EMBRYONIC DEVELOPMENT & STEM CELL COMPENDIUM
EMBRYONIC DEVELOPMENT & STEM CELL COMPENDIUM
57. Development of The Nasal Cavities
Review of MEDICAL EMBRYOLOGY Book by BEN PANSKY, Ph.D, M.D.
- The nasal pits deepen during week 6 due to the growth of the surrounding nasal swellings, also their penetration into the underlying mesenchyme. Thus, the primitive nasal cavities or nasal sacs (pits) each grow dorsocaudally in a position which is ventral to the developing brain
- EACH SAC (PIT), at first, is separated from the primitive oral cavity by the so-called oronasal membrane which soon breaks down and allows the nasal and oral cavities to communicate with each other via the primitive choanae, which lie posterior to the primary palate
- After the secondary palate develops, the choanae are at the junction of the nasal cavities and the pharynx
- Lateral palatine processes: when the lateral palatine processes fuse with each other and the nasal septum, the oral and nasal cavities are again separated. This results in a separation of the nasal cavities from each other
- The superior, middle, and inferior conchae or turbinates develop as elevations on the lateral nasal wall of each nasal cavity
- THE ECTODERMAL EPITHELIUM in the roof of the nasal cavities becomes specialized for olfaction
- The paranasal sinuses develop during late fetal life and in infancy as diverticula of the lateral nasal walls
- THE SINUSES extend into the maxilla, the ethmoid, and the frontal and the sphenoid bones during childhood and reach their mature size in the early twenties, whereupon they enlarge very slowly until death
- Developmental malformations of nasal cavities and nose
- ABSENCE OF NOSE: no nasal placodes form
- A SINGLE NOSTRIL: only one nasal placode forms
- BIFID NOSE: the medial nasal prominences do not merge completely. The nostrils are widely separated and the nasal bridge is bifid
