ЛЕКЦИЯ № 39. The progess of digestion

The process of digestion begins when food is taken into the mouth. Chewing Ы-еаго the food into smaller pieces, thereby exposing more surfaces to the saliva. Saliva itself has a double function. It moistens the food, so facilitating swallowing, and it contains the enzyme which begins the conversion of carbohydrates into simple sugars.

Although enzymatic action begins in the mouth, the major processes of digestion do not occur until the food passes down through the esophagus into the stomach. The stomach has both a chemical and a physical function. The walls of the stomach, which are protected by a layer of mucus, secrete gastric juices composed of several enzymes and hydrochloric acid. The most powerful enzyme is pepsin, which begins the process of converting proteins into amino acids. In addition, during these chemical reactions waves of contraction; and relaxation, known as peristalsis, move the walls of the stomach. They turn the food particles into a'semi-sqlid mass known as chyme.

From the stomach, the chyme passes into the small intestine through the pyloric sphincter. Much undigested food is still present Proteins have not been completely broken down, carbohydrates are still being converted into simple sugars, and fats remain in large globules. In the small intestine the process of digestion is completed by the action of the bile, which is secreted by the liver and released by the gallbladder, and by the action of various enzymes which are secreted by the pancreas and walls of the small in testine. Food which are still undigested pass on in a liquid state into large intestine. Absorption of the products of digestion taken place mainly through the wall of the small intestine.

Digestion

Chewing movements of the teeth, tongue, cheeks, lips and lower jaw break down food, mix it with saliva and roll it into a moist, soft mass called a bolus, suitable for swallowing.

Having been rendered suitable for swallowing the food is pushed back into the pharynx by the tongue, and enters the esopha gus to be transported rapidly down the neck and thorax, through the diaphragm to the stomach. The mucous membrane of the stomach is equipped with millions of glands secreting mucus, digestive enzymes and hydrochloric acid.

The small intestine is the region within which the process of digestion is completed and its products are absorbed. Although its epithelial lining forms many small glands, they mainly produce mucus. Most of the enzymes present are secreted by the pancreas, whose duct, opens into the duodenum. Bile from the liver also enters the duodenum.

The absorption of the product's of digestion also takes place in the small intestine, although water, salts, and glucose are ab sorbed from the stomach and the large intestine.

The large intestine is chiefly concerned with the preparation, storage and evacuation of undigestible and unabsorbable food residue.

New words

process of digestion – процесс переваривания

to begin – начинаться food – пища

to be taken – быть взятым

mouth – рот

diewing – жевание

smaller – меньший

pieces – части

thereby – таким образом

exposing – демонстрация

saliva – слюна

double – двойной

to moisten – увлажнять

facilitating – облегчение

contains – содержит

enzyme – фермент

conversion – преобразование

carbohydrates – углеводы

ашкя^ – хотя

action – действие

to pass down – передавать

through – через

stomach – живот

chemical – химикат

physical function – физическая функция

rendered – предоставленный

suitable – подходящий

tongue – язык

rapidly – быстро

equipped – оборудованный

hydrochloric acid – соляная кислота

absorption – поглощение

Спряжение глаголов в Past Simple Tense – правильные глаголы (действие совершалось в прошлом, когда время указано точно).

Спряжение глагола to work в Past Simple Tense Таблица 10

Спряжение глаголов в Past Simple Tense —неправильные глаголы Таблица 11

Перепишите следующий текст, употребив глаголы в прошедшем времени.

On Monday we have five lessons. The first lesson is Russian. At this lesson we write a dictation and do some exercises. Jack goes to the blackboard. He answers well and gets a «five». Pete does not get a «fi-ve'», because he does not know his lesson. After the second lesson I go to the canteen. I eat a sandwich and drink a cup of tea. I do not drink milk. After school I do not go home at once, I go to the library and take a book. Then I go home.

Answer the questions.

1. When the process of digestion begins?

2. What does chewing do?

3. Does saliva have a double function?

4. What does saliva contain?

5. Where does the enzymatic action begin?

6. What functions does the stomach have?

7. What is the most powerful enzyme?

8. What does pepsin begin?

9. By what is the food pushed back into the pharynx?

10. Where the absorption of the product's of digestion also takes place?

Make the sentences of your own using the new words (10 sentences).

Find the verb to be in the text. Explain why it is used in such a way?