Alveolar Processes and Alveolar Bone

 

The mucous membrane covering the alveolar processes is of two types. That part which is continuous with the sulcus, the alveolar mucosa, is thin and loosely attached to the underlying bone by thin connective tissue. This allows it to accommodate to the free movement of the lips and cheeks and permits the painless deposition of local anaesthetic into the underlying connective tissue. The thinness and the plentiful blood supply give it a red colour. In health, the alveolar mucosa is separated by a scalloped line, the muco-gingival junction, from a band of thicker tissue - the gingiva - which are keratinized and which surround the teeth in a band approximately 5 mm thick.

Like all bones, the alveolar bone consists of outer and inner cortical plates, between which lies the cancellous bone. Between the two cortical plates are the tooth sockets which are lined by a thin plate of bone, termed the lamina dura. This is visible on dental radiographs and is often of diagnostic importance. Into the alveolar lamina dura are inserted the ends of the periodontal fibres which, like those inserted into the cementum, are called Sharpey's fibres. The lamina dura is also pierced by a large numbers of bony canals called Volkmann's canals and, for this reason, it is often referred to as the cribriform plate.

The thickness of the labial and lingual alveolar cortical plates varies considerably from one area to another and from person to person and this has a significance when inflammatory periodontal disease affects the tissues. It tends to be thin on the labial aspect of the anterior teeth and may even be completely missing in places, which is termed a dehiscence. Dehiscences may be a leading factor in the occurrence of localized severe gingival recession.

The bone of the alveolar process is not static but is being continually remodelled by osteoblasts and osteoclasts. Both these cells are present in the tooth socket and it is by their action that teeth can move bodily through the bone, either during growth or during orthodontic treatment. The bone of the socket on the side towards which the tooth is moving is resorbed by osteoclasts, while more bone is deposited on the opposite side by osteoblasts.

 

Reading 2

1. Memorize pronunciation and learn the following words:

jaw челюсть cover покрывать

cheek щека change менять(ся)

gland железа remain оставаться

gland железа send направлять

salivary слюнный duct проток, канал

parotid околоушный cut разрезать

uvula (pl uvulae) язычок manufacture производить

tissue ткань health здоровье

 

Oral cavity

 

The mouth is the first division of the alimentary canal. Important structures of the mouth are gums with teeth and the tongue.

The tongue is composed of a number of highly mobile muscles covered with a special kind of mucous membrane that includes taste-buds. The very movable front part is called the tip; the more or less fixed one, the root. The tongue is very flexible. It is richly supplied with nerves and blood vessels. The tongue is essential to the production of speech, to the swallowing of food and to the sense of taste.

The soft and hard palate and salivary glands are in the oral cavity. The palate is the roof of the mouth. It consists of the hard palate in front, a bony structure covered with mucous membrane, and a soft palate, composed of nine small muscles, behind. The soft palate is a continuation of the soft tissues covering the hard palate. By changing the shape of the mouth, the soft palate is an important organ in the production of speech.

If you open the mouth, you will see the uvula. The uvula is a prolongation of the centre of the soft palate. It is the "little grape" of muscle tissue that hangs down from the roof of the mouth. It is part of the soft palate and an important organ for speech. On each side of the uvula there are tonsils.

The tonsils are a pair of almond-shaped lymphoid-tissue masses in the back of the throat. Sometimes they are large, sometimes are small. Like all lymph tissue, they release phagocytes that destroy bacteria. Sometimes, however, they themselves become overwhelmed with infection and are chronically diseased. This inflammation of the tonsils, called tonsillitis, is usually evidenced by a sore throat.

There are four glands, salivary glands, which secrete saliva. Sublingual gland lies under the tongue and submaxillary in the neck under the jaw. The two largest, called parotid glands and its little "auxiliary" lie between the cheek and a flat muscle band. The saliva is sent to the mouth through the duct.

The functions of the teeth are obvious: to chew food and mix it with saliva, to aid speech, and to maintain the position of the jaws. Primarily, the teeth are part of the digestive system. The food we choose to eat is cut by the teeth. The teeth get it ready for the stomach and intestines. If the teeth do their work well, the body is more likely to remain healthy, and if the body is healthy, the teeth are likely to remain strong.

Grammar

1. M ake questions on the anatomical structure of the mouth.

2. Find the sentences with the verb to be. State its functions.