Chapter 56. Congenital Malformations of The Lip and Palate - Review of Medical Embryology Book

Cleft lip and palate are common malformations of the face and palate. Although often associated, cleft lip and palate are embryologically and etiologically separate malformations. They originate at different times in development and relate to different developmental processes

CLEFT PALATE AND CLEFT LIP have mixed environmental and genetic causes. The genetic causes are of greater importance in cleft lip with or without cleft palate than they are in cleft palate

Clefts of the lip and alveolar processes that continue through the palate are usually transmitted by a sex-linked male gen Bilateral cleft lip and palate are common in trisomy 13 syndrome and occur at the time of coalescence of the facial swellings (weeks 5 to 8) which results in an abnormal persistence of a fissure

CLEFT LIP is usually an upper lip malformation with or without cleft palate and is seen in 1/900 births and more frequently in males. Clefts vary from small notching of the lip's red border to extending into the floor of the nostril and through the alveolar bridge. It may be unilateral or bilateral

Unilateral cleft lip: failure of the maxillary prominence on the affected side to join with the merged medial nasal prominences, resulting in a persistent labial groove
Bilateral cleft lip: failure of the mesenchymal masses of the maxillary prominences to meet and merge with the merged medial nasal prominences. Defects may or may not be similar, with varying degree of defects on each side
Median cleft lip: very rare; caused by a mesodermal deficiency. Partial or complete failure of the medial nasal prominences to merge and form the intermaxillary segment

Characteristic feature of Mohr's syndrome (transmitted as an autosomal recessive trait)
Is really the only type of a true harelip

CLEFT PALATE: with or without cleft lip is seen in about 1/2500 births and may involve only the uvula or extend through the soft and hard palates. In severe cases, with cleft lip, it may extend through the alveolar process and lips of both sides

Its embryologic basis is failure of the mesenchymal masses of the lateral palatine processes to meet and fuse with each other, with the nasal septum, and/or with the posterior margin of the median palatine process or primary palate
It may be either unilateral or bilateral
Clefts of the anterior or primary palate occur anterior to the incisive foramen and are caused by a failure of the lateral palatine processes to meet and fuse with the primary palate
Clefts of the anterior and posterior palate involve both the primary and secondary palate and are caused by failure of the lateral palatine processes to meet and fuse with each other, the primary palate, and the nasal septum
Clefts of the posterior or secondary palate: these clefts are posterior to the incisive foramen and are caused by a failure of the lateral palatine processes to meet and fuse with each other and the nasal septum