Unit 20. The digestive system. Foods.

WARM-UP: Name all parts of the digestive system and explain their functions.

VOCABULARY: Learn the following words and word combinations.

Insoluble digestion to digest esophagus stomach cardiac region small intestine large intestine fundus pyloric region to break up gastric juice solid rectum to expel carbohydrates fats proteins liver sodium chloride potassium iron magnesium

Guess the meaning of the following words.

Chemical nutrients; molecule; lymphatic system; bloodstream; to absorb; to swallow; muscular tube; rib; enzyme; inorganic and organic food; substance; nutrition; muscles; source of energy; growth; minerals; vitamins; bones; teeth; skin.

Practice the following for pronunciation.

molecule [ˈmɒl.ɪ.kjuːl]

insoluble [ɪnˈsɒl.jʊ.bl ̩]

digestion [da ɪˈdʒes.tʃən]

digest [da ɪˈdʒest]

esophagus [ɪˈsɒf.ə.gəs]

stomach [ˈstʌm.ək]

intestine [ɪnˈtes.tɪn]

pyloric region [paı’lɒrık ˈriː.dʒn]

fundus [‘fʌndəs]

gastric juice [ˈgæs.trɪk dʒuːs]

enzyme [ˈen.zaɪm]

hydrochloric acid [ˌhaɪd.rə.klɒr.ɪkˈæs.ɪd]

rectum [ˈrek.təm]

expel [ɪkˈspel]

carbohydrate [ˌkɑː.bəʊ ˈhaɪ.dreɪt]

protein [ˈprəʊ.tiːn]

sodium [ˈsəʊ.di.əm]

potassium [pəˈtæs.i.əm]

iron [aɪən]

magnesium [mægˈniː.zi.əm]

READING: Read the text and do the tasks that follow.

Every cell of the human body requires certain chemical nutrients. To supply them the body must break down complex foods into molecules to pass through tissues and be delivered by blood or lymphatic systems to the various body cells. This break of insoluble forms is known as digestion.

Digestion begins when we put food in our mouth and ends when the food has been absorbed into the bloodstream. When we chew, our teeth break up the food into small pieces for swallowing. Food then travels down a muscular tube called the esophagus, to the stomach. The stomach is a thick muscular sac positioned on the left side of the body just beneath the ribs. The upper region of the stomach, closest to the heart, is called the cardiac region. Below that is the cresent part of the sac called the fundus. The pyloric region is tubular and connects the stomach to the small intestine. The wall of the stomach is made up of three thick layers of muscle. The powerful contraction of these muscles break up the food, mix it with gastric juice, and move it down the tract. Gastric juice is a mixture of hydrochloric acid and enzymes that further digest the food. In the small intestine food is broken up into useful substances and waste substances by enzymes. Inside the small intestine villi absorb the useful substances into the bloodstream. Waste substances remain and pass into the large intestine, where water is absorbed until the waste becomes solid. This waste is later expelled from the rectum.

Foods are substances which when taken into the body yield energy on oxidation, build new tissue, repair old tissue and play an essential role in growth and nutrition. Foods are to be divided into two general classes. These are inorganic and organic foods. The former class includes inorganic salts and water. The latter class includes carbohydrates, fats and proteins.

Proteins are found most abundantly in muscles. Fat is concentrated in the fat cells under the skin and around the intestines. Carbohydrates are found mainly in the liver, muscles and blood. Carbohydrates are known as the chief source of energy. The absence of carbohydrates upsets the fat and protein metabolism. As for the minerals, high levels of calcium and phosphorus form part of the bones and teeth, sodium and chloride are found mainly in the body fluids, potassium is the main mineral in the muscles, iron is essential to red blood cells, and magnesium is found throughout the body.

Other types of food (vitamins) needed in very small amounts for various functions of the body are essential. They are found in certain foods and are necessary for the growth, development and general health of the body. Such foods include milk and many products made from it, all green leafy vegetables like cabbage, spinach, other fresh vegetables, fruits and fruit juices, whole-grained cereals, eggs and number of others. You determine how you feel throughout each day by the type of breakfast you eat. Your energy production, which corresponds to the quality of sugar available, determines how you think, act and feel.