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Initial stage of fetal development of the pharyngotympanic tube cartilage with special reference to muscle attachments to the tube.

Katori Y, Rodríguez-Vázquez JF, Verdugo-López S, Murakami G, Kawase T, Kobayashi T - Anat Cell Biol (2012)

Bottom Line: In large fetuses, this loose tissue was occupied by an inferior extension of the temporal bone to cover the artery.This later-developing anterior wall of the carotid canal provided the final bony origin of the levator veli palatini muscle.Consequently, the tubal cartilage development seemed to be accelerated by a surrounding muscle, and conversely, the cartilage was likely to determine the other muscular and bony structures.

View Article: PubMed Central - PubMed

Affiliation: Division of Otorhinolaryngology, Sendai Municipal Hospital, Sendai, Japan.

ABSTRACT
Fetal development of the cartilage of the pharyngotympanic tube (PTT) is characterized by its late start. We examined semiserial histological sections of 20 human fetuses at 14-18 weeks of gestation. As controls, we also observed sections of 5 large fetuses at around 30 weeks. At and around 14 weeks, the tubal cartilage first appeared in the posterior side of the pharyngeal opening of the PTT. The levator veli palatini muscle used a mucosal fold containing the initial cartilage for its downward path to the palate. Moreover, the cartilage is a limited hard attachment for the muscle. Therefore, the PTT and its cartilage seemed to play a critical role in early development of levator veli muscle. In contrast, the cartilage developed so that it extended laterally, along a fascia-like structure that connected with the tensor tympani muscle. This muscle appeared to exert mechanical stress on the initial cartilage. The internal carotid artery was exposed to a loose tissue facing the tubal cartilage. In large fetuses, this loose tissue was occupied by an inferior extension of the temporal bone to cover the artery. This later-developing anterior wall of the carotid canal provided the final bony origin of the levator veli palatini muscle. The tubal cartilage seemed to determine the anterior and inferior margins of the canal. Consequently, the tubal cartilage development seemed to be accelerated by a surrounding muscle, and conversely, the cartilage was likely to determine the other muscular and bony structures.

No MeSH data available.


Related in: MedlinePlus

Mucosal fold of the lateral pharyngeal wall and pharyngotympanic tube cartilage: three fetuses. Azan staining. Horizontal sections. All panels exhibit the inferior part or wall of the pharyngotympanic tube (PTT). The cartilage has not yet appeared in the specimen shown in (A) (crown-rump length [CRL], 101 mm), but the levator veli palatini muscle (LVP) has begun to extend into the putative mucosal fold at the pharyngeal opening of the PTT. In (B) (CRL, 100 mm) and (C) (CRL, 116 mm), the tubal cartilage (C) is almost 2 mm in length and these panels show the medial end. The LVP employs the mucosal fold containing the cartilage to guide its downward path to the palate. A fascia (circles), along the LVP, extends posteromedially to cover the longus capitis muscle (LC, panel C). Arrows indicate another fascia along the tensor veli palatini muscle (TVP). The internal cartotid artery (ICA) is exposed to a loose space (stars) on the posterior side of the PTT. LP, lateral pterygoid muscle; MP, medial pterygoid muscle; PT, pterygoid process;TB, temporal bone. Scale bar=1 mm (A-C).
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Figure 3: Mucosal fold of the lateral pharyngeal wall and pharyngotympanic tube cartilage: three fetuses. Azan staining. Horizontal sections. All panels exhibit the inferior part or wall of the pharyngotympanic tube (PTT). The cartilage has not yet appeared in the specimen shown in (A) (crown-rump length [CRL], 101 mm), but the levator veli palatini muscle (LVP) has begun to extend into the putative mucosal fold at the pharyngeal opening of the PTT. In (B) (CRL, 100 mm) and (C) (CRL, 116 mm), the tubal cartilage (C) is almost 2 mm in length and these panels show the medial end. The LVP employs the mucosal fold containing the cartilage to guide its downward path to the palate. A fascia (circles), along the LVP, extends posteromedially to cover the longus capitis muscle (LC, panel C). Arrows indicate another fascia along the tensor veli palatini muscle (TVP). The internal cartotid artery (ICA) is exposed to a loose space (stars) on the posterior side of the PTT. LP, lateral pterygoid muscle; MP, medial pterygoid muscle; PT, pterygoid process;TB, temporal bone. Scale bar=1 mm (A-C).

Mentions: Figs. 1-3 show horizontal sections, Fig. 4 frontal sections and Fig. 5 sagittal sections. The initial appearance of the tubal cartilage is evident in Fig. 1, and a fascial connection between the cartilage and the tensor tympani muscle is evident in Figs. 1 and 2. Likewise, the topographical relationship between the cartilage and the levator veli palatini muscle is shown in Figs. 1, 3, and 4. Finally, Fig. 5 displays the pharyngeal recess. In addition, all the figures show the underdeveloped carotid canal of the temporal bone, in contrast to the late stage (Fig. 5D inset).


Initial stage of fetal development of the pharyngotympanic tube cartilage with special reference to muscle attachments to the tube.

Katori Y, Rodríguez-Vázquez JF, Verdugo-López S, Murakami G, Kawase T, Kobayashi T - Anat Cell Biol (2012)

Mucosal fold of the lateral pharyngeal wall and pharyngotympanic tube cartilage: three fetuses. Azan staining. Horizontal sections. All panels exhibit the inferior part or wall of the pharyngotympanic tube (PTT). The cartilage has not yet appeared in the specimen shown in (A) (crown-rump length [CRL], 101 mm), but the levator veli palatini muscle (LVP) has begun to extend into the putative mucosal fold at the pharyngeal opening of the PTT. In (B) (CRL, 100 mm) and (C) (CRL, 116 mm), the tubal cartilage (C) is almost 2 mm in length and these panels show the medial end. The LVP employs the mucosal fold containing the cartilage to guide its downward path to the palate. A fascia (circles), along the LVP, extends posteromedially to cover the longus capitis muscle (LC, panel C). Arrows indicate another fascia along the tensor veli palatini muscle (TVP). The internal cartotid artery (ICA) is exposed to a loose space (stars) on the posterior side of the PTT. LP, lateral pterygoid muscle; MP, medial pterygoid muscle; PT, pterygoid process;TB, temporal bone. Scale bar=1 mm (A-C).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3472145&req=5

Figure 3: Mucosal fold of the lateral pharyngeal wall and pharyngotympanic tube cartilage: three fetuses. Azan staining. Horizontal sections. All panels exhibit the inferior part or wall of the pharyngotympanic tube (PTT). The cartilage has not yet appeared in the specimen shown in (A) (crown-rump length [CRL], 101 mm), but the levator veli palatini muscle (LVP) has begun to extend into the putative mucosal fold at the pharyngeal opening of the PTT. In (B) (CRL, 100 mm) and (C) (CRL, 116 mm), the tubal cartilage (C) is almost 2 mm in length and these panels show the medial end. The LVP employs the mucosal fold containing the cartilage to guide its downward path to the palate. A fascia (circles), along the LVP, extends posteromedially to cover the longus capitis muscle (LC, panel C). Arrows indicate another fascia along the tensor veli palatini muscle (TVP). The internal cartotid artery (ICA) is exposed to a loose space (stars) on the posterior side of the PTT. LP, lateral pterygoid muscle; MP, medial pterygoid muscle; PT, pterygoid process;TB, temporal bone. Scale bar=1 mm (A-C).
Mentions: Figs. 1-3 show horizontal sections, Fig. 4 frontal sections and Fig. 5 sagittal sections. The initial appearance of the tubal cartilage is evident in Fig. 1, and a fascial connection between the cartilage and the tensor tympani muscle is evident in Figs. 1 and 2. Likewise, the topographical relationship between the cartilage and the levator veli palatini muscle is shown in Figs. 1, 3, and 4. Finally, Fig. 5 displays the pharyngeal recess. In addition, all the figures show the underdeveloped carotid canal of the temporal bone, in contrast to the late stage (Fig. 5D inset).

Bottom Line: In large fetuses, this loose tissue was occupied by an inferior extension of the temporal bone to cover the artery.This later-developing anterior wall of the carotid canal provided the final bony origin of the levator veli palatini muscle.Consequently, the tubal cartilage development seemed to be accelerated by a surrounding muscle, and conversely, the cartilage was likely to determine the other muscular and bony structures.

View Article: PubMed Central - PubMed

Affiliation: Division of Otorhinolaryngology, Sendai Municipal Hospital, Sendai, Japan.

ABSTRACT
Fetal development of the cartilage of the pharyngotympanic tube (PTT) is characterized by its late start. We examined semiserial histological sections of 20 human fetuses at 14-18 weeks of gestation. As controls, we also observed sections of 5 large fetuses at around 30 weeks. At and around 14 weeks, the tubal cartilage first appeared in the posterior side of the pharyngeal opening of the PTT. The levator veli palatini muscle used a mucosal fold containing the initial cartilage for its downward path to the palate. Moreover, the cartilage is a limited hard attachment for the muscle. Therefore, the PTT and its cartilage seemed to play a critical role in early development of levator veli muscle. In contrast, the cartilage developed so that it extended laterally, along a fascia-like structure that connected with the tensor tympani muscle. This muscle appeared to exert mechanical stress on the initial cartilage. The internal carotid artery was exposed to a loose tissue facing the tubal cartilage. In large fetuses, this loose tissue was occupied by an inferior extension of the temporal bone to cover the artery. This later-developing anterior wall of the carotid canal provided the final bony origin of the levator veli palatini muscle. The tubal cartilage seemed to determine the anterior and inferior margins of the canal. Consequently, the tubal cartilage development seemed to be accelerated by a surrounding muscle, and conversely, the cartilage was likely to determine the other muscular and bony structures.

No MeSH data available.


Related in: MedlinePlus