Class IV: Science [Ch-6 Digestion]

 Define the terms

1. Oesophagus- The long tube between the mouth and the stomach which forces food from the throat into the stomach.

2. Liver- A large organ located above and in front of the stomach that filters toxins from the blood, and makes bile which breaks down fats.

3.  Pancreas- An enzyme-producing gland that helps in the digestion of carbohydrates, fats, and proteins in the small intestine 

Answer in one line 

1. What is the digestive system?

Ans. The system of the body processes food and gets rid of waste.

2. What is the role played by cementum in our body.

Ans. The cementum provides attachment of the jawbone to the root of the tooth.

3. Write the name of the sensitive part of the tooth and what does it contain?

Ans. The pulp is the sensitive part of the tooth. It contains nerve endings and blood.

Answer in short

1. What are enamel and dentine?

Ans. i) Enamel- is the shiny and the hardest part of the tooth. It is made up of calcium.

ii) Dentine-  is the largest part of the tooth. It protects the pulp.

2. How are microbes useful to us?

Ans. Microbes are useful to us as-

i) Yeast is added to make bread and cakes fluffy.

ii) Curd is made by adding bacteria to milk.

3. How are tooth decay and cavity caused?

Ans. Bacteria change sugar present in food into acid that causes infections, resulting in tooth decay further causing acid and making a hole in the tooth called the cavity.

4. How do the small intestine and stomach help in digestion?

Ans. The stomach produces enzymes and acids that break down food into a simple form so it can pass to the small intestine and the small intestine absorb almost all the nutrients (carbohydrates, fats, proteins) and helps in digestion.

Answer in detail 

1. How can we look after our teeth?

Ans. We can look after our teeth in the following ways-

i) We should brush our teeth with florid toothpaste hence a day.

ii) We should have regular dental checks up.

iii) We should drink milk for strong and healthy teeth. 

2. What are the different types of teeth? 

i) Incisors-

•  The four front teeth in the upper jaw and the lower jaw.
•  They are 8 in number.
• Used for cutting and biting.

ii) Canines-

• Pointed and sharp teeth beside the incisors are called canines.
•  They are 4 in number.
• Used for tearing the food.

iii) Premolars-

• These are bigger, stronger, and have ridges.
•  They are 8 in number.
• Used for crushing and grinding food.

iv) Molars-

• They are wider and stronger.
•  They are 8 in number.
• Used for grinding the food.

v) the Third molar-

• The last teeth are the wisdom teeth.
• They are also called third molars.
• They are 4 in number.

Give reason

1. Why it is necessary to chew food properly before swallowing it.

Ans. It is necessary to chew the food so that food becomes soft and mixed properly with saliva for better digestion. 

2. Why is it necessary to wash fruits before eating them?

Ans. To remove germs.

3. Varun brushes his teeth after eating a sugar snack. Does he do the right things give a reason?

Ans. It is suitable to rinse or brush after eating a sugary snack as it avoids the risk of tooth decay.

Diagram

Structure of a tooth