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1. Find the examples of Gerund in the text, state the functions of the verbs.

2. Insert the prepositions where it is necessary:

1. The digestive system consists … the alimentary canal and related or accessory organs. 2. The alimentary canal is formed … the mouth, pharynx, esophagus, stomach, small intestine, large intestine and rectum. 3. The oral and laryngeal portions of the pharynx serve … a channel … the passage … both food and air. 4. The reduction of food is accomplished … the masticatory apparatus. 5. A large receptor area is responsible … the perception of external stimuli. 6. The vitamin deficiency results … hemorrhage, and edema of the gingival connective tissue. 7. This growth is correlated … and dependent … the erup­tion of teeth. 8. Considerable hemorrhage followed … the tooth extraction.

3. Translate the sentences, define non-finite verb forms.

1. This syndrome is quite serious; if unrecognized and untrea­ted, it may result in death. 2. The contact point is the point on the proximal surface of a tooth which touches a neighbouring tooth. 3. Pre-pain sensation, elicited by three kinds of electrical sti­mulation in human maxillary anterior teeth of adult men, was investigated. 4. In March the patient returned to the office complai­ning of a vague pain in the maxillary left posterior region. 5. The patient, a 24-year old male, appeared in January complaining of pain in the maxillary left posterior region and the sensation of something growing there. 6. In a report the author stated that caries was inhibi­ted by the same water, containing flouride that produced mottled enamel. 7. Denture laboratories are described, three of them being one-man laboratories. 8. The number of teeth extracted for various reasons was from 1 to 6, the average being 4 in both groups of patients. 9. Several large scale investigations have been conducted, with encouraging results reported. 10. The tooth was embedded in the lingual soft tissues, with root pointing backward. 11. Treatment consists of removing and correcting local irri­tating factor and providing the child with a nutritionally balan­ced diet and dental prophylaxis.

Summary

The chemical reduction of food

After a mouthful has been taken, both up-and-down, side-to-side movements enable the teeth to crush and break the food into fragments of proper size for swallowing. Particle size may vary up to 12 mm in diameter but generally it is less than 2 mm. After mastication the mass weighs from 3 to 6 grams. The food becomes moistened and softened by the saliva. The chemical action taking place in the mouth is accomplished by means of the first digestive secretion, the saliva.

The saliva assists in mastication in several ways: by dissolving some of the readily soluble food components; by partly digesting some of starch; by softening the mass of food; by covering the bolus with mucus so as to make it more easily moved about in the mouth.

Saliva is slightly alkaline in reaction with a pH between 6.35 and 6.85. The amount secreted in twenty-four hours is about 1300 cc. It consists of 99.5 per cent water and 0.5 per cent total solids. Its chief constituents are water, inorganic salts, mucin, serum albumin and serum globulin, and salivary amylase. The chemical change is effected by salivary amylase which acts on the boiled starch changing it to dextrin and possibly to maltose.

Salivary digestion is important in preparing the food for the changes that follow. Saliva dissolves some of the solid substances so that they are brought in contact with the taste buds; thus they stimulate appetite and result in series of reflexes which increase the flow of gastric juice and augment salivary secretion as well.

Speaking

Speak on the role of the oral cavity structures in the digestion.

Unit VII. Oral cavity abnormalities

Lead-in

This unit considers anatomical and functional abnormalities of the oral cavity structures. You will learn about the tooth anomalies (both in number and structure), malocclusion and cleft formations. All of them influence the human organism in a number of ways and often (if untreated) may result in severe diseases.

Reading