Grade Six Science
Hello Boys and Girls,
How are you getting along with your work? Keep revising and paying attention to your teachers.
This week we will be looking at another system of the body. We will be examining the Digestive System. The Digestive System is a very interesting system. For food to be of value to the body it must be digested. For food to be of value to the body it must be digested. What is digestion? Can you tell? Digestion is really the breaking down of food into smaller and simpler substances which can be used by the body. Food must first enter the mouth and be cut into smaller pieces, then broken down into simpler substances, before it could be of value to the body.
Let us examine the food canal. It is also called the Alimentary Canal.
The alimentary canal is really quite a long tube. It begins at the mouth and ends at the anus. This tube is a muscular one quite a few feet long. Can you imagine that? It is curled up in some parts and straight in others. It is thin in some parts and fat in others. Look very carefully at the diagram which is nearby. It shows what your alimentary canal looks like. Do you see how it takes on different shapes and sizes at various points?
Look at the diagram and read the names given to each part. Try to remember as many parts as you can.
Point to the:
● ● ● ● ● ● ● ● ● mouth gullet stomach pancreas liver
Small intestines large intestines rectum anus
Can you identify the appendix?
In the mouth the food is chewed and mixed with saliva. Why should we chew our food? Chewing reduces the food into suitable sizes for swallowing. Chewing also exposes more of the food to saliva. Do you know that saliva contains certain juices? Oh, yes, and these juices start to break down certain kinds of food into a simpler substance. So take time to chew. Chew your food well!
Next the food is swallowed and passed down the gullet. Note well - no digestion takes place here. Muscles in the walls of the gullet help to push the food down. Which do you think would go down faster, solids or liquids? Do you feel the food going down?
Muscles in the walls of the gullet help to push the food down. Have you found out where it goes to? That’s right, it enters the stomach. Locate where your stomach is. Touch it. What does your stomach look like when you have just had a hearty meal (especially those who love to eat)? The stomach is like a bag. It is filled out when there is a lot of food inside and ‘flat’ when it is empty.
The food remains for some time in the stomach. (Do you how many hours it stays there? If you don’t, find out.) The walls of the stomach are very muscular, and so help to mix the food. Inside the stomach, juices from the walls help to digest the food even further. When the digestion there is complete, the food is very soft and like a thick liquid. It then goes into the small intestine where the food may be even further digested (broken down). The walls of the small intestine then allows this digested food to be absorbed into the bloodstream. Through this blood it reaches all the organs and other parts of the body.
That was quite an exhausting trip, wasn’t it? The food that we eat certainly does quite a bit of travelling!
Let’s rest for a short while and do a word search, then answer a few questions afterwards.
Try to find the following words: stomach, digestion, gullet, mouth, oesophagus, digest, food, muscular, juices, alimentary, canal, intestine, anus, large
What was your score?
Did you get all 14? Then excellent. If you missed a couple, that’s still very good. If you got between 9 and 11 of the words, that’s also good. If you found fewer, then try harder.
Questions: 1. The alimentary canal begins at the _____________ and ends at the _______________. own words.
2. No digestion takes place in the (stomach, gullet, mouth)
3. What is digestion? Explain in your 4. Why is digestion important?
The Excretory System
Good, now let us begin to examine another system of the body. We will begin our study of the Excretory System. What is the Excretory System all about?
Let us now examine the Excretory System. It is yet another important system of the body.
‘Excretory’ comes from the word excretion. What is excretion? (If you do not know, find out.) Excretion is the process which helps to get rid of unwanted material produced by the body. The body has a special system for getting rid of waste products. Of course you know; it is the Excretory System. The Excretory System is so very important to our body. Can you imagine what would happen if the body does not get rid of its waste materials? That’s right, you would become ill. The body would shut down and you could eventually die.
Do you know which organs are the main organs of excretion? The main organs of excretion are the kidneys. Look at the labelled diagram below of a kidney.
The kidney is shaped like a bean. (Did you liken it to any other object?) It is reddish in colour and is found toward the back of the abdominal cavity, a bit above the waist. If you put your hands on your waist, your kidneys are situated just where your thumbs rest. You will notice that we mentioned kidneys (plural). We have two kidneys, left and right. You will see them in the diagram of the Excretory System.
The kidneys form a part of the urinary system. Each kidney is composed of thousands of tiny tubes called nephrons. It is in these tiny tubes that urine is produced.
We will continue our discussion next week, boys and girls. Until then, goodbye.