natural sciences 6 UNIT

2

What happens when we eat?

1. Mouth: The teeth crush the food and then mix it with saliva.

2. Esophagus: The food travels down the esophagus to the stomach.

3. Stomach: The food mixes with gastric juices.

4. Liver: It produces a liquid called bile that helps break down food.

5. Small intestine: Here the food mixes with bile from the liver. Nutrients are absorbed here and they pass into the blood.

6. Large intestine: Theundigested food is transformed into faeces.

7. Rectum: The faeces pass through it and leave the body through the anus.

What happens when we breathe?

Mouth and nose: air entersthe body through the mouthand nose.

Lungs: these two large bags are connected to the bronchi. The bronchi branch into millions of smaller tubes, or bronchioles, here in the lungs.

Bronchi: these two smaller tubes connect the trachea to the lungs.

Vocal cords: as air passes our vocal cords, they vibrate and enable us to speak.

Trachea: this long, rigid tube connects our mouth and nose to our two bronchi. Air travelsdown the trachea intothe bronchi.

How does the circulatory system work?

1. The heart acts like a pump. It has four chambers. The two upper ones are called the atria and the two lower ones are called ventricles. When blood enters the heart, it’s then pumped to the lungs. In the lungs, the red blood cells absorb oxygen. That oxygenated blood is pumped back into the heart. The heart then pumps the oxygenated blood around the body.

2. The blood vessels connect the heart to the rest of the body. There are two types: arteries and veins. Arteries carry a lot of oxygenated blood away from the lungs and then the heart. Veins carry small quantities of blood which contains carbon dioxide back to the lungs.

3. The blood containing carbon dioxide travels back to the heart. It’s pumped into the lungs again so that the red blood cells can absorb more oxygen.

What’s excretion?What happens when we go to the toilet?

1. Undigested food and waste pass through the small intestine. They still contain a lot of water. In the large intestine, most of the water is absorbed back into the body. The solid waste that remains forms solid lumps are called faeces.

2. They pass into the rectum, where they’re stored. Finally, they are expelled through the anus.

1. The blood passes through our kidneys. They filter the blood, removing extra water and waste, forming a liquid called urine.

2. The urine travels to the bladder where it’s stored. Finally, it’s expelled through the urethra.

SOLID WASTE LIQUID WASTE

Remember!

Our bodies also remove

waste by exhaling and

sweating.

Why is healthy food important?

Vitamins are essential for our bodies, but we don’t produce them. Without these vitamins, we can feel tired or get ill easily. If we eat a healthy diet, our bodies will get all the vitamins we need and we’ll feel healthy.

Food that contains high levels of sugar or fats is called junk food. Our bodies don’t need much sugar or fat. If we eat too much of them, they can accumulate in our bodies. This causes us to gain weight and sometimes causes illness too.

We should eat the right kinds of foods in the right proportions. For example:**more grains and vegetables than other types of food**

**not too many dairy products such**