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FACE DEVELOPMENT Frontonasal prominence Mandibular prominence Maxillary prominence stomodeum Maxillary and lateral nasal prominences are separated by Nasolacrimal groove Nasal placode Frontonasal process • Latral nasal process • Nasal pit • Medial nasal process (globular process). Latral nasal process Nasal pit Medial nasal process • Medial N. P. • Lateral N.P. • Maxillary P. • Mandibular P. Medial N. P. Lateral N.P. Max. P. Mand. P. PALATE DEVELOPMENT The primary palate • Primary palate The secondary palate • palatal shelf tongue tongue The motive force for shelf elevation is not clearly elucidated: • Contractile fibroblast in the palatine processes may be involved. • The displacement of the tongue downward helps in the elevation of the two palatine processes. • The oral surface of the folds grows more rapidly than nasal surface that occurred by differential growth of the mesoderm, thus leading to rapid change in the position of the fold away from the faster growing side. tongue • Medial n.p. • Lateral n p • Maxillary p • Palatin p. • Medial n.p. • Lateral n p • Maxillary p • Primary palate • Palatin p. Fusion of palatine processes For fusion of palatal shelves to occur and for fusion of any other processes, it is necessary to eliminate their epithelial covering at the line of fusion • To achieve this fusion there is cessation of DNA synthesis and cell division within the epithelium 24-36 hours before epithelial contact. • This leads to sloughing of the surface epithelial cells and then they undergo physiologic cell death (apoptotic cell death) to expose basal epithelial cells. • These basal cells have an extra cellular surface substances particularly glycopoteins that enhance adhesion between the shelf edges as well as between the shelves and inferior margin of the nasal septum. • The epithelial cell debris is phagocytosed by ectomesenchymal cells. Not all the epithelial cells are lost in this process some cell rests remain in clusters (cell rests) along the fusion line. • Recent studies indicate that some epithelial cells undergo direct transformation to mesenchmal cells. TONGUE DEVELOPMENT Tongue is composed of: • Mucous membrane • Muscles( intrinsic and extrinsic) • Papillae( filiform, fungiform, circumvallate, foliate) • Salivary gland • Lingual tonsil Tongue Mucous Membrane 1st arch 2nd arch 3rd arch • Anterior two thirds • Posterior third • Epiglottis Summary Development of the tongue muscles • During the 2nd month IU the muscles of the tongue develop (intrinsic and extrinsic). • Some authors believe that the intrinsic muscles of the tongue are derived from the mesenchyme of the branchial arches sharing in the tongue development. • The intrinsic and extrinsic muscles of the tongue are developed from the occipital myotomes. These myotomes migrate and invade the tongue to from its musculature and carrying with them the hypoglossal nerve. Tongue papillae 1- Filliform pap. 2- Fungiform pap. Taste bud 4- Folliate pap. 3- Circumvallate pap. Development of circumvallate papilla Taste bud Taste pore 1- Outer supporting cell 2- Inner supporting cell 3- Neuroepithelial cell Taste sensation Bitter Sour Salt Sweet Innervation of the tongue: • A-Sensory innervations: • 1-Anterior two thirds (Lingual nerve and Chorda tempani) • 2-Posterior one third (Glossopharyngeal nerve) • B-Motor innervation: Hypoglossal nerve.