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6. Topics for discussion:

  1. Smoking or Health?

  2. Air pollution results in diseases of respiratory system.

III. Digestive and Excretory Systems

The energy required for maintenance and proper functioning of the human body is supplied by food. After it is broken into fragments by chewing and mixed with saliva, digestion begins. The food passes down the gullet into the stomach, where the process is continued by the gastric and intestinal juices. Thereafter, the mixture of food and secretions, called chyme, is pushed down the alimentary canal by peristalsis, rhythmic contractions of the smooth muscle of the gastrointestinal system. The contractions are initiated by the parasympathetic nervous system; such muscular activity can be inhibited by the sympathetic nervous system. Absorption of nutrients from chyme occurs mainly in the small intestine; unabsorbed food and secretions and waste substances from the liver pass to the large intestines and are expelled as feces. Water and water-soluble substances travel via the bloodstream from the intestines to the kidneys, which absorb all the constituents of the blood plasma except its proteins. The kidneys return most of the water and salts to the body, while excreting other salts and waste products, along with excess water, as urine.

Exercises

1. Work in pairs. Ask questions to the following statements and give full answers.

  1. The energy required for maintenance and proper functioning of the human body is supplied by food. (What…? What energy…? Why…? How much…?)

  2. Digestion involves both physical and chemical processes. (What processes…? What is understood by…?)

  3. Muscular activity can be inhibited by the sympathetic nervous system. (What…? How…? Why…?)

  4. The liver acts as a food processing factory for the absorbed foods. (Why…? What…?)

  5. Kidneys control the amount of water in our body. (Why…? What…? Where…?)

2. Make up sentences matching one part with the other.

  1. Digestion begins after…

  1. pass to the large intestines.

  1. Unabsorbed food and secretions…

  1. where the process is continued by the gastric and intestinal juices.

  1. Soluble food molecules are absorbed…

  1. plasma except its proteins.

  1. The food passes down the gullet into the stomach…

  1. into the blood capillaries of the small intestine.

  1. The kidneys return most of the water and salts to the body…

  1. while excreting other salts and waste products.

  1. The kidneys absorb all the constituents of the blood…

  1. food is broken into fragments by chewing.

3. Develop the idea expressing your point of view about the following:

  1. Problems in the digestive system occur when we develop bad eating habits.

  2. If both kidneys are affected, serious treatment is essential.