Development of face

DEVELOPMENT OF FACE, NOSE AND PALATE

Development of Face
Face is developed from 5 processes (prominences): One fronto-nasal process, 2 maxillary processes and 2 mandibular processes. Maxillary process is a foreward growth of dorsal end if 1st pharyngeal arch. Mandibular process is a forward growth of ventral end of 1st pharyngeal arch. These processes surround stmodeum (primitive nasal and oral cavities). Bucco-pharyngeal membrane will rupture to allow continuity between oral and pharyngeal cavities.

Fronto-nasal Process

Nasal placode: rounded thickening in the lower lateral parts of the fronto-nasal process. Nasal pits & swellings: invagination of placode will form nasal pits which are surrounded by medial & lateral nasal prominences (folds). Intermaxillary segment: from fused medial nasal prominences . It forms intermaxillary segments that form middle part of nose, filtrum, part of upper jaw that carries upper 4 incisors and primary palate.

Maxillary Process

It is separated from side of fronto-nasal process by naso-lacrimal groove, inside which a cord of ectodermal cells is formed then becomes canalized to form naso-lacrimal duct. Its upper end forms lacrimal sac. Maxillary process fuses with fronto-nasal process covering naso-lacrimal duct. It forms lower boundary of nasal pit. It is separated from other maxillary process by intermaxillary segment.


-It also fuses partially with mandibular process to form the cheek. -Palatine process is formed as inward projection of maxillary process to form secondary palate which divides stomodeum into upper nasal and lower oral cavity. So maxillary process forms upper part of cheek, upper lip except filtrum, upper jaw except part that carries upper incisors and most of hard palate.

Mandibular Process

It forms lower part of cheek, whole lower lip and lower jaw and floor of mouth. Development of palate: 1- Primary palate: from intermaxillary segment of fronto-nasal process. 2- Secondary palate: from palatine processes of maxillary processes that form most of hard palate and soft palate. -Hard palate receives downward growth of nasal septum.

Congenital Anomalies of Face & Palate

1- Inclusion dermoid: cystic swelling at line of fusions between processes of the face. 2- Oblique facial cleft: failure of fusion between maxillary and fronto-nasal processes. 2- Macrostomia or Microstomia : defective or marked fusion between maxillary and mandibular processes. 3- Cleft (hare) lip: cleft lip due to failure of fusion between maxillary process and intermaxillary segment. 4- Cleft palate: failure of fusion between different parts that form palate. It could be: A- Unilateral complete cleft palate. B- Bilateral complete cleft palate. C- Partial cleft palate. D- Cleft uvula.

Development of Mouth & Salivary glands

Mouth: It is developed from lower part of stomodeum (below developed hard palate) and anterior part of foregut. Line of demarcation lies behind the gum. Salivary glands: Parotid: from ectodermal outgrowth of buccal mucosa. Its dorsal part gives several buds to form acini of the gland. Its ventral part is canalized to form the duct. Submandibular & sublingual: developed from endodermal buds from floor of mouth.