A nasal septum separates the nasal cavities. Most of the septum and the nasal cavities are lined by respiratory epithelium and its underlying lamina propria. However, the posterior-superior border of the septum and walls of the adjacent superior conchae are lined by a thick olfactory epithelium where olfaction, the perception of smell, occurs. Fetus 400x, 10x, 400x
Nasal septum >
The nasal septum separates the two nasal cavities (nasal fossae, NC). Cartilage forms the central frame of this fetal septum. Note that the olfactory epithelium and underlying lamina propria (green arrows) above the horizontal bar are much thicker than the corresponding layers in the respiratory region (blue arrows) below the bar.
Respiratory epithelium >
Respiratory epithelium and its underlying lamina propria, lining the nasal septum below the bar, are seen at higher magnification on the left and in the previous image.
Olfactory epithelium >
The thicker olfactory epithelium and its lamina propria, above the bar, line the superior portion of the septum and are seen at higher magnification on the right and in the next image.
Cartilage / bone >
Cartilage (black arrow) forms the framework for the septum at this stage of fetal development. Bone (blue arrows) is already being deposited along the inferior border of the septum and will replace the cartilage over time.