Embryology 6 Lecture Notes PDF

EMBRYOLOGY6 Prof.Dr.Ban A.Ghani  In mammals, development of the face begins with the formation of five facial prominences surrounding the primitive mouth: the frontonasal prominence on the rostral side, a pair of maxillary prominences laterally and a pair of mandibular prominences caudally....

EMBRYOLOGY6 Prof.Dr.Ban A.Ghani  In mammals, development of the face begins with the formation of five facial prominences surrounding the primitive mouth: the frontonasal prominence on the rostral side, a pair of maxillary prominences laterally and a pair of mandibular prominences caudally.  These facial prominences are populated by cranial neural crest cells that originate at the dorsal edge of the developing rostral neural tube.  As development proceeds, the frontonasal prominence is divided into the medial and lateral nasal processes by the formation of nasal pits  Subsequent morphogenetic fusion of the lateral and medial nasal processes forms the nostril, and fusion between the medial nasal processes and the maxillary prominences forms the upper lip DEVELOPMENT OF PALATE AND ANOMALIES DEVELOPMENT OF PALATE AND ANOMALIES THE SECONDARY PALATE THE PRIMARY PALATE THE PALATINE UVULA CLEFT LIP AND CLEFT PALATE WHAT IS A CRANIOFACIAL ANOMALY? Palatal formation Tissue intervening between nasal and oral cavities is known as the palate. the primary palate, formed by the two maxillary and two medial nasal processes, separates the developing oral and nasal cavities. Subsequently, between 6th and 8th weeks, the secondary palate is formed from two palatal processes (outgrowths of the maxillary processes).Primary and secondary palates together form the definitive palate.  Begins at the end of the 5th week  Gets completed by the end of the 12th week  The most critical period for the development of palate is from the end of 6th week to the beginning of 9th week The palate develops from two primordia: The Primary palate The Secondary palate  The Primary Palate  Begins to develop:  Early in the 6th week  From the deep part of the intermaxillary segment, as median palatine process  Lies behind the premaxillary part of the maxilla  Fuses with the developing secondary palate The primary palate represents only a small part lying anterior to the incisive fossa, of the adult hard palate Primary palate Hard palate Secondary palate Soft palate  The Secondary Palate  Is the primordia of hard and soft palate posterior to the incisive fossa  Begins to develop:  Early in the 6th week  From the internal aspect of the maxillary processes, as lateral palatine process  In the beginning, the lateral palatine processes project inferomedially on each side of the tongue  With the development of the jaws, the tongue moves inferiorly.  During 7th & 8th weeks, the lateral palatine processes elongate and ascend to a horizontal position above the tongue Tongue  Graduallythe lateral palatine processes:  Grow medially and fuse in the median plane  Also fuse with the: Posterior part of the primary palate & The nasal septum  Fusion with the nasal septum begins anteriorly during 9th week, extends posteriorly and is completed by 12th week Bone develops in the anterior part to form the hard palate. The posterior part develops as muscular soft palate  Changes in Face during Fetal period  Mainly result from changes in the proportion & relative positioning of facial structures  In early fetal period the nose is flat and mandible underdeveloped. They attain their characteristic form during fetal period  The enlargement of brain results in the formation of a prominent forehead  Eyes initially appear on each side of frontonasal prominence move medially  Ears first appear on lower portion of lower jaw, grow in upper direction to the level of the eyes  What is a craniofacial anomaly? Craniofacial anomalies are deformities that affect a child's head and facial bones. These disorders are typically present at birth (congenital) and can range from mild to severe. Common craniofacial anomalies include: cleft lip and palate: a separation in the lip and the palate.  Facial clefts Failure of the embryonic facial prominences to fuse properly  May be unilateral or bilateral  May involve: Lead to  Lips only: Cleft lip difficulty in  Palate only: Cleft palate breathing  Lip & palate: Cleft lip & palate feeding  Region of nasolacrimal groove: Facial clefts sucking swallowing & speech  Median cleft lip: results from failure of the medial nasal prominences to merge and form the intermaxillary segments  Unilateral cleft lip: result from failure of the maxillary Median Cleft lip prominence to merge with the medial nasal prominence on the affected side  Bilateral cleft lip: results due to Unilateral cleft lip failure of maxillary prominences to meet and unite with the medial nasal prominences on both sides Bilateral cleft lip 2. Oblique facial cleft: results from failure of the maxillary prominence to fuse with the lateral nasal prominence 3. Cleft palate leaves the nasal and oral cavities connected & Oblique facial cleft results in nursing problem for the new born May be:  Anterior/posterior to incisive foramen  Unilateral/bilateral  Isolated/associated with cleft lips Cleft lip, cleft jaw & cleft palate CLEFT LIP coupled with clefts of the anterior palate or entire palate. COMMON CRANIOFACIAL ANOMALIES INCLUDE: cleft lip and palate: a separation in the lip and the palate craniosynostosis: premature closure of the soft spots in an infant’s skull hemifacial microsomia: a condition in which the tissues on one side of the face are underdeveloped vascular malformation: an abnormal growth composed of blood vessels hemangioma: a benign tumor that causes a red birthmark LEARNING OUTCOME SINCE FORMATION OF VARIOUS PARTS OF THE FACE INVOLVES FUSION OF DIVERSE COMPONENTS…. OCCASIONALLY THIS FUSION CAN BE INCOMPLETE GIVE RISE TO VARIOUS ANOMALIES……