Physiology of the alimentary tract

The first step in the alimentary system can begin before the food is in your mouth. When you smell or see food, you start to salivate, thus beginning the digestive process.

Food is the body's source of fuel. Nutrients in food give the body's cells the energy they need to operate. Before food can be used, it has to be broken down into tiny pieces. Then it is easy to absorb by the body. In humans, proteins are broken down into amino acids, starches into sugars, and fats into fatty acids and glycerol.

During digestion two main processes occur at the same time:

· Mechanical Digestion: larger pieces of food break down into smaller pieces before the chemical digestion. Mechanical digestion starts in the mouth and continues in to the stomach.

· Chemical Digestion: several different enzymes break down macromolecules into smaller molecules. They are absorbed more efficiently. Chemical digestion starts with saliva and continues into the intestines.

In the alimentary tract the food really passes through the body rather than being in the body. The smooth muscles of the tubular digestive organs move the food efficiently along as it is broken down into absorb-able atoms and molecules. During absorption, the nutrients that come from food (such as proteins, fats, carbohydrates, vitamins, and minerals) pass through the wall of the small intestine and into the bloodstream and lymph. In this way nutrients are distributed throughout the rest of the body. In the large intestine there is re-absorption of water and absorption of some minerals and feces are formed.

Digestion begins in the mouth. A brain reflex triggers the flow of saliva when we see or think about food. Saliva moistens the food while the teeth chew it up and make it easier to swallow. The digestive enzyme in saliva, starts to break down starch into simpler sugars before the food leaves the mouth. The nervous pathway involved in salivary excretion requires stimulation of receptors in the mouth, sensory impulses to the brain stem, and parasympathetic impulses to salivary glands.

Swallowing your food happens when the muscles in your tongue and mouth move the food into your pharynx. The pharynx is the passageway for food and air. A small flap of skin called the epiglottis over the pharynx prevents food from entering the trachea and thus choking.

Exercise 8. Answer the following questions to the text:

1. When does the digestive process begin?

2. How many processes occur during digestion?

3. What is the difference between mechanical and chemical digestions?

4. What is the function of the smooth muscles?

5. What nutrients come from food during absorption?

6. What is the role of saliva in mastication?

7. What is the function of the enzyme?

8. How does the process of swallowing occur?

Exercise 9. Translate the following word combinations into English:

Початок травного процесу, виділяти слину, давати енергію клітинам тіла, білки та вуглеводи, розщеплювати жири на жирні кислоти і гліцерин, жування та ковтання, хімічне травлення, поглинати більш ефективно, розподілити по всьому тілу, рефлекторно викликати потік слини, вимагати стимуляції рецепторів, поширюватися по тілу, запобігти потрапляння в трахею, зволожити їжу, прохід для їжі та повітря, джерело топлива, поглинання мінералів.

Exercise 10. Match the terms with their definitions:

Exercise 11. Arrange the following sentences in a correct order to describe the following term “enzyme”:

1. Enzyme does not control the direction of the reaction, it increases the rates of the reactions.

2. A substance produced by the body to assist in a chemical reaction.

3. Very few biochemical reactions carry on at a significant rate without the presence of an enzyme.

4. It acts as a catalyst, increasing the rate at which a chemical reaction occurs.

5. The human body probably contains about 10,000 different enzymes.

Exercise 12. Guess what enzymes are produced by fallowing organs:

Exercise 13. Define forms of the gerund and functions in the sentence. Translate:

1. Overeating is bad for your health.

2. Asking him about his diagnose was useless.

3. The role of teeth in digestion is chewing the food.

4. The speed of moving the food through the esophagus depends on its size.

5. Eating with an open mouth is a bad habit.

6. There are many ways of solving this problem.

7. They went on eating.

8. Doctors are always ready for helping people.

Exercise 14. Put questions to the underlined words:

1. The alimentary tract is a twisting tube about 8½ metres long.

2. All food consists of proteins, fats and carbohydrates.

3. The mucosa is the inner layer of the alimentary tract.

4. The alimentary tract constantly releases hormones to help regulate the digestive process.

5. Saliva contains an enzyme called salivary amylase which begins the digestion of starch.

6. Some foods and drinks can affect the function of the esophageal sphincter.

7. Smoking also weakens the esophageal sphincter and can produce heartburn.

8. Scientists believe that between 500 and 1000 different species of bacteria live in the large intestine.

Exercise 15. Arrange the following sentences in a correct order to describe the following term “The alimentary tract”:

1. During digestion proteins, fats, carbohydrates, vitamins and minerals are broken down for better absorption.

2. It consists of the mouth, pharynx, esophagus, stomach, small intestine, and large intestine.

3. The alimentary tract is a musculomembraneous canal about 8½ metres in length.

4. The liver with gallbladder and pancreas are the large glands of the alimentary tract.

5. Three main processes take part in the alimentary tract: digestion, absorption and excretion.

6. It extends from the oral cavity to the anus.

Exercise 16. Continue the following sentences to describe the following term “digestion”:

1. Digestion is a process …...

2. Digestion begins …...

3. During digestion two main processes occur at the same time …...

4. Food is broking down into tiny pieces during …...

5. On chemical digestion enzyme in saliva starts …...

Exercise 17. Translate into English:

1. Жування — це процес механічної переробки їжі, що відбувається у роті.

2. Жування супроводжується виділенням слини.

3. Слина зволожує їжу, в той час як зуби пережовують її, для подальшого ковтання.

4. Ковтання відбувається, коли м'язи у язику та роті переміщують їжу у горло.

5. Надгортанник запобігає потраплянню їжі у трахею.

Завдання для самостійної роботи студентів (СРС)

Exercise 1. Topic Vocabulary:

Exercise 2. Read and translate:

bilirubin – an orange-yellow pigment, cirrhosis – type of liver disease, detoxification – neutralization of poisoning or smth., dialysis – the process of removing waste products and excess fluid, hepatocyte – hepatic cell.

Exercise 3. Form adjectives using the suffix:

- ive: effect, prevent, infect, protect, penetrate, digest, irritate, product, connect, associate, excess, infiltrate.

- ful: harm, use, pain, care, hope, success, beauty.

- al: function, accident, behavior, clinic, intestine, bacteria, nutrition, norm, artery, abdomen.

Exercise 4. Read and translate the word combinations into your native language:

Vital organ of vertebrates, lobes of unequal size and shape, the hepatic artery and the portal vein, blood containing digested nutrients, detoxification and protein synthesis, to release the hormone, to emulsify fats, to rid of harmful substances, survival, an incredible capacity for regeneration, to be prone to disease, to cause long-term damage to the liver, permanent scarring, liver failure.

Exercise 5. Read and translate the text: