Std 7 Science Chapter 12 The Muscular & Digestive System in Human Beings – questions and answers

Exercise

1. Fill in the blanks with the right word from the brackets.
(a) The process of digestion starts from the mouth.
(b) Eyelids have voluntary muscles.
(c) Production of blood cells is not a function of the muscular system. 
(d) Muscles of the heart are cardiac muscles.
(e) Pushing forward the food that has been chewed is the function of the oesophagus.​

2. Find a match for me.

Group ‘A’ Group ‘B’
(1) Cardiac muscles (a) always function
(2) Are brought about by muscles

(b) we never feel tired.
(3) Pepsin (c) uncontrolled and painful contraction of muscles.
(4) Cramps (d) chewing movements of jaws.
(5) Skeletal muscles (e) enzyme of the gastric juice.

  Ans. 1 – b;    2 – d;    3 – e;    4 – c;  5 – a

3. Who is telling a lie ?

Organ Statement
1. Tongue My taste-buds can tell only a sweet taste.
2. Liver I am the largest gland in the body.
3. Large intestine I am 7.5 meter long.
4. Appendix Digestion is impossible without me.
5. Lung I play an important role in excretion.

Ans: The tongue, large intestine, appendix and lungs are lying.
1. Tongue can taste salt, sweet and bitter tastes.
2. Large intestine is 1.5 meter long.
3. Appendix is not required for digestion.
4. Lungs play an important role in breathing.

4. Give reasons.
(1) Food becomes acidic in the stomach.

Ans. The food gets mixed with hydrochloric acid present in the stomach and the food becomes acidic.

(2) Cardiac muscles are said to be involuntary muscles.
Ans. Cardiac muscles are present in the heart and they are not controlled by our will, they continuously cause our heart to relax and contract. Therefore cardiac muscles are said to be involuntary muscles.

(3) Intoxicating substances should not be consumed.

Ans. If we consume any intoxicating substances, the mouth, pharynx, alimentary canal and other organs of the digestive system cannot function properly. It causes problems like vomiting, nausea, and headache. Besides, tobacco particles stick to teeth, gums and skin of the mouth cavity and slowly cause injury to those parts resulting in their dysfunction. This causes swelling of the gums and pain when moving the jaws. The pharynx and intestine become inflamed and the condition further progresses into cancer leading to death.

(4) Your muscles should be strong and efficient.

Ans. The action of muscles is necessary for all kinds of movements – from the small movements of eyelids to those that demand great strength as when chopping wood with an axe. Therefore muscles should be strong in our body.

5. Answer the following.
(a) How many types of muscles are there? Which are those types?
Ans. There are three types of muscles:

1. Skeletal muscles : The two ends of each of these muscles are attached to two different bones. Examples of such muscles are muscles of the arms and legs. Their movements are voluntary. They are also responsible for holding the bones of the skeleton together and giving shape to our body.

2. Heart or cardiac muscles : These muscles bring about the contraction and relaxation (beating) of the heart. Their movement is involuntary. Cardiac muscles cause our heart to relax and contract continuously at a rate of about 70 times per minute.

3. Smooth muscles : These muscles are present in the internal organs other than the heart. For example, muscles of the stomach, intestine, blood vessels, uterus, etc. Their movements are involuntary and slow. Various vital functions of our body, of which we remain quite unaware, are carried out by these special muscles.

(b) What causes the problem of acidity? What is its effect on the body?
Ans. The gastric wall of the stomach secretes hydrochloric acid. If the level of hydrochloric  exceeds its normal level, it causes the problem of acidity.

The effects of acidity in the body are:

(i) burning sensation in the stomach

(ii) difficulty in swallowing

(iii) belching         

(iv) nausea

(v) sour taste in the mouth

(vi)indigestion

(c) Name the different types of teeth. What is the function of each type?

Ans: There are four types of teeth, namely, incisors, canines, pre-molars and molars.

1. Incisors: There are four incisors present in the front of the mouth. They are used for biting and cutting food.
2. Canines: There are two canines in each jaw that are used for tearing and piercing food.
3. Premolars:  There are four premolars in each jaw lie next to the canines. that are used for chewing and grinding food.
4. Molars: There are six molars in each jaw that lie next to the premolars at the end of the jaw, they are also used for chewing and grinding food.

6. Sketch and label a diagram of the digestive system and describe it in your own words.

Ans. The digestive system consists of the alimentary canal and digestive glands. The total length of alimentary canal is about 9 metres. Its main parts are the mouth, pharynx, oesophagus, stomach, small intestine, large intestine, rectum and anus. The salivary glands, liver and pancreas are the digestive glands connected to the alimentary canal.

Project :

1. Make charts about maintaining good health.

2. Design a power point presentation about the digestive system and present it in the class.

Extra Textual Questions:

Let’s recall.

What is meant by ‘organ system’?

Ans. An organ system is a group of organs that work together as a biological system to perform one or more functions. e.g. digestive system, respiratory system, circulatory system, etc

How are the bones in our body joined to each other?

Ans. Bones are joined to other bones by long, fibrous tissue called ligaments.

What happens to the food we eat, inside our body ? Does this food mix as it is with the blood ?

Ans. No, The food that we eat cannot be absorbed by the blood as it is. The various enzymes secreted by the different digestive organs mix with the food. The food is then broken down into soluble substance and absorbed by the blood. the insoluble substance of the food is thrown out of the body in the form of stools.

Can you tell ?

What is the mutual relationship between muscles and bones?

Muscles are firmly attached to bones by means of tendons. When muscles contract, there is movement at the joint and the bones move either nearer to or away from each other.

Are the muscles of the different organs in our body identical?

Ans. No, muscles of the different organs in our body are not identical.

How do muscles perform their functions ?

Ans. Muscles in our body always work in groups. When some muscles contract, other muscles of the same group, relax.

Use your brain power!

Which parts of our body are made up only of muscles?

Ans. The tongue, stomach, heart, lungs, etc are some of the parts of our body that are made only of muscles.

What would happen if : 1. The cardiac muscles do not move.

Ans. If the cardiac muscles do not move then our heart will not pump blood.

2. Food enters the stomach and the stomach muscles do not move.

Ans. If our stomach muscles do not move when food enters the stomach then the food will remain as it is and the food will not get digested.

During digestion, does all the food that we have eaten get converted into useful, nutritive substances ?

Ans. No, all the food that we have eaten does not get converted into nutritive substance. Some of the food gets converted into soluble substances and is absorbed by the blood the other insoluble food is thrown out of our body in the form of stools.

Which organs in our body have voluntary muscles and which ones have involuntary muscles? Find out and make a list of each type.

Voluntary MusclesInvoluntary Muscles
biceps, the triceps, the quadriceps, diaphragm, pectoral muscles, abdominals, hamstrings, etc.  the cardiac muscle and smooth muscle lining the intestinal tracts, blood vessels, urogenital tracts, respiratory tract, etc.

31st May is World No Tobacco Day and 7th April is World Health Day.

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