Science textbook solutions for Class 7 science Chapter 12 The Muscular System and Digestive System in Human Beings

1. There  are more than 600 muscles  in the human body. Muscles contribute almost 40% of the weight of a healthy  adult human body. 
2. There  are about 30 muscles in the human face. Our  eyes, mouth and nose are encircled  by small  muscles. 
3. Expressions like  happiness, sadness, fear are expressed by the movements  of these muscles of the face.  The study  of  muscles is called myology.  
4. Contraction is the basic property of muscles. The largest muscle of our body is in the thigh. The smallest muscle  is attached  to a bone in the ear, called  the stapes. 
5. Muscles of our body must be strong and efficient. Our diet must include proteins and carbohydrates in sufficient quantity for the proper growth and repair of  muscles. We must get regular exercise. 
6. Enzymes  are  substances secreted in the body  of  an organism, which bring about specific chemical  reactions. They act as catalysts. 

Question 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.​

Question 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.

Answer :
1) Cardiac muscles – b) we never feel tired.

2) Are brought about
by muscles – d) chewing movements of jaws.

3) Pepsin – e) enzyme of the gastric juice.

4) Cramps – c) uncontrolled and painful contraction of muscles.

5) Skeletal muscles – a) always function

Question 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.

Answer :
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. Kidneys play an important role in excretion.

Question 4: Give reasons.
1) Food becomes acidic in the stomach.
Answer : The digestive juice secreted by the gastric glands present on the stomach walls is called as gastric juice. The food that enters the stomach becomes acidic on mixing with this gastric juice. The main components of gastric juice are hydrochloric acid, pepsinogen, mucus, and rennin.

2) Cardiac muscles are said to be involuntary muscles.
Answer : Cardiac muscles are said to be the involuntary muscles as they are not in our controls. Those muscles which are in ours controls are called as the voluntary muscles and those muscles which are not in ours controls are called as the Involuntary muscles. Cardiac muscles are the muscles of the hearts. We cannot stop them.

3) Intoxicating substances should not be consumed.
Answer : The intoxicating substances should not be consumed because of the given reasons. Explanation: When the intoxicating substances are consumed in a body, the mental and physical functions are hampered. They are a cause of effecting the heartbeat.

4) Your muscles should be strong and efficient.
Answer : Your muscles should be strong and efficient because –
– Muscles are soft tissue of body which primary functions as power source.
– Usually when we say muscles, it’s about skeletal muscles.
– Our movements are possible due to contractions of muscle.
– Muscles help us to maintain posture of the body & locomotion.
– Therefore, strong & efficient muscles are requirements for healthy well-being.

Question 5: Answer the following.
a) How many types of muscles are there? Which are those types?
Answer : Types of muscles 3 types Muscles in the human body

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?
Answer : One common cause of acid reflux disease is a stomach abnormality called a hiatal hernia. This occurs when the upper part of the stomach and LES move above the diaphragm, a muscle that separates your stomach from your chest. Normally, the diaphragm helps keep acid in our stomach.

c) Name the different types of teeth. What is the function of each type?
Answer : There are 4 types of teeth in the oral cavity: Incisors – The four front teeth in both the upper and lower jaws are called incisors. Their primary function is to cut food. The two incisors on either side of the midline are known as central incisors.

Incisors – The four front teeth in both the upper and lower jaws are called incisors.  Their primary function is to cut food.  The two incisors on either side of the midline are known as central incisors.

Canines – There are four canines in the oral cavity. Two in the maxillary arch and two in the mandibular area.  They are behind and adjacent to the lateral incisors.  Their main function is to tear food.

Premolars (Bicuspids) – These teeth are located behind and adjacent to the canines and are designed to crush food.  There are eight premolars in the oral cavity.

Molars – The most posterior teeth in the mouth are the molars.  They have broader and flatter surfaces with 4-5 cusps.  They are designed to grind food.

Question 6 : Sketch and label a diagram of the digestive system and describe it in your own words.
Answer : A human digestive system is a group of organs working together to convert food into energy and basic nutrients to feed the entire body. The food we take in is digested and utilized by our body and the unused parts of the food are defecated. Human digestive system is the sum of the gastrointestinal tract (GIT; also called alimentary canal) and accessory organs (tongue, liver, pancreas, etc). These two parts together help in digestion in humans.

The alimentary canal is the long tube through which the food that we eat is passed. It begins at the mouth (buccal or oral cavity), passes through the pharynx, esophagus or food pipe, stomach, small intestines, large intestines, rectum and finally ends at the anus. The food particles get digested gradually as they travel through various compartments of the alimentary canal. Accessory organs are organs which participate in the digestion process but are not actually a part of GIT. They stimulate the digestion by releasing certain enzymes.

Food begins its journey through the digestive system in the mouth, also known as the buccal cavity or the oral cavity. The mouth has many accessory organs such as the tongue, teeth, and salivary glands, which help in the digestion of food. Teeth grind the food into small pieces. Salivary glands secrete saliva which contains an enzyme called the salivary amylase. This enzyme breaks down starch content and moistens the food, before the tongue and other muscles push the food into the pharynx.

Mouth :  Digestion of food begins  in  the mouth.  Food is  chewed with the help of teeth into very small pieces.

Stomach :  The  large  sac-like  part  of the alimentary canal is called  the stomach. The gastric glands of stomach secrete gastric juice. Food that has  entered stomach  is churned. Three components of gastric  juice,  namely, hydrochloric acid, pepsin and mucus are mixed with food here and  it becomes acidic.

Small intestine :  The small intestine is about 6m long. Most of the digestion and  absorption of food takes place here.

Large intestine :  The large intestine  is about 1.5m long. Only water is absorbed in the large  intestine.  A  small part called the ‘appendix’ is attached to the first part of large intestine.

Salivary glands  :  Saliva is produced in the salivary glands in  the mouth  cavity.

Oesophagus :   It  is a tube leading from the pharynx to the stomach.  It pushes the food towards the stomach.

# let’s recall 
1. What is meant  by ‘organ system’ ? 
Answer : In biology, an organ system is a group of organs that work together to perform one or more functions. Each does a particular job in the body, and is made up of certain tissues.

2. How are the bones in our body joined to each other ?
Answer : Bones can move because of the way they are joined together. The place where two or more bones come together is called a joint. The bones at a joint are held together by strong bands of tissue called ligaments which allow the bones to move.

3. What is  the mutual relationship between muscles and  bones ?
Answer : Only skeletal muscles work with bones and muscles keep bones in place and also play a role in the movement of bones. To allow motion, different bones are connected by joints. A skeletal muscle may attach a bone to another bone (often across a joint) or a bone to another structure, such as skin.

4. Which parts of our body are made up only of muscles ?
Answer : Heart, digestive organs, tongue and blood vessels are made up of only muscles. Apart from that, bladder, uterus, lungs and digestive tract are also made with muscles only. But according to the medical studies, skeletal muscles are the only body part which is solely made with muscle.

5. How do muscles perform their  functions ?
Answer : The main function of the muscular system is movement. Muscles are the only tissue in the body that has the ability to contract and therefore move the other parts of the body. Related to the function of movement is the muscular system’s second function: the maintenance of posture and body position.

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