Development of face and palate • After formation of head fold , developing brain & pericardium it forms two prominent bulgings on ventral aspect embryo. • these bulgings are seperated by stomatodeum • the floor of stomatodeum is formed by buccopharyngeal membrane, which seperates it from foregut.
• mesoderm covering developing forebrain proliferates & forms a downward projection that overlaps the upper part of stomatodeum.---this projection called frontonasal process. • pharyngeal arches are laid down in lateral & ventral walls of most cranial part of foregut •
• face thus develops from— • the frontonasal process • first pharyngeal arch of each side( mandibular arch)
• Human face development -begins - 4th week of embryonic development. • By 6th week external face is completed • Incidence of congenital malformations of the face is approximately 1 in 700 births
• Brain & heart bulging are separated by stomatodaeum. • floor of stomatodaeum is formed by buccopharyngeal membrane.
• mesoderm over developing forebrain proliferates, & projects downward (frontonasal process) that overlaps the upper part of stomatodaeum. • the mandibular arch gives off a bud from dorsal end – maxillary process, • it grows ventromedially cranial to main part of arch --- mandibular process. • the ectoderm overlying frontonasal process soon shows bilateral localised thickenings , a little above stomatodeum ---nasal placodes. • the placodes soon sink below the surface as nasal pits . • the raised medial edge is called—medial nasal process, • the raised lateral edge is called—lateral nasal process. Face
• the mandibular processes of two sides grow towards each other , & fuse in midline, • thus it give rise to lower lip, lower jaw. • each maxillary process now grows medially and fuses first with the lateral then with medial nasal process & then with each other . Thus nasal pits are cut off from stomatodeum . • At the same time frontonasal process becomes much narrower from side to side , as a result the two external nares come closer. • • Maxillary prominences continue to increase in size & grows medially compressing nasal prominence Cleft b/w medial nasal prominence & maxillary prominence is lost, and the two fuse Upper lip is formed by two medial nasal prominences & two maxillary prominences. Lateral nasal prominences do not participate in formation of the upper lip. • Lower lip and jaw form from mandibular prominences that merge across the midline. • muscles of face are derived from mesoderm of second branchial arch , therefore supplied by facial nerve.
• Maxillary and lateral nasal prominences are separated by a deep furrow, nasolacrimal groove
• After canalization, cord forms the nasolacrimal duct; its upper end widens to form lacrimal sac.
• Maxillary prominences enlarge to form cheeks and maxillae. • nasal septum- • Philtrum -Globular part of median nasal swelling • Upper lip- maxillary process+ frontonasal process • Lower lip- mandibular process
nose
• recieves contributions from frontonasal process , medial & lateral nasal process of right & left sides . • external nares are formed when nasal pits are cut off from stomatodeum by fusion of maxillary process with medial nasal process. • frontonasal process becomes progressively narrower & its deeper part forms nasal septum. • mesoderm gets heaped up in centre to forms dorsum of nose, • groove appears b/w region of nose & bulging forebrain . • as nose becomes prominent the external nares come to open downwards instead of forwards. Nasal cavity
• formed by extension of nasal pits . • these pits are in open communication with stomatodeum • soon medial & laateral processes fuse & forms partition b/w pit & stomatodeum , this is called primitive palate.( derived from frontonasal process) • nasal pits now deepen to form nasal sacs which expand both dorsally & caudally . • the dorsal part of this sac is ,at first seperated from stomatodeumby a thin buccopharangeal membrane . • this membrane soon breaks down and thus nasal sac has a ventral orifice tht opens on the face (anterior nares / external nares) and a dorsal orifice that opens into stomatodeum ( primitive posterior aperture) • nasal cavities are seperated from mouth by developing palate. • lateral wall of nose is derived on each side ,from lateral nasal process.,conchae appear as elevations on lateral wall of each nasal cavity. Anomalies
• there may be atresia of the cavity at the external nares , or at posterior nasal aperture , can be unilateral or bilateral • rarely can be total absence of nasal passages. • congenital defects in cribriform plate of ethmoid can lead to communication b/w cranial cavity & nose. • nasal septum may not be in midline ---deviated to one side, • nasal septum may be absent • nasal cavity may communicate with mouth. Development of palate Development of Palate
The palate develops from two stages:
• Primary palate - 5th to 12th week • Secondary palate
30 • From each maxillary process a plate like shelf grows medially --palatal process • thus --- • two palatal process • primitive palate from frontonasal process. • definative palate is formed by fusion of these three parts --- • each palatal process fuses with posterior margin of primitive palate. • two palatal processes fuse with each other in midline .this fusion begins anteriorly and procedes backwards. • Posterior 1/3rd of hard is also contributed by horizontal plate of palatine bone . • medial edge of palatal processes fuse with free lower edge of nasal septum .thus seperating two nasal cavities from each other and from mouth. • at later stage mesoderm in palate undergoes intramembranous ossification to form hard palate .however ossification does not extend into most posterior portion ,which remains as soft palate . • the part of palate derived from frontonasal process forms the premaxilla ---that carries incissor teeth.
applied
• cleft palate • defective fusion of various components of palate give rise to cleft in the palate , • clefts of palate that extend to its anterior end are associated with harelip , as both the upper lip and the plate are formed by fusion of maxillary process with frontonasal process • clefts of palate result in anamoulous communication between mouth and nose – unilateral or bilateral.
38 Prof. Makarem 39 Prof. Makarem 40 Prof. Makarem 41 Prof. Makarem 42 Thank you