St. Lawrence School
Subject - Science
Class - 4
Chapter - 3 Human Body : Digestive and Excetory System
( Part - 1 )
Learn about
* Digestive system
* Healthy eating habits
Digestive System
The process by which food is broken down into a simpler form so that it can be easily taken in or absorbed by our body is called digestion. Many organs work together and help in the process of digestion. The mouth, food pipe, stomach, small and large intestine, liver, rectum, and anus are the main organs of the digestive system. Let us learn about them.
Mouth Digestion starts in the mouth. The teeth help to break down and chew food. The chewed food then mixes with a liquid, called saliva, produced in our mouth. It makes the food softer and easier to swallow. The tongue helps in the proper mixing of saliva with the food.
Food pipe The food pipe ( oesophagus ) passes the food from the mouth to the stomach.
Stomach Inside the stomach, the food is broken down further into smaller pieces by churning and with the help of chemicals called digestive juices.
Small intestine From the small intestine, the undigested food passes into the large intestine. The large intestine is a shorter but wider, tube - like structure, which collects the indigestible food from the small intestine. The large intestine absorbs water from this undigested food and forms waste products called faeces.
Rectum Rectum is the final part of the large intestine. Faeces are stored in the rectum for a short time before being passed out through anus. Anus Faeces are removed from the body through the anus.
Need for chewing food well, and for regular bowel movements
You must eat your food slowly and chew it well. Chewing breaks down the food into smaller particles. Digestion and carbohydrate starts in the mouth, where smaller particles of food mix saliva. Saliva contains enzymes that help in digestion. Mixing of food with saliva in the mouth also liquefies it patially, so that it becomes easier in digesting it.
If you do not chew your food properly, large food particles reach your stomach, which take longer in digestion by the body. So, digestion may not occur properly and nutrients from the food may not be released completely for absorption into the body.
Chewing food well and a healthy digestive system helps in formation of proper faeces. This leads to regular bowel movement. This is important as our body should get rid of the toxins and waste materials that are in our body, which prevents digestive disorders and helps us stay healthy. Need for Water
Drinking water is vital for life. It is especially important for our digestive system. Without sufficient water, absorption of food and nutrients in the intestine will not be proper and the digested food material will dry up in the intestine. As a result the bowel movement will not occur properlyb. This will lead to constipation and discomfort. Excretory System
The excretory system helps in removing wastes from our body. The process by which wastes get removed from our body is called excretion. The excretory system is made up of a pair of kidneys, a pair of ureters, a urinary bladder, and a urethra.
Kidneys Urine is formed inside the kidneys. Urine contains harmful substances that are formed inside our body.
Ureters Urine is transported from the kidneys to the urinary bladder through thin tubes called ureters.
Urinary bladder Urine is stored inside the urinary bladder.
Urethra Urine is released out of our body through the urethra. Healthy Eating Habits
Healthy eating habits lead to good digestion of food and proper excretion. This makes you healthy and strong. You must follow the healthy habits as listed below for this:
* You should was your hands properly both before and after eating food.
* Always eat from a clean plate.
* Always eat a balanced diet. Avoid eating junk food.
* You should eat slowly.
* You should chew your food well.
* You should drink sufficient amount of water daily.
* Do not drink a lot of water while eating. It will dilute the digestive juices.
* Eat food rich in fibre. This helps in good bowel movement. Some important points......
* The process by which food is broken down into a simpler form so that it can be
easily taken in or absorbed by our body is called digestion.
* The main organs of the digestive system are the mouth, food pipe, stomach,
small and large intestines, liver, rectum, and anus.
* The digestion begins in the mouth. The teeth inside the mouth help in the
breaking down and chewing of food. The chewed food then mixes with a liquid,
called saliva, present in the mouth.
* The food pipe or oesophagus helps to transfer the chewed food from the mouth
the stomach.
* Inside the stomach, food is broken down further into smaller pieces by churning
and with the help of digestive juices.
* From the stomach, food passes into the small intestine. It is a long and hollow tube - like structure where useful nutrients from the digested food get absorbed
into the blood.
* The liver produces digestive juices that help in the digestion of food.
* Urine is formed inside kidneys.
* Urine is transported from the kidneys to the urinary bladder through ureters.
* Urine is stored inside the urinary bladder.
* Urine is released out of our body through the urethra. Exercises......
A. Choose the correct option.
1. The food passes from the stomach to the...... during digestion.
a. stomach b. mouth c. blood vessels d. small intestine
2. This organ forms faeces.
a. liver b. stomach c. large intestine d. anus
3. This organ passes the faeces to the anus after storing it for some time.
a. anus b. rectum c. urethra d. urinary bladder
4. Urine is stored inside the......
a. urethra b. kidneys c. ureter d. urinary bladder
5. Urine is transported from the kidneys to the urinary bladder through......
a. ureters b. kidneys c. urethra d. urinary bladder
B. Choose the correct word to fill in the blanks.
1. From the mouth, the chewed food reaches the...... (stomach/brain).
2. The...... (mouth /stomach) secretes digestive juices that help in the
digestion of food.
3. The...... (excretory /circulatory) system helps in removing wastes from our body
4. Urine is formed inside the...... (kidneys /ureter).
C. Name the following.
1. A liquid that mixes with the food in the mouth - saliva
2. Another name for the food pipe - oesophagus
3. The organ system that help in removing wastes from our body - kidneys
4. The process by which wastes get removed from our body - excretory
5. The part of the body in which the process of digestion starts - mouth
6. The organs that receives food from the food pipe - stomach
7. The organ that produces digestive juices - liver
8. The organ in which digestion is completed - rectum
9. The organ where urine is formed - anus
10. The organ from which urine is released from our body - urethra
D. Write T for True andF for False.
1. We should wash our hands before eating. (T)
2. We should always eat food from a clean plate. (T)
3. We should eat too much of junk food. (F)
4. We should drink a lot of water. (T)
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