Essential Vocabulary

alimentary canal gallbladder

related (accessory) organs pancreas

esophagus to elicit

stomach twofold

small intestine temporomandibular joint (TMJ)

large intestine to grasp

rectum to swallow

liver to discharge

secretion stimulus (pl ?i)

enzyme taste buds

to ascertain odor

perception bolus

tactile to moisten

thermal

2. Translate the word combinations:

To contain accessory structures; to conduct food; to elicit salivary and gastric secretion; to undergo a twofold reduction; to grasp food; to discharge mucus, secretions and enzymes; to ascertain the features of food; to stimulate taste buds and olfactory epithelium; to release odors; to initiate gastric secretion; to moisten the food with saliva.

Read the text and determine the sequence of the digestive processes occurring in the oral cavity.

Digestion in the mouth. Mastication.

The digestive system consists of the alimentary canal and related or accessory organs. The alimentary canal is formed by the mouth, pharynx, esophagus, stomach, small intestine, large intestine and rectum. The accessory structures are the teeth, tongue, salivary glands, hard and soft palates, liver, gallbladder and pancreas. The oral and laryngeal portions of the pharynx serve as a channel for the passage of both food and air. Food is conducted through it from the mouth to the esophagus.

The sight, smell, and thought of food may elicit salivary and gastric secretion. These juices cannot be effective, however, before food enters the body. After the entrance into the mouth the food undergoes a twofold reduction: a mechanical one and a chemical one. The process of mechanical reduction of food is called mastication.

This reduction is accomplished by the masticatory apparatus formed by:

- a hard framework ? the skeleton and the temporomandibular joint;

- the muscles of mastication;

- a system of organs for grasping food and preparing it for swallowing (the lips, the

cheeks, muscles of facial expression, soft palate and tongue);

- special organs for mechanical grinding of the food ? the teeth;

- organs that discharge mucus, secretions and enzymes ? the glands;

- a specific nerve apparatus that ascertains the special qualitative features of the food

(the taste apparatus) and

- a large receptor area responsible for the perception of tactile, thermal and all other

types of external stimuli.

So mastication may be considered the first step in digestion. In man the act of mastication has more significance than the mere grinding of food before swallowing. While food is being chewed it is moved about in the mouth so that the taste buds are stimulated and odors are released to stimulate the olfactory epithelium. On these stimuli depends much of the satisfaction and pleasure of eating, which in turn initiate the process of gastric secretion.

The end product of mastication is the bolus, a mass of food moistened with saliva. In this form the food passes into the stomach.

Grammar

Date: 2016-06-12; view: 16