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 seperatesit 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

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• 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 buccopharyngealmembrane.

• 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.

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• 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+ frontonasalprocess

• 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

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• 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 procedesbackwards.

• 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 frontonasalprocess 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 anamoulouscommunication between mouth and nose –unilateral or bilateral.

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39Prof. Makarem

40Prof. Makarem

41Prof. Makarem

Prof. Makarem 42

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