DIGESTION
You should know… Nutrition is essential for life and proper growth –it affects our physical, mental and emotional development. We need to eat healthy food for our main meals –breakfast, lunch and dinner– and for snacks between meals, in the morning or the afternoon. Breakfast is a very important meal, especially for young people. They should have grain products, like bread, cereal or biscuits, and some dairy products, like milk, cheese or yoghurt. Fresh fruit and juice are also important because they have got lots of vitamins and minerals. Do you have these foods for breakfast?
Activities 1. Copy the true sentences into your notebook. a. Food affects the way that people grow. b. We should only eat three times every day: at breakfast, lunch and dinner. c. Fresh fruit contains vitamins and minerals. 2. Read the description of what Marta’s having for breakfast. Are they healthy foods? What foods are missing? Marta’s having toast with olive oil and some tomato. She’s also having fresh orange juice. 3. What do you usually have for breakfast? Are you missing any types of food?
THE DIGESTIVE SYSTEM When you eat food, your body has to break it down into basic nutrients. These are simple substances that your body can absorb. Your cells transform these nutrients and use them to perform basic life processes. The digestive system breaks down food into nutrients. Then it absorbs the nutrients and eliminates the waste. The digestive system includes the alimentary canal and various glands that produce digestive juices.
THE DIGESTIVE SYSTEM
The alimentary canal The alimentary canal has got many parts: The mouth is where digestion starts. The teeth, tongue and salivary glands are in the mouth.
The pharynx connects the mouth to the oesophagus.
The oesophagus is a long tube. It takes food from the pharynx to the stomach.
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The stomach is an organ that looks like a bag. It produces gastric juices to break down food.
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The small intestine is a long, thin tube. It goes from the stomach to the large intestine. It has got three parts: the duodenum, the jejunum and the ileum. The small intestine also produces intestinal juice.
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The large intestine is a short, thick tube. It includes the colon and the rectum, and ends at the anus.
Other glands Some are very important for digestion:
The salivary glands produce a liquid called saliva.
The liver produces a liquid called bile. First, the bile is stored in the gall bladder, and it goes into the duodenum during digestion.
The pancreas produces a liquid called pancreatic juice. During digestion, this juice also goes into the duodenum.
How does your digestive system work? Three different processes take place in your digestive system: digestion, absorption and elimination. ď‚—
Digestion
First, the food goes into your mouth. Your teeth cut and crush the food. Then your tongue mixes the food with saliva and forms a soft ball called bolus. The bolus goes to the pharynx and down the oesophagus to the stomach. Your stomach mixes the bolus with gastric juices. The bolus changes into a thick paste called chyme. Then the chyme goes into your small intestine.
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Absorption
In your small intestine, the chyme mixes with intestinal juice, bile and pancreatic juice. This makes a thin paste called chyle. Your small intestine absorbs the nutrients in the chyle. They go through the walls of the intestine and into your blood. Then the rest of the paste goes to your large intestine.
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Elimination
The paste that goes to the large intestine is mostly water and solid waste. The large intestine absorbs the extra water and changes the waste into feces. The feces finally leave the body though the anus.
Activities 1. Put the organs of the digestive system into the correct order of digestion, absorption and elimination. Mouth oesophagus small intestine anus stomach large intestine pharynx 2. Match the processes with the explanations. Absorption Your body breaks down the food. Elimination The nutrients go into your blood. Digestion The waste leaves the body. 3. Answer these questions: a. Where does the bolus form? b. Where does chyme form? c. Where does chyle form?
HEALTHY FOOD Most of our food comes from living things –plants and animals. We also consume some minerals, like salt.  Your food contains simple substances called nutrients. Some nutrients give your body energy to do things, and some nutrients help your body to work properly and stay healthy. The most important nutrients for your body are water, water carbohydrates, carbohydrates proteins, proteins fats, fats vitamins and minerals. minerals Water is essential. For example, when food breaks down in your digestive system, the nutrients dissolve in water. Then your body absorbs the nutrients and sends them to your cells. Â
Carbohydrates. Your body breaks down carbohydrates into sugar for energy. You can get carbohydrates from foods like bread, cereal, pasta and potatoes. Fats. Your body stores fats for extra energy. Fats help your body to grow and stay warm. You can get fats from oil, butter and cheese. Proteins. Your body uses proteins to grow and repair tissues, like muscles and skin. We get proteins from meat, fish, eggs, dairy products, beans and nuts. Vitamins and minerals. Your body needs vitamins and minerals to work properly and stay healthy. Fresh fruit and vegetables give you lots of vitamins and minerals.
Think about it! What does the diagram show? How many portions of fruit and vegetables should we eat every day? How many portions of dairy products should we have every day?
A balanced diet To grow and stay healthy, you need to eat foods that contain lots of nutrients. You should eat a varied and balanced diet with all of the nutrients that your body needs. This depends on your age, your sex and how much physical activity you do. A healthy diet includes a variety of foods from all of the food groups.
You should have a minimum of five portions of fruit and vegetables every day. You should drink a lot of water, too. Don’t eat a lot of fatty or sweet foods, like hamburgers or fizzy drinks.
Have a healthy breakfast with food like bread, cereal, milk, yoghurt, fruit and juice.
Eat slowly and chew your food well. Remember to brush your teeth after meals and snacks.
Did you realise? How big should a portion be? Use your hands and fingers to measure different foods. A closed hand = a portion of fruit. A cupped hand = a portion of cereal. An open hand = a portion of meat. Two fingers = a portion of cheese. The end of your thumb = a portion of butter.
Activities 1. What are the main nutrients in these foods? Carrots Milk Meat
Bread Banana Butter
2. Copy the true sentences into your notebook. You should have fruit and vegetables five or more times every day. You should always brush your teeth after meals or snacks. You should never eat any foods that contain fats.
Improvements in Nutrition Drinking water: It is the water we use to drink. Only a little portion of the fresh water around the planet is drinkable. Desalination is the process of cleaning the water to make it fresh and drinkable.
Preservation of food Because food is so important to survival, food preservation is one of the oldest technologies used by human beings. Food preservation is the process of treating and handling food in such a way as to stop or greatly slow down spoilage while maintaining nutritional value, texture and flavour. We’ll look at all of the different preservation techniques commonly used today.
Old methods Dehydration: It is the oldest method of food preservation. It removes moisture required for bacterial growth. There are many methods of dehydration, with the most common being the application of dry heated air. This causes evaporation of the surface water, which is replaced by water internally. Smoking is sometimes done in conjunction with drying. Although not sufficient by itself to permit long term storage of food, smoking adds chemicals that help inhibit microbial growth. Salting: It is the preparation of food with salt. Most bacteria, fungi and other potentially toxic organisms cannot survive in a highly salty environment.
Some modern methods Freezing: It is a common method of food preservation which slows both food dacay and the growth of microorganisms and, by turning water to ice, makes water unavailable for bacterial growth and chemical reactions. However, freezing only slows the deterioration of food; it does not stop it. And while it may stop the growth of microorganisms, freezing does not necessarily kill those microorganisms. Foods may be preserved for several months by freezing, but not indefinitely. Canning: It is a method of preserving food by first heating it to a temperature that destroys contaminating microorganisms, and then sealing it in air-tight jars or cans.