The Embryonic Development of the Human Ethmoid Labyrinth from 8-40 Weeks

Abstract

The embryonic development of the human ethmoid labyrinth was studied in 24 fetal heads aged between 8 and 40 weeks of gestation under light microscopy. The uncinate process was identifiable at 8 weeks of gestation on the laterosuperior portion of the inferior turbinate; however, at this stage of development, the ethmoid bulla was not apparent. The ethmoid bulla developed on the lateral wall of the middle meatus by 12 weeks of gestation. By 14 weeks, the primordial ethmoid infundibulum and primordial maxillary sinus were seen developing between the uncinate process and the ethmoid bulla. It was obvious that the anterior and middle ethmoid cells developed from the ethmoid bulla. By 22 weeks of gestation, the first cell of the anterior ethmoid group was evident in the anterior-inferior portion of the ethmoid bulla. By 23 weeks of gestation, the first cell of the middle ethmoid group was visible in the superior portion of the ethmoid bulla. Pneumatization of the middle turbinate occurred as part of normal development of the ethmoid labyrinth. By 32 weeks of gestation, the ostium for the development of the middle turbinate cell was seen in the superior-interior portion of the middle turbinate. These observations provide new insight into the development of the ethmoid labyrinth and have important implications for the understanding of normal anatomy and developmental variants of the ethmoid labyrinth.

Novel insights into the development of the avian nasal cavity

“…In mammals, this process is less well understood. At first glance, it would appear that mammals experience direct outgrowth of conchae from the nasal wall into a patent nasal vestibule (Smith & Rossie, 2008; Van Valkenburgh et al, 2014), including in humans (Bingham, Wang, Hawke, & Kwok, 1991; Wake, Takeno, & Hawke, 1994; Wang & Jiang, 1997). However, the human literature (which is the most extensive) on nasal plug and nasal turbinal development reveals an overlap in the timing of development of these two structures.…”

“…However, the human literature (which is the most extensive) on nasal plug and nasal turbinal development reveals an overlap in the timing of development of these two structures. In describing the developing human maxilloturbinals, several studies describe the nasal turbinals in 8‐week‐old embryos, with no mention of a nasal plugs (Bingham et al, 1991; Müller & O'Rahilly, 2004; Neskey, Eloy, & Casiano, 2009; Wake et al, 1994; Wang & Jiang, 1997). On the other hand, studies focusing on nasal plugs describe them as forming at the same developmental time points (Carnegie stage 20, ~8 weeks of gestation) with no mention of the nasal turbinals (Diewert & Shiota, 1990; Kim et al, 2004; Yoon et al, 2000).…”

Is pneumatization of middle turbinates compensatory or congenital?

“…The first accessory sinus to develop is the ethmoidal labyrinth. 5,8 Ethmoid sinus budding can be detected at 11-12 gestational weeks. 12 The ethmoidal labyrinth forms two recesses: the ethmoidofrontal and the ethmoidomaxillary.…”

“…By 32 weeks of gestation, the ostium for the development of the middle turbinate cell is seen in the superoinferior portion of the middle turbinate. 5 Although the exact mechanism of pneumatization of the turbinates has not been elucidated, two discrete hypotheses related to the development of a CB were proposed by Stammberger. 6 The first suggests that after formation of the nasal septal deviation, unfilled space ''e vacuo'' provokes the development of CB.…”

The incidence of pneumatised inferior turbinate and relation to close anatomic structures

“…The most commonly accepted hypothesis of the pathogenetic mechanisms are associated with embriological development of the inferior turbinate. Inferior turbinate develops from prochordal plaque at the 6-8 th embryonal weeks on the lateral wall of the nose [9,14]. Two chondral lamellas and 2 separate ossification centres are seen on the inferior concha at 5-7 th months [5] and the development continues after birth [2].…”