Modul 1

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Chapter 1 : Human Breathing Mechanism

Text of Modul 1


Parts Rib cage Nasal cavity Intercostal muscle Diaphragm Alveolus

Function Protects the lungs To warm, moisten and filter fine particles like dust Raises and lowers the rib cage during breathing Changes the air pressure in the thoracic cavity by increasing and decreasing the thoracic volume. The place where the exchange of gases takes place

1. Breathing is a process during which our body:a) Takes in of oxygen INHALATION b) Lets out of carbon dioxide EXHALATION 2. Pathway of inhaled Nose Trachea Bronchus Bronchiole Alveolus




Concept Map

RESPIRATION Involve s Human respiratory system Consist s of Breathing organs - Ribs Diaphragm - Intercostal muscles Processes



Air taken in

Air taken out

Nasal cavity Caused by Trachea Bronchu ss Bronchiol e Alveolu sO2

Change in pressure

Situated in the lungs



OBJECTIVE QUESTIONS3 One of the waste products of respiration is A. Carbon dioxide 1 Figure 1 below shows a cross- section of the 9 Which of the following organs is not involved B. Carbon monoxide the respiratory system? human respiratory system. C. A Nitrogen Lungs dioxide B Nitrogen Ribs oxide D. C Diaphragm D Heart 10 - Thoracic cavity becomes bigger - Air pressure inside the lungs is lowered - Air is forced into the lungs in

4 The information above shows the process Figure 1 Which of the following represents P, Q, R and S? A B C D 6. Which of the following, represents the lung ? A P C R 2 B Q D S W - Alveolus 7. What happens to the diaphragm during inhalation? X - Bronchiole Y - Bronchus A It curves and moves upwards Z and - moves Trachea B It relaxes upwards 1downwards C It contracts and Table moves D table It curves The showsand the moves variousdownwards parts of the humanP Q R S Trachea Alveolus Bronchus Bronchiole Trachea Bronchus Alveolus Bronchiole Figure 3 Bronchus Alveolus Bronchiole Trachea Alveolus Trachea Bronchus Bronchiole

of.. A B C D digestion inhalation exhalation respiration

Figure 5 What takes place in the structure labelled S? A Exchange of gases for breathing A B Secretion of enzymes for food digestion C Production of oxygen for respiration D Production of new cells to replace dead cells 11



respiratory system. Which is the correct sequence for the flow of oxygen from the air to the lungs ? A. B. C. D. W W Z Z X Y X Y Y X Y X Z Z W W

C D Air is exhaled out of the lungs in this sequence A K, L, M, N Figure 2 B N, M, K, L 5 InC Figure M,2, Kwhich , L, N part is the trachea? D N, L, K, M

12 In the breathing mechanism, which action reduces the volume of the thoracic cavity? Figure 4 shows a model of the human A The outer intercostal muscles contract. respiratory system. Which of the following B The inner intercostal muscles contract. statements is not true when the rubber sheet C The diaphragm muscle contracts. Stopper is pulled downwards? D The outer rib cage moves upwards and A Pressure in the bell jar decreases. forwards. B Both balloons expand. C D Air enters into the balloons. Both balloons expand until they burst.

Figure 4


P Q13 Which of the following releases water R vapour into the air? I Respiration S II Transpiration III Photosynthesis A B C D 14 16

Rubber sheet I and II only I and III only II and III only I, II and IIIFigure 7 Figure 7 shows the breathing mechanism. At which of the points, A, B, C or D is the air pressure lowest? 17

Figure 6 Figure 6 shows a simple model of the thoracic cavity. Which of the following occurs when the diaphragm curves upwards? A Outer intercostal muscles contract. B Air from the atmosphere is inhaled into the lungs. C Diaphragm muscle contracts. D Air pressure in the thoracic cavity is higher than the atmospheric pressure. 15 Which of the following occurs when the outer intercostal muscles contract? I The ribs move upwards. II Inner intercostal muscles contract. III Diaphragm muscle contracts. IV Volume of the thoracic cavity decreases. A B C D I and II only I and III only II and IV only I, III and IV only

Figure 8 Figure 8 shows the air passage from the nose to structure X. What are the characteristics of structure X? I Moist surface II Thin-walled III Surrounded by a network of blood capillaries A B C D I and II only I and III only II and III only I, II and III

18 Which of the following correctly shows the contents of inhaled air and exhaled air? Gas I II III IV A B C Oxygen Carbon dioxide Nitrogen Water vapour I and II only III and IV only II, III and IV only Inhaled air 21 % 0.03 % 78 % A little Exhaled air 16 % 4% 78 % 50 %



I, II, III and IV

STRUCTURE QUESTIONS 1. Diagram 1 shows a part of the respiratory system. (a) Name the structures labelled P, Q and R


Diagram 1




(b) Draw lines to show the correct match between the structures and their description.P

A sheet of muscles which separates the thorax from the abdomen Tube supported by rings of cartilage


Space where air passes through Bones that form the rib cage to protect the lungs


Diagram 2 below shows the process of inhalation in the human breathing mechanism.


Diagram 2

(a) Following the path of the air in the diagram 2, state what happens to the following parts during inhalation. External intercostal muscles:



Thoracic cavity:


(b) Name three types of gases inhaled in during the process of inhalation.



Figure 1 Figure 1 shows the human respiratory system. (a) Name the structures X, Y and Z. (i) X: _____________________________________________________ (ii) Y : ____________________________________________________ (iii) Z : _____________________________________________________ (b) Name the gas that diffuses through the alveolus into the capillaries. _____________________________________________________ (c) What takes place at Z? _____________________________________________________ (d) Complete the flow chart below to show the sequence of air movement from the nose to the alveolus.


Oxygen + haemoglobin Oxyhaemoglobin

Oxygenated blood

Deoxygenated blood

Oxyhaemoglobin Decomposes Oxygen Diffuses into the cells 1. Oxygen in the inhaled air that is taken into the alveolus in the lungs will diffuse into the blood capillaries. 2. The alveolus is efficient in gaseous exchange because: a) it has a one-cell thick b) it has moist (this helps gas to dissolve) c) it is surrounded by a large network of blood capillaries d) it has millions of alveoli to increase its surface area. 3. In the blood oxygen will combine with the haemoglobin in the red blood cells to form oxyhaemoglobin. 4. When oxyhaemoglobin reaches the body tissues, it decomposes to release oxygen. The oxygen then diffuses into the cells. In the body cells, the oxygen is used for respiration. 5. Respiration is a food oxidation process in the body cells to release energy, carbon dioxide and water. Glucose + oxygen carbon + water + energy dioxide



ALVEOLUS Diffusion Red blood cell

Combines with oxygen

Breaks down into Products of digestion

A type of process



1 Alveolus is suitable for diffusion of gasesbecause it has I II III IV thin walls dry surface area large number of blood capillaries small surface area


6 Cell respiration can be represented by the 10 The oxidation of food in a cell during cell A I and II following word equation: respiration as shown in the diagram below B I and III will produce a Figure gas. 2 C II and III Glucose + J K + water + carbon dioxide D II and IV Figure 2 shows the alveolus and the blood What do J and K represent? vessels around it. Haemoglobin is 2 Figure \ 1 below shows the exchange of gases transported from blood vessel X to blood between J an alveolus and a blood K capillary. vessel Y. Which of the following pairs A Oxygen Food represents blood vessels X and Y? B Oxygen Energy X can Y The gas C Haemoglobin Amino acids A Pulmonary vein Pulmonary artery D Ribosomes Energy B A. Pulmonary Pulmonary vein turn lime artery water chalky. C B. Vena cava Aorta ignite a glowing splinter. D C. Aorta Vena cava be used for respiration. 7 How does oxygen in the alveolus enter the D. support combustion. blood? 5 11 A By osmosis B By reverse osmosis C By diffusion D By transpiration Figure 1 The exchange of gases between the alveolus and 8 Which of the characteristics help the the blood capillary isfollowing by alveolus absorb oxygen more efficiently? A diffusion Gas Y that enters the blood stream from the B transfusion alveolus is used by cells as shown above I the alveolus is always dry C convection in the process of II the alveolus has a large surface area D conduction III the alveolus has thin walls A. assilimation. Figure 3 IV blood capillaries that carry oxygen B. digestion. 3 Which of the following statements is true about surround the alveolus C. respiration. the oxidation of food that takes place in cells? Which of the following represents gases X D. Y breathing. I This process is called respiration. and ? A. I, is II, absorbed. and III only II Energy X Y B. I, III, and only III Water vapour isIV released in this process. 12 A The breathing process is important in order Carbon dioxide Oxygen C. II, III, and IV only to B Oxygen Carbon dioxide D. I, II, III, IV A I and II only the water vapour content in the CI lower Hydrogen Oxygen B I and III only D alveoli. Oxygen Hydrogen from the lungs transported to C 9 II