UNIT 3 NATURAL SCIENCE: NUTRITION

WHAT IS THE NUTRITION?

The nutrition is a combination of processes which supply our body with the building materials and energy we need to live.

NUTRIENTS

Food contains simple substances called nutrients, which provide the building materials and energy our body needs to grow and work. Nutrients are classified into groups:

• Carbohydrates: provide a fast supply of energy. We can find it in cereals, potatoes, bread, pasta...
• Fats: provide a slower supply of energy. They are mainly found in oils and butter.
• Proteins: provide building materials for growth and to repair our body. They are mainly found in meat, fish, eggs, milk...
• Vitamins and minerals: are necessary for our body to function properly. They are mainly found in fruit, vegetables and dairy products.
• Water: transport other nutrients and waste around the body.

HOW NUTRITION WORKS

There are 4 processes involved in nutrition:

• DIGESTION
• RESPIRATION
• CIRCULATION
• EXCRETION

DIGESTION: THE DIGESTIVE SYSTEM

Digestion is the process of breaking down food into nutrients that our body can use. It normally takes our body 24 to 48 hours to digest food. Digestion takes place in the digestive system.

The digestive system consists of one long tube, called the digestive tube, and the helper glands. These are the stages of digestion:

• It begins in the mouth, where our teeth break down food. While we chew, the food mixes with saliva produced by salivary glands. This mixture is called bolus. When we swallow, the bolus is pushed into the pharynx and down the oesophagus. 
• Then, the bolus reaches the stomach, which produces gastric juices. These juices break down food even further, forming a thick mixture calle chyme.
• The chyme travels to the small intestine, which produces intestinal juices. These juices combine with bile, produced in the liver, and pancreatic juice, produced in pancreas. The chyme turns into a milky liquid called chyle.
• Nutrients are absorbed into the blood in the small intestine. The inside of small intestine is covered with tiny finger-like projections, called vili, which help to absorb the nutrients.
• In the large intestine, water is absorbed and the remaining undigested food parts turn into solid faeces. Faeces leave the body through the anus.

HEALTHY HABITS IN RELATION TO DIGESTION

• Have a variet and healthy diet.
• Eat vitamins and minerals.
• Avoid fats and sugar.
• We need to eat 5 times in one day.
• We need to drink 2 liters of water per day.
• 5 pieces of fruit per day.

THE RESPIRATORY SYSTEM

Respiration is the process by which we breathe in, or inhale, to obtain the oxygen our body needs, and we breathe out, or exhale, to expel the carbon dioxide our body produces. Respiration takes place in the respiratory system.

The respiratory system consists of the air passageways and the lungs. 

When we inhale, air enters through the nostrils, goes to the pharynx, then travels down the larynx and the trachea. The trachea is divided into two branches called the bronchi. The bronchi take the air to each lung.

Inside the lungs, the bronchi are divided into smaller branches called bronchioles. The bronchioles lead to the air sacs. Air sacs are most surfaces in the lungs where gas exchange takes place.

GAS EXCHANGE

The air sacs in the lungs are surrounded by tiny blood vessels. Both the air sacs and the blood vessels have very thin walls. This allows oxygen and carbon dioxide to pass between the lungs and the blood.

• The oxygen in the air we inhale passes from the air sacs into the blood. The blood caries the oxygen to all the cells in our body.
• The carbon dioxide produced by all the body cells travels through the blood and passes into the air sacs. The air sacs expel the carbon dioxide when we exhale.

HEALTHY HABITS IN RELATION TO RESPIRATION

• Do exercise regularly.
• Breathe with your nose.
• Do not smoke.
• Avoid places with high levels of air pollution.