Olfactory cleft

Japanese: 嗅裂 - きゅうれつ

…When we inhale through our nose, the air that enters the nostrils passes mainly through the middle and inferior nasal passages into the trachea, but a small amount of air passes through the superior nasal passages. In other words, it flows into a narrow area called the olfactory cleft at the top of the nasal cavity. This is where the olfactory cells are located, and they detect odors. …

From [Nose]

…The spaces that each nasal turbinate embraces below it are called the nasal meatus, and are called the superior, middle, and inferior meatus, respectively. The nasal meatus also includes the olfactory cleft and the common meatus. The olfactory cleft is the space between the nasal septum and the middle turbinate, but only about the upper third of it is actually covered by the epithelium related to smell (olfactory epithelium). …

*Some of the terminology that mentions the olfactory cleft is listed below.

Source | Heibonsha World Encyclopedia 2nd Edition | Information

Japanese:

…鼻から空気を吸うと，鼻孔から入った空気は，おもに中，下鼻道を通って気管にゆくが，少量の空気は上鼻道を通過する。つまり鼻腔の上部にある嗅裂という狭い部分に流れこむ。ここに嗅細胞olfactory cellがあり，においを感じとっている。…