Class 9 Respiratory System Mock Test (ICSE)

Topics in Respiratory System

• Pathway of air into the body
• Mechanics of breathing
• Oxygen debt and lactic acid
• Second wind
• Vital capacity and tidal volume
• Benefits of exercise on the respiratory system

Respiratory System practice questions with answers

1. Q1Multiple choice·1 mark
   What physiological phenomenon is experienced as a sudden feeling of relief, ease of breathing, and disappearance of breathlessness during prolonged exercise?

   1. (a)Tidal volume
   2. (b)Vital capacity
   3. (c)Oxygen debt
   4. (d)Second wind
   Show answer and step marks

   1. Correct option: (d)+1

   Answer: (d)
2. Q2Multiple choice·1 mark
   What is the normal volume of air inspired or expired during a single, normal, quiet breath in an average adult?

   1. (a)$3500\text{ mL}$
   2. (b)$1000\text{ mL}$
   3. (c)$4500\text{ mL}$
   4. (d)$500\text{ mL}$
   Show answer and step marks

   1. Correct option: (d)+1

   Answer: (d)
3. Q3Multiple choice·1 mark
   The accumulation of which substance in the skeletal muscles during heavy and strenuous exercise leads to muscular fatigue and cramps?

   1. (a)Lactic acid
   2. (b)Carbon dioxide
   3. (c)Ethanol
   4. (d)Pyruvic acid
   Show answer and step marks

   1. Correct option: (a)+1

   Answer: (a)
4. Q4Multiple choice·1 mark
   During inhalation (inspiration), what change occurs in the diaphragm and the thoracic cavity?

   1. (a)Diaphragm contracts and arches upward; thoracic volume increases.
   2. (b)Diaphragm contracts and flattens; thoracic volume increases.
   3. (c)Diaphragm relaxes and flattens; thoracic volume decreases.
   4. (d)Diaphragm relaxes and arches upward; thoracic volume decreases.
   Show answer and step marks

   1. Correct option: (b)+1

   Answer: (b)
5. Q5Long answer·4 marks
   Trace the complete pathway of air from the external environment to the site of gaseous exchange in the human respiratory system. Explain the functional importance of any two key structures involved in this pathway.
   Show answer and step marks

   1. First part of the pathway: External nostrils $\rightarrow$ Nasal cavity $\rightarrow$ Pharynx $\rightarrow$ Larynx.+1
   2. Rest of the pathway: Larynx $\rightarrow$ Trachea $\rightarrow$ Bronchi $\rightarrow$ Bronchioles $\rightarrow$ Alveoli.+1
   3. First structure with its function, any one of: nasal cavity, whose hairs and mucus filter dust and germs and whose lining warms and moistens the air; pharynx, the common passage for air and food; larynx, with the epiglottis closing the windpipe during swallowing and the vocal cords producing voice; trachea, kept open by C-shaped cartilage rings, with cilia and mucus trapping dust; bronchi and bronchioles, which carry air to every part of the lungs; alveoli, thin-walled air sacs surrounded by capillaries where oxygen diffuses into the blood and carbon dioxide diffuses out; or any other valid structure and function.+1
   4. Second structure with its function, a different one from the same list.+1

   Answer: Pathway: external nostrils $\rightarrow$ nasal cavity $\rightarrow$ pharynx $\rightarrow$ larynx $\rightarrow$ trachea $\rightarrow$ bronchi $\rightarrow$ bronchioles $\rightarrow$ alveoli. Any two structures with functions, e.g. nasal cavity (filters, warms and moistens air), epiglottis/larynx (stops food entering the windpipe), trachea (cartilage rings keep it open), alveoli (site of gaseous exchange).
6. Q6Long answer·4 marks
   Trace the complete sequential pathway of air from the external nostrils to the alveoli in the human respiratory system. State one function each for: (a) Nasal hair and mucus, and (b) Epiglottis.
   Show answer and step marks

   1. Correct sequential pathway: External nostrils $\rightarrow$ Nasal cavity $\rightarrow$ Pharynx $\rightarrow$ Larynx $\rightarrow$ Trachea $\rightarrow$ Bronchi $\rightarrow$ Bronchioles $\rightarrow$ Alveoli.+2
   2. Function of nasal hair and mucus, any one of: they trap dust particles and germs from the inhaled air; the mucus moistens the incoming air; or any other valid function.+1
   3. Function of epiglottis: Acts as a flap-like valve that covers the windpipe (glottis) during swallowing to prevent food from entering the respiratory tract.+1

   Answer: Pathway: external nostrils $\rightarrow$ nasal cavity $\rightarrow$ pharynx $\rightarrow$ larynx $\rightarrow$ trachea $\rightarrow$ bronchi $\rightarrow$ bronchioles $\rightarrow$ alveoli. (a) Nasal hair and mucus trap dust and germs from the inhaled air (mucus also moistens it). (b) The epiglottis covers the glottis during swallowing so food does not enter the windpipe.

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