IV. Устная речь. Направлено на формирование компетенции ок-6.

Choose any of the oral structures anomalies to dwell on. Speak on the frequency of its occurrence, predisposing factors, possible complications and prognosis.

Занятие 9

Этапы занятия:

I. Изучающее чтение. Направлено на формирование компетенции ок-5 Facial clefts

Aberrations in embryonic facial development lead to a wide variety of defects. Although any step may be impaired, defects of primary and secondary palate development are most common.

Most cases of clefts of the lip with or without associated cleft palate appear to form a group etiologically different from clefts involving only the secondary palate. For example, when more than one child in family has facial clefts, the clefts are almost always found to belong only to one group.

There is some evidence that underdevelopment (small size) of the medial or lateral nasal prominences is involved in primary palate clefting, so the contact at the site of fusion is either prevented or inadequate. Other data present the evidence that many cases of cleft lip result from a combination that together reduce the mesenchyme in the primary palate at the point of fusion by an amount sufficient to prevent normal contact and fusion. About two thirds of patients with clefts of the primary palate also have clefts of the secondary palate. Studies of experimental animals suggest that excessive separation of jaw segments as a result of the primary palate cleft prevents the palatal shelves from contacting after elevation. The degree of clefting is highly variable. Clefts may be either bilateral or unilateral and complete or incomplete. Most of this variation results from differing degrees of fusion.

Clefts involving only the second palate constitute the second most frequent facial malformation in humans (after clefts involving the primary palate). Cleft palate can also be produced in experimental animals with a wide variety of chemical agents or other manipulations affecting the embryo. Usually, such agents retard or prevent shelf elevation. In other cases, although elevation occurs, the shelves are too small to make contact. There are also some proofs that the state develops after the application of some environmental agents.

Less frequently, other types of facial clefting are observed. In most instances they can be explained by failure of fusion between facial prominences of reduced size, and similar clefts can be produced experimentally. Examples include failure of merging and fusion between the maxillary prominence and the lateral nasal prominence, leading to oblique facial clefts, or failure of merging of the maxillary prominence and mandibular arch, leading to lateral facial clefts (macrostomia). Other rare facial malformations (including oblique facial clefts) may also result from abnormal pressures or fusions with folds in the fetal (e.g., amniotic) membranes.