Chapter 21 - Busy at Work - our Internal Organs
1. What’s the solution ?
A person has fainted and a crowd of people has surrounded him.
Ans: If a person has fainted and a large group of people have gathered around him, we must first clear out the gathering in order to provide the person with enough oxygen. If the person is still unconscious, mouth-to-mouth respiration can be used.
2. Use your brain power !
(a) Why do we sometimes choke suddenly while eating?
Ans: After swallowing, the food we chew in our mouth enters the oesophagus. The upper ends of both the oesophagus and the windpipe open in the throat next to each other. When we swallow the food in a hurry while eating, sometimes the food suddenly enters the windpipe, causing us to suddenly choke.
(b) How is the air that we inhale purified in our body?
Ans: The inner lining of the respiratory tract secretes a sticky substance called mucus. It also has hair-like structures called cilia. The air that we inhale is purified with the help of this mucus and cilia. The cilia filter the dust, smoke, microorganisms, etc., and these substances get entangled in the sticky mucus and stick to the inner lining of the nose. Sometimes the cilia push out these substances towards the nostrils, which are then blown out by sneezing. Thus, this is how the air that we inhale is purified.
3. Fill in the blanks.
(a) ……………. gas is transported to all parts of the body.
Ans: Oxygen
(b) The stomach is like a ……………. .
Ans: bag
4. Match the following.
| Group A | Group B |
|---|---|
(1) Lungs | (a) Circulation |
(2) Stomach | (b) Respiration |
(3) Heart | (c) Co-ordination |
(4) Brain | (d) Digestion |
Ans:
| Group A | Group B |
|---|---|
(1) Lungs | (b) Respiration |
(2) Stomach | (d) Digestion |
(3) Heart | (a) Circulation |
(4) Brain | (c) Co-ordination |
5. Answer the following questions
(a) Name the systems that carry out the different functions of the body.
Ans: The systems that carry out the different functions of the body are the digestive system, respiratory system, circulatory system, excretory system, nervous system, and skeletal system.
(b) Describe how the exchange of oxygen and carbon dioxide gases takes place in the lungs.
Ans:
(i) In the lungs, gaseous exchange occurs through alveoli and blood capillaries.
(ii) The oxygen inhaled through the air in the lungs moves from the alveoli to the blood in the capillaries through the process of diffusion as the oxygen concentration is high in the alveoli and low in the blood capillaries.
(iii) Similarly, carbon dioxide from the blood capillaries moves to the alveoli in the lungs and is released into the air through exhalation.
(iv) This occurs because the carbon dioxide concentration is high in the blood capillaries and low in the alveoli.
(c) Why do we call saliva a digestive juice?
Ans: Saliva is a liquid secreted by the salivary glands present in the cavity of the mouth. It helps food change into a soft, moist ball called a bolus that is easy to swallow and digest. Therefore, saliva is called digestive juice.
6. Choose the appropriate word from the brackets.
(circulation, trachea, diaphragm)
(a) Respiration takes place because of its up and down movement.
Ans: diaphragm
(b) The process of keeping the blood flowing continuously throughout the body.
Ans: circulation
(c) Air that enters through the nose passes into this tube.
Ans: trachea