3 Face develops from 5 projections: frontonasal process (ectoderm over forebrain) + 2 maxillary processes + 2 mandibular processes (1st arch)An ectodermal olfactory placode divides fronto-nasal process into medial nasal & lateral nasal process, which give rise to external nasal skeletonOlfactory placode deepens into olfactory pit & later olfactory sac which forms nasal cavitiesNasal septum develops from mesodermal tecto-septal expansion from Rathke’s pouch
27 Lateral Nasal Wall 3 - 4 bony conchae covered with mucosa to form turbinates. Space below & lateralto turbinate is called meatus. Middle meatus contains a round bullaethmoidalis separated from uncinateprocess by hiatus semilunaris that leadsto a funnel shaped ethmoidal infundibulum.
28 Meatal Drainage1. Inferior meatus: Nasolacrimal duct ( guarded at its end by a mucosal valve called HASNER’s valve )2. Middle meatus:a. Frontalb. Anterior ethmoidc. Maxillary (natural + accessory ostia)3. Superior meatus: Posterior ethmoid4. Spheno-ethmoidal recess: Sphenoid
67 Muco-ciliary blanketGoblet cells in nasal mucosa secrete a mucous blanket; moved backwards like a conveyer belt into nasopharynx.Consists of: Superficial mucous or gel layer Deep serous or sol layer