Download 2-digestive system - natural science 3rd year

NUTRITION AND HEALTH
Like all living things, we have three life processes: interaction, nutrition and
reporduction. We use different body systems for nutrition. In this unit you will
learn how body systems work together to provide the nutrients and the oxygen
our body needs.
1-NUTRITION
It is the process of taking in food and turning it into energy. Food contains the
nutrients we need to live and grow. When we eat, we take these nutrients into
our body and transform them into material that helps us grow, repairs damaged
cells and gives us energy.
2-DIGESTIVE SYSTEM
Our digestive system breaks food down into small substances called nutrients.
All our organs and muscles need these nutrients. Once the digestive system
has extracted the nutrients, it gets rid of waste.
2.1.ORGANS OF OUR DIGESTIVE SYSTEM
The digestive system is made up of six organs, they are the:
1. Mouth: food enters our body through our mouth. Here food is broken up by
the teeth and mixed with saliva by the tongue.
2. Oesophagus: a long tube between our mouth and the stomach. Food goes
down this tube into the stomach.
3. Stomach: it is like a bag and it secretes gastric juice, the stomach receives
food from the oesophagus and mixes it with this gastric juice.
4. Intestine: a long tube. It is composed of two parts:
- Small intestine: it is about seven metres long. There are lots of blood vessels.
Nutrients pass into the blood here.
- Large intestine: it is about one metre and a half long. It takes the bad
substances from our body. Water goes out into the body and the waste
becomes harder.
5. Anus: it is at the end of the large intestine. Faeces are eliminated through the
anus.
DID YOU KNOW that water, minerals and vitamins pass
into the blood without being digested because they are
very small. Digestion takes about 2 hours.
3-THE EXCRETORY SYSTEM
Excretory system helps our body to get rid of excess water and waste products.
We clean our blood and eliminate waste from our body.
3.1. ORGANS OF THE EXCRETORY SYSTEM
1. Kidneys: when the blood goes through here, excess water and waste
products are dicreased and trasnsformed into urine. The urine goes into the
bladder.
2. Ureters: the urine goes down these tubes to the bladder.
3. Bladder: the urine is stored in this bag. When it is fullit sends a message to
the brain.
4. Urethra: the urine leaves the body through this tube.
4-THE CIRCULATORY SYSTEM
Circulatory system works all the time, day and night. It is a transport system that
takes blood to the parts of the body. Blood is a very important red liquid in our
body. It carries oxygen and nutrients to different parts of the body. Blood goes
around the body: circulation. The main organ of this system is
1. Heart: an involuntary muscle. It is a hollow muscle that pumps blood around
our body. It is between our two lungs.
Blood circulates around our body inside
2. Blood vessels: a network that takes the blood around the body: There three
types:
a) Arteries: take the blood from our heart to the rest of the body.
b) Veins: return the blood back to our heart.
c) Capillaries: connect the veins and arteries.
Blood has a watery liquid called plasma. The plasma carries nutrients and also
red cells, white cells and platelets.
5-RESPIRATORY SYSTEM
All our organs and muscles need oxygen to function. Blood picks up the oxygen
our body needs from the air into the lungs. when we breathe, the respiratory
system takes oxygen and eliminates carbon dioxide.
5.1. ORGANS OF RESPIRATORY SYSTEM
1. Nose: has two nostrils with little hairs to stop foreign objects. They are
narrow at the back.
2. Windpipe: divides into two tubes that go into the lungs.The tubes are called
the bronchi.
3. Lungs: are like two big sacks. They are like a sponge. They are made up of
lots of little bags called alveoli. The air goes into the alveoli.
6-HEALTH AND NUTRITION
We are what we eat. Our diets need to be healthy and balanced. It is
necessary to eat a variety of food with different nutrients: minerals and vitamins
(vegetables and fruit), carbohydrates (give energy), proteins (help us grow and
have strong bones and teeth) and fats (extra energy for when we need it). Avoid
eating salty and sugary foods. drink lots of water.
To have a healthy lifestyle:
a) Be active: do exercice at least three times a week.
b) Sleep: sleep at least nine hours a night.
c) Limit screen time: try not to spend more than two hours a day.
d) Protect your body from bacteria and viruses by:
-washing your hands and brush your teeth.