Tuberculosis
D) Pleuritis Explanation: Asthma causes airway narrowing, making exhalation difficult.