Part 1: Respiratory System in Humans (Anatomy & Structures) – 25 MCQs

Q1. Which of the following is the correct sequence of structures in the human respiratory tract?

A. Nostrils → Trachea → Pharynx → Bronchi → Lungs
B. Nostrils → Pharynx → Larynx → Trachea → Bronchi → Bronchioles → Alveoli
C. Pharynx → Nostrils → Trachea → Larynx → Lungs
D. Nostrils → Larynx → Pharynx → Trachea → Lungs

Answer: B

Explanation:

A. Incorrect: Pharynx comes immediately after nostrils, not trachea.
B. Correct: This is the correct anatomical sequence.
C. Incorrect: Nostrils are before pharynx.
D. Incorrect: Larynx comes after pharynx, not before.

Q2. Which of the following prevents food from entering the respiratory tract during swallowing?

A. Glottis
B. Epiglottis
C. Uvula
D. Vocal cords

Answer: B

Explanation:

A. Incorrect: Glottis is the opening of larynx.
B. Correct: Epiglottis acts as a flap covering glottis while swallowing.
C. Incorrect: Uvula prevents food entry into nasal cavity.
D. Incorrect: Vocal cords produce sound, not prevent food entry.

Q3. The functional units of lungs where gaseous exchange occurs are:

A. Bronchi
B. Bronchioles
C. Alveoli
D. Pleura

Answer: C

Explanation:

A. Incorrect: Bronchi only conduct air.
B. Incorrect: Bronchioles are smaller airways but not exchange units.
C. Correct: Alveoli provide large surface area for gas exchange.
D. Incorrect: Pleura is a covering membrane.

Q4. Which cartilage prevents collapse of the trachea?

A. Elastic cartilage
B. C-shaped hyaline cartilage rings
C. Costal cartilage
D. Fibrocartilage

Answer: B

Explanation:

A. Incorrect: Elastic cartilage is in ear.
B. Correct: Trachea has 16–20 C-shaped hyaline cartilage rings.
C. Incorrect: Costal cartilage connects ribs.
D. Incorrect: Fibrocartilage is in intervertebral discs.

Q5. Which structure is called the “voice box”?

A. Pharynx
B. Larynx
C. Trachea
D. Epiglottis

Answer: B

Explanation:

A. Incorrect: Pharynx is a common food and air passage.
B. Correct: Larynx houses vocal cords, hence voice box.
C. Incorrect: Trachea is the windpipe.
D. Incorrect: Epiglottis is a flap, not voice box.

Q6. The lungs are enclosed in a double membrane called:

A. Peritoneum
B. Pericardium
C. Pleura
D. Endothelium

Answer: C

Explanation:

A. Incorrect: Peritoneum surrounds abdominal cavity.
B. Incorrect: Pericardium surrounds heart.
C. Correct: Pleura is the double-layered membrane of lungs.
D. Incorrect: Endothelium lines blood vessels.

Q7. The left lung of humans has:

A. 3 lobes
B. 2 lobes
C. 4 lobes
D. 1 lobe

Answer: B

Explanation:

A. Incorrect: Right lung has 3 lobes.
B. Correct: Left lung has 2 lobes to accommodate heart.
C. Incorrect: No lung has 4 lobes.
D. Incorrect: Not single lobe.

Q8. The right lung of humans has:

A. 2 lobes
B. 3 lobes
C. 4 lobes
D. 1 lobe

Answer: B

Explanation:

A. Incorrect: Right lung has more lobes.
B. Correct: Right lung has 3 lobes.
C. Incorrect: No 4 lobes.
D. Incorrect: Not single lobe.

Q9. Which part of respiratory tract is lined with ciliated epithelium and mucus to filter air?

A. Trachea
B. Alveoli
C. Pleura
D. Diaphragm

Answer: A

Explanation:

A. Correct: Trachea has ciliated columnar epithelium with mucus.
B. Incorrect: Alveoli have simple squamous epithelium.
C. Incorrect: Pleura is a covering, not lining with cilia.
D. Incorrect: Diaphragm is muscular, not epithelial.

Q10. Which structure marks the beginning of the lower respiratory tract?

A. Pharynx
B. Larynx
C. Nasal cavity
D. Trachea

Answer: B

Explanation:

A. Incorrect: Pharynx is part of upper respiratory tract.
B. Correct: Larynx marks beginning of lower respiratory tract.
C. Incorrect: Nasal cavity is upper part.
D. Incorrect: Trachea is lower, but not the beginning.

Q11. Which of the following is NOT part of the conducting zone of the respiratory system?

A. Trachea
B. Bronchi
C. Bronchioles
D. Alveoli

Answer: D

Explanation:

A. Incorrect: Trachea conducts air.
B. Incorrect: Bronchi conduct air.
C. Incorrect: Bronchioles conduct air.
D. Correct: Alveoli are exchange zone, not conducting.

Q12. Gas exchange between alveoli and capillaries occurs by:

A. Active transport
B. Facilitated diffusion
C. Simple diffusion
D. Osmosis

Answer: C

Explanation:

A. Incorrect: No ATP needed.
B. Incorrect: Carrier proteins not involved.
C. Correct: Diffusion down partial pressure gradients.
D. Incorrect: Osmosis is for water.

Q13. Which muscles are primarily involved in normal inspiration?

A. Internal intercostals
B. External intercostals and diaphragm
C. Abdominal muscles
D. Pectoral muscles

Answer: B

Explanation:

A. Incorrect: Internal intercostals aid in forced expiration.
B. Correct: External intercostals and diaphragm contract during inspiration.
C. Incorrect: Abdominal muscles help in forced expiration.
D. Incorrect: Pectorals not main respiratory muscles.

Q14. The space between two pleural membranes is called:

A. Pericardial cavity
B. Pleural cavity
C. Thoracic cavity
D. Peritoneal cavity

Answer: B

Explanation:

A. Incorrect: Pericardial cavity surrounds heart.
B. Correct: Pleural cavity between visceral and parietal pleura.
C. Incorrect: Thoracic cavity contains lungs, heart.
D. Incorrect: Peritoneal cavity surrounds abdominal organs.

Q15. Which structure acts as the primary site of air filtration in the respiratory system?

A. Trachea
B. Nasal cavity
C. Larynx
D. Bronchi

Answer: B

Explanation:

A. Incorrect: Trachea filters further, but not primary.
B. Correct: Nasal cavity filters with hairs and mucus.
C. Incorrect: Larynx is voice box.
D. Incorrect: Bronchi are lower passageways.

Q16. The larynx opens into the trachea through:

A. Glottis
B. Epiglottis
C. Uvula
D. Bronchi

Answer: A

Explanation:

A. Correct: Glottis is opening between vocal cords into trachea.
B. Incorrect: Epiglottis covers glottis.
C. Incorrect: Uvula prevents entry to nasopharynx.
D. Incorrect: Bronchi branch from trachea, not larynx.

Q17. The diaphragm separates:

A. Thoracic and abdominal cavities
B. Right and left lungs
C. Pleural and pericardial cavities
D. Nasal and oral cavities

Answer: A

Explanation:

A. Correct: Diaphragm separates thoracic and abdominal cavities.
B. Incorrect: Mediastinum separates lungs.
C. Incorrect: Pleura/pericardium are separate membranes.
D. Incorrect: Hard palate separates nasal and oral cavities.

Q18. The alveolar epithelium is formed of:

A. Ciliated epithelium
B. Simple squamous epithelium
C. Stratified squamous epithelium
D. Cuboidal epithelium

Answer: B

Explanation:

A. Incorrect: Ciliated epithelium lines trachea.
B. Correct: Alveoli are lined by thin squamous epithelium for gas exchange.
C. Incorrect: Stratified squamous in esophagus.
D. Incorrect: Cuboidal lines ducts, not alveoli.

Q19. Which of the following structures is also called the “windpipe”?

A. Larynx
B. Pharynx
C. Trachea
D. Bronchus

Answer: C

Explanation:

A. Incorrect: Larynx = voice box.
B. Incorrect: Pharynx = common food/air passage.
C. Correct: Trachea = windpipe.
D. Incorrect: Bronchus = tracheal branch.

Q20. Which structure is present only in mammals among respiratory systems?

A. Alveoli
B. Trachea
C. Bronchioles
D. Pharynx

Answer: A

Explanation:

A. Correct: Alveoli are mammalian adaptations for efficient gas exchange.
B. Incorrect: Trachea found in most vertebrates.
C. Incorrect: Bronchioles found in birds too.
D. Incorrect: Pharynx is common in many groups.

Q21. The primary function of nasal conchae is to:

A. Produce sound
B. Warm and humidify inhaled air
C. Store oxygen
D. Expel CO₂

Answer: B

Explanation:

A. Incorrect: Sound = vocal cords.
B. Correct: Conchae increase surface area, warm and humidify air.
C. Incorrect: No oxygen storage.
D. Incorrect: Expelling CO₂ is alveolar function.

Q22. The right primary bronchus is:

A. Longer and narrower than left
B. Shorter and wider than left
C. Equal in length and diameter
D. Absent

Answer: B

Explanation:

A. Incorrect: Right bronchus is not longer.
B. Correct: Right primary bronchus is shorter, wider, more vertical → foreign objects lodge here.
C. Incorrect: They differ.
D. Incorrect: Right bronchus exists.

Q23. The total number of alveoli in both lungs of an adult human is about:

A. 2 million
B. 20 million
C. 200 million
D. 300 million

Answer: D

Explanation:

A. Incorrect: Too few.
B. Incorrect: Still fewer.
C. Incorrect: Underestimate.
D. Correct: About 300 million alveoli in both lungs.

Q24. The respiratory membrane is extremely thin, about:

A. 1 mm
B. 0.1 mm
C. 0.5 µm
D. 10 µm

Answer: C

Explanation:

A. Incorrect: 1 mm is too thick.
B. Incorrect: 0.1 mm = 100 µm, too thick.
C. Correct: Respiratory membrane ~0.5 µm thick.
D. Incorrect: 10 µm thicker than actual.

Q25. Which of the following structures is common to both respiratory and digestive systems?

A. Trachea
B. Larynx
C. Pharynx
D. Esophagus

Answer: C

Explanation:

A. Incorrect: Trachea = respiratory only.
B. Incorrect: Larynx = respiratory only.
C. Correct: Pharynx conducts both food and air.
D. Incorrect: Esophagus = digestive only.

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Part 1: Respiratory System in Humans (Anatomy & Structures) – 25 MCQs