Frank Solutions for Chapter 19 Respiratory System Class 9 Biology ICSE


1. Define respiration. Why is respiration essential for life?
Respiration: It is a process of release of energy from food substances such as glucose and fats under the control of enzymes, to carry out life processes, by the living organisms. Respiration is essential for life as energy produced during this process is utilized by the organisms to carry out various biological activities.

2. Give the structure of nasal chamber.
Structure of nasal chamber:
The nasal chamber is divided into left and right chambers by nasal septum. Each chamber is divided into three regions–
  1. Vestibule: It is the anterior most part of nasal chambers bearing hairs which filters the dust particles.
  2. Respiratory region: It is rich in mucous glands and marked by nasal turbinates which traps the dust and humidify the air.
  3. Olfactory chamber: It is lined by olfactory epithelium which sense the smell.

3. What are turbinates? What are their functions?
Turbinates: The respiratory region of nasal chamber is marked by three nasal turbinates. These are Ethmoturbinate, nasoturbinate and maxilloturbinates.
Function of turbinates: It increases the surface area, so that dust particles can be removed and air become humidified.

4. What is Adam's apple?
Adam’s apple: It is a prominent elevation formed by the laminae of thyroid cartilage. It is more pronounced in male than female.

5. Give the structure of a trachea.
Structure of Trachea: It is a long thin air tube about 11cm long and 2.5 cm broad. Its wall is semi-transparent and composed of 4 layers-
  1. Mucosa
  2. Submucosa
  3. Cartilaginous layer
  4. Adventita
The trachea in the thoracic region bifurcates into short tubes called primary bronchi which enters into the lungs.

6. What is the function of lecithin film in the lungs?
The function of lecithin film in the lungs is to decrease the surface tension and keeps the alveoli open.

7. Give the differences between alveoli of an infant and an adult.
Alveoli of Infant Alveoli of Adult
1. Alveoli of infant is this and tubular. 1. Alveoli of adult is thick and sac- like

8. What is breathing? Discuss the function of diaphragm in the breathing.
Breathing: It is the physical process of taking in oxygen and giving out carbon dioxide. The function of diaphragm: It helps in breathing by contracting and relaxing thereby increase and decrease the volume of thoracic cavity. During inspiration diaphragm flattens while during expiration it becomes dome – shaped

9. Define the following:
(i) Cough Reflex
(ii) Sneez Reflex
(iii) Eupnea
(iv) Dyspnea
(v) Apnea
(i) Cough Reflex: It is a type of reflex whose stimulus is any foreign particle which results from deep inspiration followed by strong expiration that forcefully expel the air through the mouth.

(ii) Sneeze Reflex: It is a type of reflex whose stimulus is in the nasal passage which causes spasmodic contraction of expiratory muscles that forcefully expel the air through the nasal passage.

(iii) Eupnea: Eupnea is a normal breathing.

(iv) Dyspnea: A condition in which breathing is painful.

(v) Apnea: A condition in which no breathing takes place.

10. What is internal respiration?
Internal respiration: It is the transport of oxygen in the blood from the lungs to the cells and the transport of carbon dioxide from the tissue cells into the blood and to the lungs.

11. Discuss respiratory quotient (R.Q.).
Respiratory quotient (RQ): It is the ratio of CO2 output to O2 uptake. It is denoted by R.
R = Rate of CO2 output / Rate of O2 uptake
RQ for carbohydrate = 1.00
RQ for fat = 0.70
RQ for protein = 0.85

12. Name the following:
(i) Anterior most part of nasal chamber bearing hairs.
(ii) Sound producing organ.
(iii) Miniature lungs.
(iv) A film covering the alveoli of lungs and lowers the surface tension.
(v) High breathing rate.
(vi) Painful breathing.
(vii) No breathing.
(viii) Low breathing rate.
(ix) Body cavity in which lungs are situated.
(i) Vestibule
(ii) Larynx
(iii) Alveoli
(iv) Lecithin
(v) Hyperpnea
(vi) Dyspnea
(vii) Apnea
(viii) Hypopnea
(ix) Thoracic cavity

13. Complete the following statements by choosing the correct alternative from those given in brackets.
(i) The protective covering of the lung ______.(pericardium, pleura, renal fat)
(ii) Normal breathing is termed as ______. (eupnea, apnea, Dyspnea)
(iii) Tidal volume is ______. (eupnea, apnea, dyspnea)
(iv) R.Q. for fat is ______. (1200 cc, 500 cc, 5000 cc)
(v) Net gain of complete cellular respiration of carbohydrate ______. (2 ATP, 34 ATP, 38 ATP)
(i) Pleura
(ii) Eupnea
(iii) 500 cc
(iv) 0.70
(v) 38 ATP

14. Give the functions of the following:
(i) Larynx _______
(ii) Alveoli _______
(iii) Chonchae ______
(iv) Epiglottis _______
(v) Lecithin covering ______
(vi) Cartilaginous rings _______
(i) Larynx = To produce voice
(ii) Alveoli = To increase the surface area for exchange of gases.
(iii) Conchae = It is also called turbinate and its function is to increase the surface area so that the dust particles can be removed and air become humidified.
(iv) Epiglottis = It closes the glottis during swallowing of food.
(v) Lecithin covering = It lowers the surface tension and keeps the alveoli open.
(vi) Cartilaginous rings = It prevents the collapsing of trachea.

15. Note the relationship between first two words and suggest the suitable word for the fourth place.
(i) Lungs _____ Respiration, Alveoli _____.
(ii) Nasal Chamber _____ Accliamatization, Larynx ______.
(iii) Olfactory Chamber _____ small, Thoracic Cage _____.
(i) Alveoli – Gaseous exchange
(ii) Larynx – Sound production
(iii) Thoracic cage – Breathing

16. Label the diagram given below:

17. Every question has four options. Choose the correct answer:

(i) Covering of lung is called
(a) perichondrium
(b) pleural membrane
(c) pericardium
(d) peritoneum
(b) Pleural membrane

(ii) Sites of gaseous exchange in the lung is
(a) tracheoles
(b) alveoli
(c) bronchiole
(d) pulmonary chamber
(b) Alveoli

(iii) Larynx acids as
(a) sound box
(b) value of controlling air
(c) organ producing sound
(d) all the above
(d) All the above

(iv) During respiration, the diaphragm
(a) relaxed to become dome shaped
(b) Contracts and flattened
(c) expands
(d) shows no change
(d) shows no change

(v) Vital capacity of lungs in an average man is
(a) 500-1000 ml
(b) 1500-1800 ml
(c) 2000-2500 ml
(d) 3000-4500 ml
(d) 3000 – 4500 ml

(vi) Partial pressure of O2 in inspired and expired air is
(a) 40 and 95 mm Hg
(b) 100 and 95 mm Hg
(c) 158 and 40 mm Hg
(d) 158 and 116 mm Hg
(d) 158 and 116 mm Hg 
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